diff --git a/src/data.ts b/src/data.ts
index 62de2aa..7dd2e2d 100644
--- a/src/data.ts
+++ b/src/data.ts
@@ -557,7 +557,7 @@ export const topics: Topic[] = [
     index: 6,
     snapshot: "images/snapshots/topic06.png",
     essay: "pdfs/topic06.pdf",
-    animationContributors: [ZEJIN_XU],
+    animationContributors: [ZEJIN_XU, JIANLIN_LI],
     essayContributors: [ZHIQIN_LU, XIANFU_LIU],
     captionContributors: [CHEN_XU],
   },
diff --git a/src/main.ts b/src/main.ts
index 3125f13..0dfe307 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -22,7 +22,11 @@ createApp(App)
   .use(Antd)
   .directive("katex", (el, binding) => {
     const isDisplay = binding.arg === "display";
-    katex.render(el.innerHTML, el, { displayMode: isDisplay });
+    try {
+      katex.render(el.innerHTML, el, { displayMode: isDisplay });
+    } catch (e) {
+      console.error("KaTeX rendering error:", e);
+    }
   })
   .directive("tikz", (el) => {
     const scripts = el.innerHTML;
@@ -34,3 +38,5 @@ createApp(App)
     el.appendChild(scriptTag);
   })
   .mount("#app");
+
+// 函数用于解码 HTML 实体
diff --git a/src/views/TopicsView.vue b/src/views/TopicsView.vue
index d6b392b..302784f 100644
--- a/src/views/TopicsView.vue
+++ b/src/views/TopicsView.vue
@@ -1,6 +1,6 @@
 <template>
   <ATypographyTitle :level="1">Topics</ATypographyTitle>
-  <AList itemLayout="horizontal" :dataSource="topics" :grid="{gutter: 16}">
+  <AList itemLayout="horizontal" :dataSource="topics" :grid="{ gutter: 16 }">
     <template #renderItem="{ item: topic }">
       <AListItem>
         <RouterLink :to="`/topic/${topic.index}`" target="_blank">
@@ -10,7 +10,7 @@
             </template>
             <ACardMeta :title="`Topic ${topic.index}`">
               <template #description>
-                <div style="height: 3rem; width: 250px;">
+                <div style="height: 3rem; width: 250px">
                   {{ topic.name }}
                 </div>
               </template>
@@ -49,4 +49,9 @@ export default defineComponent({
   width: 300px;
   padding: 1px;
 }
+
+.animation-layout {
+  display: flex;
+  gap: 20px;
+}
 </style>
diff --git a/src/views/topics/GdpTopic06View.vue b/src/views/topics/GdpTopic06View.vue
index f355314..ba549c4 100644
--- a/src/views/topics/GdpTopic06View.vue
+++ b/src/views/topics/GdpTopic06View.vue
@@ -1,109 +1,135 @@
 <template>
   <TopicMeta :topic="topic" />
 
-  <div id="Pascal-Brainchon-wrapper" style="padding-top: 40px">
-    <ATypographyTitle :level="4">Animated Pappus' Theorem </ATypographyTitle>
-    <ATypographyParagraph class="topics-description">
-      <p>
-        Pappus' Theorem, also known as Pappus' Hexagon Theorem, is named after Greek mathematician
-        Pappus of Alexandria, who lived approximately 3rd or 4th century AD.
-      </p>
-      <p>
-        Let <span v-katex>A, B, C</span> be three points on one line (the bottom line in the
-        picture), and let <span v-katex>A', B', C'</span>be three points on another line (the top
-        line in the picture). Let <span v-katex>X, Y, Z </span> be the intersections of
-        <span v-katex>BC'</span> and <span v-katex>B'C</span>; <span v-katex>AC'</span> and
-        <span v-katex>A'C</span>; and <span v-katex>AB'</span> and <span v-katex>A'B</span>,
-        respectively. Then <span v-katex>X,Y,Z</span> are collinear.
-      </p>
-      <p>
-        Click, hold and move one of the six points <span v-katex>A,B,C,A',B',C'</span>. One can see
-        that the red line always passing points <span v-katex>X,Y,Z</span>. The red line is called
-        the Pappus Line.
-      </p>
-    </ATypographyParagraph>
-    <canvas id="Pascal-Brainchon-canvas" width="500" height="500" />
-  </div>
-
-  <div id="Pascal-wrapper" style="padding-top: 40px">
-    <ATypographyTitle :level="4"> Animated Pascal's Theorem</ATypographyTitle>
-    <ATypographyParagraph class="topics-description">
-      <p>
-        Pascal's Theorem is named after Blaise Pascal, which was formulated by Blaise Pascal in a
-        note written in 1639 when he was only 16 years old.
-      </p>
-      <p>
-        Pascal's Theorem states that if <span v-katex>ABCDEF</span> is an inscribed hexagon of a
-        circle, then the intersections <span v-katex>X, Y, Z</span> of the three pairs of the
-        opposite sides of the hexagon is collinear.
-      </p>
-      <p>
-        Click, hold, and move any of points <span v-katex>A, B, C, D, E, F</span> to observe that
-        points <span v-katex>X, Y, Z</span> are always collinear.
-      </p>
-      <p>
-        Pascal's Theorem can be generalized to the case when a hexagon is inscribed in a conic
-        curve. Since two lines can be regarded as a degenerated conic curve, Pappus' Theorem is a
-        special case of the (generalized) Pascal Theorem.
-      </p>
-    </ATypographyParagraph>
-    <canvas id="Pascal-canvas" width="500" height="500" />
-  </div>
-
-  <div id="Desargues-wrapper" style="padding-top: 40px">
-    <ATypographyTitle :level="4"> Animated Desargues' Theorem</ATypographyTitle>
-    <ATypographyParagraph class="topics-description">
-      <p>
-        Two triangles in a plane are perspective from a point <span v-katex>O</span>, called the
-        center of perspectivity, if the lines joining corresponding vertices of the triangles meet
-        at <span v-katex>O</span>. Dually, the triangles are said to be perspective from a line if
-        the points of intersection of corresponding lines all lie on one line.
-      </p>
-      <p>
-        Desargues' theorem, named after Girard Desargues, states that two triangles are perspective
-        from a point, if and only if it is perspective from a point.
-      </p>
-      <p>
-        In the following picture, assume that <span v-katex>AA', BB', CC'</span> are concurrent. Let
-        <span v-katex>P,Q,R</span> be the intersections of <span v-katex>BC</span> and
-        <span v-katex>B'C'</span>; <span v-katex>CA</span> and <span v-katex>C'A'</span>;
-        <span v-katex>AB</span> and <span v-katex>A'B'</span>, respectively. Then
-        <span v-katex>P, Q, R</span>
-        are collinear.
-      </p>
-      <p>
-        Click, hold, and move any of points <span v-katex>A, B, C </span> to observe that points
-        <span v-katex>P,Q, R</span> are always collinear.
-      </p>
-    </ATypographyParagraph>
-    <canvas id="Desargues-canvas" width="800" height="500" />
-  </div>
-
-  <div id="Brainchon-wrapper" style="padding-top: 40px">
-    <ATypographyTitle :level="4"> Animated Brainchon's Theorem</ATypographyTitle>
-    <ATypographyParagraph class="topics-description">
-      <p>
-        Brainchon's Theorem is named after French mathematician Charles Julien Brianchon. It is the
-        famous dual theorem of Pascal's Theorem. Like Pascal's Theorem, it can also be generalized
-        to the case of conic curves.
-      </p>
-      <p>
-        Brainchon's Theorem states that if <span v-katex>ABCDEF</span> is a hexagon circumscribed a
-        circle, then the main diagonals <span v-katex>AD, BE, CF</span>
-        are concurrent.
-      </p>
-      <p>
-        Click, hold, and move any of points <span v-katex>A, B, C, D, E, F</span> to observe that
-        lines <span v-katex>AD, BE, CF</span> are always concurrent. The Hexagon
-        <span v-katex>ABCDEF</span> doesn't have to be convex for the Brianchon's Theorem to hold.
-      </p>
-    </ATypographyParagraph>
-    <canvas id="Brainchon-canvas" width="500" height="500" />
-  </div>
+  <ATabs v-model:activeKey="activeKey1" @change="handleTabChange">
+    <ATabPane key="1" tab="Pappus">
+      <div id="Pascal-Brainchon-wrapper" class="animation-layout">
+        <div>
+          <canvas id="Pascal-Brainchon-canvas" width="500" height="500" />
+        </div>
+        <div>
+          <ATypographyParagraph>
+            <p>
+              Pappus' Theorem, also known as Pappus' Hexagon Theorem, is named after Greek
+              mathematician Pappus of Alexandria, who lived approximately 3rd or 4th century AD.
+            </p>
+            <p>
+              Let <span v-katex>A^{\prime}, B^{\prime}, C^{\prime}</span> be three points on one
+              line (the bottom line in the picture), and let <span v-katex>A', B', C'</span>be three
+              points on another line (the top line in the picture). Let
+              <span v-katex>X, Y, Z </span> be the intersections of <span v-katex>BC'</span> and
+              <span v-katex>B'C</span>; <span v-katex>AC'</span> and <span v-katex>A'C</span>; and
+              <span v-katex>AB'</span> and <span v-katex>A'B</span>, respectively. Then
+              <span v-katex>X,Y,Z</span> are collinear.
+            </p>
+            <p>
+              Click, hold and move one of the six points <span v-katex>A,B,C,A',B',C'</span>. One
+              can see that the red line always passing points <span v-katex>X,Y,Z</span>. The red
+              line is called the Pappus Line.
+            </p>
+          </ATypographyParagraph>
+        </div>
+      </div>
+    </ATabPane>
+
+    <ATabPane key="2" tab="Pascal">
+      <div id="Pascal-wrapper" class="animation-layout">
+        <div>
+          <canvas id="Pascal-canvas" width="500" height="500" />
+        </div>
+        <div>
+          <ATypographyParagraph>
+            <p>
+              Pascal's Theorem is named after Blaise Pascal, which was formulated by Blaise Pascal
+              in a note written in 1639 when he was only 16 years old.
+            </p>
+            <p>
+              Pascal's Theorem states that if <span v-katex>ABCDEF</span> is an inscribed hexagon of
+              a circle, then the intersections <span v-katex>X, Y, Z</span> of the three pairs of
+              the opposite sides of the hexagon is collinear.
+            </p>
+            <p>
+              Click, hold, and move any of points <span v-katex>A, B, C, D, E, F</span> to observe
+              that points <span v-katex>X, Y, Z</span> are always collinear.
+            </p>
+            <p>
+              Pascal's Theorem can be generalized to the case when a hexagon is inscribed in a conic
+              curve. Since two lines can be regarded as a degenerated conic curve, Pappus' Theorem
+              is a special case of the (generalized) Pascal Theorem.
+            </p>
+          </ATypographyParagraph>
+        </div>
+      </div>
+    </ATabPane>
+
+    <ATabPane key="3" tab="Desargues">
+      <div id="Desargues-wrapper">
+        <div>
+          <ATypographyParagraph>
+            <p>
+              Two triangles in a plane are perspective from a point <span v-katex>O</span>, called
+              the center of perspectivity, if the lines joining corresponding vertices of the
+              triangles meet at <span v-katex>O</span>. Dually, the triangles are said to be
+              perspective from a line if the points of intersection of corresponding lines all lie
+              on one line.
+            </p>
+            <p>
+              Desargues' theorem, named after Girard Desargues, states that two triangles are
+              perspective from a point, if and only if it is perspective from a point.
+            </p>
+            <p>
+              In the following picture, assume that <span v-katex>AA', BB', CC'</span> are
+              concurrent. Let <span v-katex>P,Q,R</span> be the intersections of
+              <span v-katex>BC</span> and <span v-katex>B'C'</span>; <span v-katex>CA</span> and
+              <span v-katex>C'A'</span>; <span v-katex>AB</span> and <span v-katex>A'B'</span>,
+              respectively. Then
+              <span v-katex>P, Q, R</span>
+              are collinear.
+            </p>
+            <p>
+              Click, hold, and move any of points <span v-katex>A, B, C </span> to observe that
+              points <span v-katex>P,Q, R</span> are always collinear.
+            </p>
+          </ATypographyParagraph>
+        </div>
+        <div>
+          <canvas id="Desargues-canvas" width="800" height="500" />
+        </div>
+      </div>
+    </ATabPane>
+
+    <ATabPane key="4" tab="Brainchon">
+      <div id="Brainchon-wrapper" class="animation-layout">
+        <div>
+          <canvas id="Brainchon-canvas" width="500" height="500" />
+        </div>
+        <div>
+          <ATypographyParagraph>
+            <p>
+              Brainchon's Theorem is named after French mathematician Charles Julien Brianchon. It
+              is the famous dual theorem of Pascal's Theorem. Like Pascal's Theorem, it can also be
+              generalized to the case of conic curves.
+            </p>
+            <p>
+              Brainchon's Theorem states that if <span v-katex>ABCDEF</span> is a hexagon
+              circumscribed a circle, then the main diagonals <span v-katex>AD, BE, CF</span>
+              are concurrent.
+            </p>
+            <p>
+              Click, hold, and move any of points <span v-katex>A, B, C, D, E, F</span> to observe
+              that lines <span v-katex>AD, BE, CF</span> are always concurrent. The Hexagon
+              <span v-katex>ABCDEF</span> doesn't have to be convex for the Brianchon's Theorem to
+              hold.
+            </p>
+          </ATypographyParagraph>
+        </div>
+      </div>
+    </ATabPane>
+  </ATabs>
 </template>
 
 <script lang="ts">
-import { defineComponent } from "vue";
+import { defineComponent, reactive, toRefs, onMounted, nextTick } from "vue";
 import { indexTopicMap } from "@/data";
 import { Topic } from "@/types";
 import { fabric } from "fabric";
@@ -334,1020 +360,1087 @@ function getInterByLinearEq(l1: LinearEq, l2: LinearEq): Coord {
   return coord;
 }
 
-/**
- * Part IV
- */
-function partFour() {
-  const cvsBra = new fabric.Canvas("Brainchon-canvas", {
-    selection: false,
-    backgroundColor: "floralwhite",
-  });
-  const RADIUS = 120;
-  const center = { x: 250, y: 250 } as Coord;
-  const centerPoint = makeCircle(center);
-  centerPoint.evented = false;
-
-  const circle = new fabric.Circle({
-    radius: RADIUS,
-    fill: "",
-    strokeWidth: 1,
-    stroke: "black",
-    left: center.x - RADIUS,
-    top: center.y - RADIUS,
-    hasControls: false,
-    selectable: false,
-    evented: false,
-  });
-  cvsBra.add(circle);
-
-  const taf = coordToPoint(polarToCartesian(RADIUS, 30, center));
-  const tab = coordToPoint(polarToCartesian(RADIUS, 80, center));
-  const tbc = coordToPoint(polarToCartesian(RADIUS, 120, center));
-  const tcd = coordToPoint(polarToCartesian(RADIUS, 2000, center));
-  const tde = coordToPoint(polarToCartesian(RADIUS, 280, center));
-  const tef = coordToPoint(polarToCartesian(RADIUS, -20, center));
-
-  const abLinear = getTangentLine(tab, RADIUS, center);
-  const bcLinear = getTangentLine(tbc, RADIUS, center);
-  const cdLinear = getTangentLine(tcd, RADIUS, center);
-  const deLinear = getTangentLine(tde, RADIUS, center);
-  const efLinear = getTangentLine(tef, RADIUS, center);
-  const faLinear = getTangentLine(taf, RADIUS, center);
-
-  const pa = makeCircle(getInterByLinearEq(abLinear, faLinear));
-  const pb = makeCircle(getInterByLinearEq(abLinear, bcLinear));
-  const pc = makeCircle(getInterByLinearEq(bcLinear, cdLinear));
-  const pd = makeCircle(getInterByLinearEq(cdLinear, deLinear));
-  const pe = makeCircle(getInterByLinearEq(deLinear, efLinear));
-  const pf = makeCircle(getInterByLinearEq(efLinear, faLinear));
-
-  const ab = makeLine(pa, pb);
-  const bc = makeLine(pb, pc);
-  const cd = makeLine(pd, pc);
-  const de = makeLine(pd, pe);
-  const ef = makeLine(pf, pe);
-  const fa = makeLine(pf, pa);
-
-  ab.tan = makeCircle(new fabric.Point(pa.left!, pa.top!).lerp({ x: pb.left!, y: pb.top! }, 0.5));
-  bc.tan = makeCircle(new fabric.Point(pc.left!, pc.top!).lerp({ x: pb.left!, y: pb.top! }, 0.5));
-  cd.tan = makeCircle(new fabric.Point(pc.left!, pc.top!).lerp({ x: pd.left!, y: pd.top! }, 0.5));
-  de.tan = makeCircle(new fabric.Point(pd.left!, pd.top!).lerp({ x: pe.left!, y: pe.top! }, 0.5));
-  ef.tan = makeCircle(new fabric.Point(pe.left!, pe.top!).lerp({ x: pf.left!, y: pf.top! }, 0.5));
-  fa.tan = makeCircle(new fabric.Point(pa.left!, pa.top!).lerp({ x: pf.left!, y: pf.top! }, 0.5));
-  // Tangent lines
-  ab.tan.clockLine = makeLine(ab.tan, pa);
-  ab.tan.cntClockLine = makeLine(ab.tan, pb);
-  bc.tan.clockLine = makeLine(bc.tan, pb);
-  bc.tan.cntClockLine = makeLine(bc.tan, pc);
-  cd.tan.clockLine = makeLine(cd.tan, pc);
-  cd.tan.cntClockLine = makeLine(cd.tan, pd);
-  de.tan.clockLine = makeLine(de.tan, pd);
-  de.tan.cntClockLine = makeLine(de.tan, pe);
-  ef.tan.clockLine = makeLine(ef.tan, pe);
-  ef.tan.cntClockLine = makeLine(ef.tan, pf);
-  fa.tan.clockLine = makeLine(fa.tan, pf);
-  fa.tan.cntClockLine = makeLine(fa.tan, pa);
-  ab.tan.clockLine.set({ x1: 0, y1: 0, x2: 0, y2: 0 });
-  bc.tan.clockLine.set({ x1: 0, y1: 0, x2: 0, y2: 0 });
-  cd.tan.clockLine.set({ x1: 0, y1: 0, x2: 0, y2: 0 });
-  de.tan.clockLine.set({ x1: 0, y1: 0, x2: 0, y2: 0 });
-  ef.tan.clockLine.set({ x1: 0, y1: 0, x2: 0, y2: 0 });
-  fa.tan.clockLine.set({ x1: 0, y1: 0, x2: 0, y2: 0 });
-  [ab, bc, cd, de, ef, fa].forEach((line) => {
-    if (line.tan !== undefined) {
-      line.tan.clockLine?.set({ strokeDashArray: [10], stroke: "Aqua" });
-      line.tan.cntClockLine?.set({ strokeDashArray: [10], stroke: "Aqua" });
-      // line.tan.clockLine?.set({x1: 0, y1: 0, x2: 0, y2: 0});
-      // line.tan.cntClockLine?.set({x1: 0, y1: 0, x2: 0, y2: 0});
-      cvsBra.add(line.tan.clockLine!, line.tan.cntClockLine!);
-    }
-  });
-
-  const ad = makeLine(pa, pd, undefined, "green");
-  const be = makeLine(pb, pe, undefined, "green");
-  const cf = makeLine(pc, pf, undefined, "green");
-  Object.assign(ad, solveLinearEquation({ x: ad.x1!, y: ad.y1! }, { x: ad.x2!, y: ad.y2! }));
-  Object.assign(be, solveLinearEquation({ x: be.x1!, y: be.y1! }, { x: be.x2!, y: be.y2! }));
-  const intersection = makeCircle(
-    getInterByLinearEq({ m: ad.m!, b: ad.b! }, { m: be.m!, b: be.b! }),
-    3,
-    "red"
-  );
-  intersection.set({ selectable: false, evented: false });
-  const ia = makeLine(intersection, pa, undefined, "green");
-  const ib = makeLine(intersection, pb, undefined, "green");
-  const ic = makeLine(intersection, pc, undefined, "green");
-  const id = makeLine(intersection, pd, undefined, "green");
-  const ie = makeLine(intersection, pe, undefined, "green");
-  const iF = makeLine(intersection, pf, undefined, "green");
-
-  pa.clockLine = fa;
-  pa.cntClockLine = ab;
-  pb.clockLine = ab;
-  pb.cntClockLine = bc;
-  pc.clockLine = bc;
-  pc.cntClockLine = cd;
-  pd.clockLine = cd;
-  pd.cntClockLine = de;
-  pe.clockLine = de;
-  pe.cntClockLine = ef;
-  pf.clockLine = ef;
-  pf.cntClockLine = fa;
-
-  pa.clockPoint = pf;
-  pa.cntClockPoint = pb;
-  pb.clockPoint = pa;
-  pb.cntClockPoint = pc;
-  pc.clockPoint = pb;
-  pc.cntClockPoint = pd;
-  pd.clockPoint = pc;
-  pd.cntClockPoint = pe;
-  pe.clockPoint = pd;
-  pe.cntClockPoint = pf;
-  pf.clockPoint = pe;
-  pf.cntClockPoint = pa;
-
-  ab.p1 = pa;
-  ab.p2 = pb;
-  bc.p1 = pb;
-  bc.p2 = pc;
-  cd.p1 = pc;
-  cd.p2 = pd;
-  de.p1 = pd;
-  de.p2 = pe;
-  ef.p1 = pe;
-  ef.p2 = pf;
-  fa.p1 = pa;
-  fa.p2 = pf;
-  ad.p1 = pa;
-  ad.p2 = pd;
-  be.p1 = pb;
-  be.p2 = pe;
-  cf.p1 = pc;
-  cf.p2 = pf;
-  ia.p1 = pa;
-  ib.p1 = pb;
-  ic.p1 = pc;
-  id.p1 = pd;
-  ie.p1 = pe;
-  iF.p1 = pf;
-
-  const aLabel = makeLabel("A", { x: 10, y: -20 });
-  const bLabel = makeLabel("B", { x: 0, y: -30 });
-  const cLabel = makeLabel("C", { x: -25, y: -5 });
-  const dLabel = makeLabel("D", { x: -5, y: 10 });
-  const eLabel = makeLabel("E");
-  const fLabel = makeLabel("F");
-  const oLabel = makeLabel("O");
-  setLabelToPoint(
-    [aLabel, bLabel, cLabel, dLabel, eLabel, fLabel, oLabel],
-    [pa, pb, pc, pd, pe, pf, centerPoint]
-  );
-  cvsBra.add(aLabel, bLabel, cLabel, dLabel, eLabel, fLabel, oLabel);
-  cvsBra.add(pa, pb, pc, pd, pe, pf, centerPoint);
-  cvsBra.add(ia, ib, ic, id, ie, iF);
-  cvsBra.add(intersection);
-  cvsBra.add(ab, bc, cd, de, ef, fa);
-
-  const onPointMove = (e: IEvent): void => {
-    const p = e.target! as Circle;
-    let dist = calculateDistanceBetweenTwoPoints(circleToCoord(p)[0], center);
-    const offset = 10;
-    if (dist <= RADIUS + offset) {
-      dist = RADIUS + offset;
-    }
-    const alpha = Math.acos(RADIUS / dist);
-    let rad = Math.atan(-findSlope([center.x, center.y], [p.left!, p.top!]));
-
-    if (p.left! < center.x) {
-      rad -= Math.PI;
-    }
-    // Restrict movement outside of circle.
-    if (dist <= RADIUS + offset) {
-      const onCircle = polarToCartesian(RADIUS + offset, rad, center, false);
-      p.set({ left: onCircle.x, top: onCircle.y });
-    }
-    setLabelToPoint([p.label!], [p]);
-    const clkRad = rad - alpha;
-    const cntClkRad = alpha + rad;
-    // New tangent point and lines
-    const clkT = polarToCartesian(RADIUS, clkRad, center, false);
-    const cntClkT = polarToCartesian(RADIUS, cntClkRad, center, false);
-    // Update closest tangent points.
-    p.clockLine!.tan!.set({ left: clkT.x, top: clkT.y });
-    p.cntClockLine!.tan!.set({ left: cntClkT.x, top: cntClkT.y });
-    const clkLinearEq = solveLinearEquation(circleToCoord(p)[0], clkT);
-    const cntClkLinearEq = solveLinearEquation(circleToCoord(p)[0], cntClkT);
-
-    // New intersections
-    let clkLine = p.clockPoint!.clockLine!;
-    let cntClkLine = p.cntClockPoint!.cntClockLine!;
-    const clkP = getInterByLinearEq(
-      clkLinearEq,
-      solveLinearEquation({ x: clkLine.x1!, y: clkLine.y1! }, { x: clkLine.x2!, y: clkLine.y2! })
-    );
-    p.clockPoint!.set({ left: clkP.x, top: clkP.y });
-    const cntClkP = getInterByLinearEq(
-      cntClkLinearEq,
-      solveLinearEquation(
-        { x: cntClkLine.x1!, y: cntClkLine.y1! },
-        { x: cntClkLine.x2!, y: cntClkLine.y2! }
-      )
-    );
-    p.cntClockPoint!.set({ left: cntClkP.x, top: cntClkP.y });
-
-    // Update lines accordingly
-    setLineFromPoints(
-      clkLine,
-      { x: clkLine.p1!.left!, y: clkLine.p1!.top! },
-      { x: clkLine.p2!.left!, y: clkLine.p2!.top! }
-    );
-    setLineFromPoints(
-      cntClkLine,
-      { x: cntClkLine.p1!.left!, y: cntClkLine.p1!.top! },
-      { x: cntClkLine.p2!.left!, y: cntClkLine.p2!.top! }
-    );
-    // clkLine.tan!.set();
-    // Update strokes
-    [clkLine, cntClkLine].forEach((line) => {
-      if (
-        line.tan !== undefined &&
-        line.tan.clockLine !== undefined &&
-        line.tan.cntClockLine !== undefined
-      ) {
-        setLineFromPoints(
-          line.tan.clockLine,
-          { x: line.tan.clockLine.p1!.left!, y: line.tan.clockLine.p1!.top! },
-          { x: line.tan.clockLine.p2!.left!, y: line.tan.clockLine.p2!.top! }
-        );
-        setLineFromPoints(
-          line.tan.cntClockLine,
-          { x: line.tan.cntClockLine.p1!.left!, y: line.tan.cntClockLine.p1!.top! },
-          { x: line.tan.cntClockLine.p2!.left!, y: line.tan.cntClockLine.p2!.top! }
-        );
-      }
-    });
-
-    clkLine = p.clockLine!;
-    setLineFromPoints(
-      clkLine,
-      { x: clkLine.p1!.left!, y: clkLine.p1!.top! },
-      { x: clkLine.p2!.left!, y: clkLine.p2!.top! }
-    );
-    cntClkLine = p.cntClockLine!;
-    setLineFromPoints(
-      cntClkLine,
-      { x: cntClkLine.p1!.left!, y: cntClkLine.p1!.top! },
-      { x: cntClkLine.p2!.left!, y: cntClkLine.p2!.top! }
-    );
-    // Update intersections
-    [ad, be].forEach((line) => {
-      setLineFromPoints(
-        line,
-        { x: line.p1!.left!, y: line.p1!.top! },
-        { x: line.p2!.left!, y: line.p2!.top! }
-      );
-    });
-    [clkLine, cntClkLine].forEach((line) => {
-      if (
-        line.tan !== undefined &&
-        line.tan.clockLine !== undefined &&
-        line.tan.cntClockLine !== undefined
-      ) {
-        setLineFromPoints(
-          line.tan.clockLine,
-          { x: line.tan.clockLine.p1!.left!, y: line.tan.clockLine.p1!.top! },
-          { x: line.tan.clockLine.p2!.left!, y: line.tan.clockLine.p2!.top! }
-        );
-        setLineFromPoints(
-          line.tan.cntClockLine,
-          { x: line.tan.cntClockLine.p1!.left!, y: line.tan.cntClockLine.p1!.top! },
-          { x: line.tan.cntClockLine.p2!.left!, y: line.tan.cntClockLine.p2!.top! }
-        );
-      }
+export default defineComponent({
+  setup() {
+    const state = reactive({
+      topic,
+      activeKey1: "1",
+      firstCanvas: false,
+      secondCanvas: false,
+      thirdCanvas: false,
+      fouthCanvas: false,
     });
 
-    Object.assign(ad, solveLinearEquation({ x: ad.x1!, y: ad.y1! }, { x: ad.x2!, y: ad.y2! }));
-    Object.assign(be, solveLinearEquation({ x: be.x1!, y: be.y1! }, { x: be.x2!, y: be.y2! }));
-    const updateInter = getInterByLinearEq({ m: ad.m!, b: ad.b! }, { m: be.m!, b: be.b! });
-    intersection.set({ left: updateInter.x, top: updateInter.y });
-    [ia, ib, ic, id, ie, iF].forEach((line) =>
-      setLineFromPoints(
-        line,
-        { x: line.p1!.left!, y: line.p1!.top! },
-        { x: intersection.left!, y: intersection.top! }
-      )
-    );
-
-    setLabelToPoint(
-      [p.clockPoint!.label!, p.cntClockPoint!.label!],
-      [p.clockPoint!, p.cntClockPoint!]
-    );
-  };
-
-  cvsBra.on("object:moving", onPointMove);
-}
-
-/**
- * Part III
- */
-function partThree() {
-  const cvsDes = new fabric.Canvas("Desargues-canvas", {
-    selection: false,
-    backgroundColor: "floralwhite",
-  });
-  /**
-   * Position initialization.
-   */
-  const cvsWidth = 800;
-  // (2,5.5)--(0,6)--(1.5,4)
-  const mul = 50;
-  const yOffset = 470;
-  const xOffset = 75;
-  const pointC = makeCircle(xOffset + 2 * mul, yOffset - 5.5 * mul);
-  const pointB = makeCircle(xOffset + 0 * mul, yOffset - 6 * mul);
-  const pointA = makeCircle(xOffset + 1.5 * mul, yOffset - 4 * mul);
-  // (5.5,1.125)--(0,0)--(2.25,2)
-  const pointPrimeC = makeCircle(xOffset + mul * 5.5, yOffset - mul * 1.125, 1, undefined);
-  const pointPrimeB = makeCircle(xOffset + mul * 0, yOffset - mul * 0, 1, undefined);
-  const pointPrimeA = makeCircle(xOffset + mul * 2.25, yOffset - mul * 2, 1, undefined);
-  const abc = new fabric.Polygon(circleToCoord(pointA, pointB, pointC), { fill: "yellow" });
-  const primeTriangle = new fabric.Polygon(circleToCoord(pointPrimeA, pointPrimeB, pointPrimeC), {
-    fill: "#5efc03",
-  });
-  abc.selectable = false;
-  abc.evented = false;
-  primeTriangle.selectable = false;
-  primeTriangle.evented = false;
-  cvsDes.add(abc, primeTriangle);
-  cvsDes.add(pointA, pointB, pointC, pointPrimeA, pointPrimeB, pointPrimeC);
-
-  const aLabel = makeLabel("A", { x: 15, y: -10 });
-  const bLabel = makeLabel("B", { x: -18, y: 5 });
-  const cLabel = makeLabel("C", { x: 15, y: -20 });
-  const aprimeLabel = makeLabel("A'", { x: -10, y: 5 });
-  const bprimeLabel = makeLabel("B'");
-  const cprimeLabel = makeLabel("C'");
-  const movablePoints = [pointA, pointB, pointC, pointPrimeA, pointPrimeB, pointPrimeC];
-  setLabelToPoint([aLabel, bLabel, cLabel, aprimeLabel, bprimeLabel, cprimeLabel], movablePoints);
-  // const pointsFromMovables = movablePoints.map(ele => new fabric.Point(ele.left!, ele.top!));
-  // const [pa, pb, pc, ppa, ppb, ppc] = pointsFromMovables;
-  cvsDes.add(aLabel, bLabel, cLabel, aprimeLabel, bprimeLabel, cprimeLabel);
-
-  const aAprime = makeLine(pointA, pointPrimeA);
-  const bBprime = makeLine(pointB, pointPrimeB);
-  // const cCprime = makeLine(pointC, pointPrimeC);
-  // cvsDes.add(aAprime, bBprime, cCprime);
-  const pO = calculateLineIntersectInPoints(aAprime, bBprime, true);
-  const pointO = makeCircle(pO!, 0.5);
-  const oBp = makeLine(pointO, pointPrimeB);
-  const oCp = makeLine(pointO, pointPrimeC);
-  const oAp = makeLine(pointO, pointPrimeA);
-  pointB.moveLine = oBp;
-  pointA.moveLine = oAp;
-  pointC.moveLine = oCp;
-  pointA.upBound = pointPrimeA;
-  pointA.downBound = pointO;
-  pointB.upBound = pointPrimeB;
-  pointB.downBound = pointO;
-  pointC.upBound = pointPrimeC;
-  pointC.downBound = pointO;
-  Object.assign(
-    oAp,
-    solveLinearEquation(
-      { x: pointO.left!, y: pointO.top! },
-      { x: pointPrimeA.left!, y: pointPrimeA.top! }
-    )
-  );
-  Object.assign(
-    oBp,
-    solveLinearEquation(
-      { x: pointO.left!, y: pointO.top! },
-      { x: pointPrimeB.left!, y: pointPrimeB.top! }
-    )
-  );
-  Object.assign(
-    oCp,
-    solveLinearEquation(
-      { x: pointO.left!, y: pointO.top! },
-      { x: pointPrimeC.left!, y: pointPrimeC.top! }
-    )
-  );
-  cvsDes.add(pointO, oBp, oCp, oAp);
-  // Triangle part
-  const ab = makeLine(pointA, pointB);
-  const ac = makeLine(pointA, pointC);
-  const bc = makeLine(pointB, pointC);
-  const apBp = makeLine(pointPrimeA, pointPrimeB);
-  const apCp = makeLine(pointPrimeA, pointPrimeC);
-  const bpCp = makeLine(pointPrimeB, pointPrimeC);
-  cvsDes.add(ab, ac, bc, apBp, apCp, bpCp);
-  // Assign respective lines and points
-  Object.assign(ab, {
-    p1: pointA,
-    p2: pointB,
-    thatLine: apBp,
-  });
-  Object.assign(ac, {
-    p1: pointA,
-    p2: pointC,
-    thatLine: apCp,
-  });
-  Object.assign(bc, {
-    p1: pointC,
-    p2: pointB,
-    thatLine: bpCp,
-  });
-  Object.assign(apBp, {
-    p1: pointPrimeA,
-    p2: pointPrimeB,
-    thatLine: ab,
-  });
-  Object.assign(apCp, {
-    p1: pointPrimeA,
-    p2: pointPrimeC,
-    thatLine: ac,
-  });
-  Object.assign(bpCp, {
-    p1: pointPrimeC,
-    p2: pointPrimeB,
-    thatLine: bc,
-  });
-  pointA.crossLines = [ab, ac];
-  pointB.crossLines = [ab, bc];
-  pointC.crossLines = [ac, bc];
-
-  // Collinear & cocurrent
-  const pointP = makeCircle(calculateLineIntersectInPoints(bc, bpCp, true)!, 0.5);
-  const cp = makeLine(pointC, pointP);
-  const cpP = makeLine(pointPrimeC, pointP);
-
-  const pointQ = makeCircle(calculateLineIntersectInPoints(ac, apCp, true)!, 0.5);
-  const pointR = makeCircle(calculateLineIntersectInPoints(ab, apBp, true)!, 0.5);
-  const aq = makeLine(pointA, pointQ);
-  const apQ = makeLine(pointPrimeA, pointQ);
-  const ar = makeLine(pointA, pointR);
-  const apR = makeLine(pointPrimeA, pointR);
-  const pq = makeLine(pointP, pointQ);
-  pq.p1 = pointP;
-  pq.p2 = pointQ;
-  cvsDes.add(cp, cpP, aq, apQ, ar, apR, pq);
-  cvsDes.add(pointP, pointQ, pointR);
-  // Assigning intersections
-  ab.inter = pointR;
-  apBp.inter = pointR;
-  ac.inter = pointQ;
-  apCp.inter = pointQ;
-  bc.inter = pointP;
-  bpCp.inter = pointP;
-  // Intersection lines
-  pointR.crossLines = [ar, apR];
-  ar.p1 = pointA;
-  ar.p2 = pointR;
-  apR.p1 = pointPrimeA;
-  apR.p2 = pointR;
-  pointQ.crossLines = [aq, apQ];
-  aq.p1 = pointQ;
-  aq.p2 = pointA;
-  apQ.p1 = pointPrimeA;
-  apQ.p2 = pointQ;
-  pointP.crossLines = [cp, cpP];
-  cp.p1 = pointC;
-  cp.p2 = pointP;
-  cpP.p1 = pointPrimeC;
-  cpP.p2 = pointP;
-  const oLabel = makeLabel("O", { x: -5, y: -30 });
-  const pLabel = makeLabel("P");
-  const qLabel = makeLabel("Q", { x: -25, y: 0 });
-  const rLabel = makeLabel("R", { x: 10, y: 0 });
-  setLabelToPoint([oLabel, pLabel, qLabel, rLabel], [pointO, pointP, pointQ, pointR]);
-  cvsDes.add(oLabel, pLabel, qLabel, rLabel);
-  [pointPrimeA, pointPrimeB, pointPrimeC, pointO, pointP, pointQ, pointR].forEach((p) => {
-    p.set({ lockMovementX: true, lockMovementY: true, evented: false });
-  });
-
-  // Interaction
-  const onPointMove = (e: IEvent): void => {
-    const p = e.target! as Circle;
-    // Restrict movement to line
-    if (p.moveLine !== undefined) {
-      // Restric boundries
-      if (p.upBound !== undefined && p.top! > p.upBound.top!) p.top = p.upBound.top;
-      if (p.downBound !== undefined && p.top! < p.downBound.top!) p.top = p.downBound.top;
-      let x = (p.top! - p.moveLine.b!) / p.moveLine.m!;
-      if (p.moveLine.m === Infinity) x = p.moveLine.x1!;
-      p.set("left", x);
-    }
-    abc.set("points", circleToCoord(pointA, pointB, pointC));
-
-    if (p.crossLines !== undefined) {
-      p.crossLines.forEach((line) => {
-        // Adjust line position
-        line.set({
-          x1: line.p1!.left,
-          y1: line.p1!.top,
-          x2: line.p2!.left,
-          y2: line.p2!.top,
-        });
-        // Adjust intersections accordingly
-        if (line.inter !== undefined && line.inter.crossLines !== undefined) {
-          updateInterAndLine(line, line.thatLine!, line.inter);
-          setLabelToPoint([line.inter.label!], [line.inter]);
+    function handleTabChange(activeKey: string) {
+      state.activeKey1 = activeKey;
+      nextTick(() => {
+        switch (activeKey) {
+          case "1":
+            partOne();
+            break;
+          case "2":
+            partTwo();
+            break;
+          case "3":
+            partThree();
+            break;
+          case "4":
+            partFour();
+            break;
+          default:
+            break;
         }
       });
     }
-    // Update the collinear PQ line
-    // Extend to canvas width
-    Object.assign(
-      pq,
-      solveLinearEquation({ x: pq.p1!.left!, y: pq.p1!.top! }, { x: pq.p2!.left!, y: pq.p2!.top! })
-    );
-    pq.set({
-      x1: 0,
-      y1: pq.b,
-      x2: cvsWidth,
-      y2: cvsWidth * pq.m! + pq.b!,
-    });
-    // Update according to position change
-    if (p.label !== undefined) {
-      setLabelToPoint([p.label], [p]);
-    }
-  };
-  cvsDes.on("object:moving", onPointMove);
-}
-
-/**
- * Part II
- */
+    /**
+     * Part I
+     */
 
-function partTwo() {
-  const cvsPascal = new fabric.Canvas("Pascal-canvas", {
-    selection: false,
-    backgroundColor: "aliceblue",
-  });
-  const RADIUS = 80;
-  const center = { x: 150, y: 350 } as Coord;
-  let pointA = coordToPoint(polarToCartesian(RADIUS, 10, center));
-  let pointB = coordToPoint(polarToCartesian(RADIUS, 45, center));
-  let pointC = coordToPoint(polarToCartesian(RADIUS, 80, center));
-  let pointD = coordToPoint(polarToCartesian(RADIUS, 110, center));
-  let pointE = coordToPoint(polarToCartesian(RADIUS, 225, center));
-  let pointF = coordToPoint(polarToCartesian(RADIUS, 310, center));
-
-  const aLabel = makeLabel("A", { x: 5, y: -10 });
-  const bLabel = makeLabel("B", { x: -20, y: 0 });
-  const cLabel = makeLabel("C", { x: -10, y: 10 });
-  const dLabel = makeLabel("D", { x: -35, y: -20 });
-  const eLabel = makeLabel("E", { x: -10, y: 5 });
-  const fLabel = makeLabel("F", { x: 1, y: 10 });
-  setLabelToPoint(
-    [aLabel, bLabel, cLabel, dLabel, eLabel, fLabel],
-    [pointA, pointB, pointC, pointD, pointE, pointF]
-  );
-  cvsPascal.add(aLabel, bLabel, cLabel, dLabel, eLabel, fLabel);
-
-  const circle = new fabric.Circle({
-    radius: RADIUS,
-    fill: "",
-    strokeWidth: 1,
-    stroke: "black",
-    left: center.x - RADIUS,
-    top: center.y - RADIUS,
-    hasControls: false,
-    selectable: false,
-  });
-  cvsPascal.add(circle);
-
-  const xLable = makeLabel("X", { x: 0, y: -30 });
-  const yLable = makeLabel("Y", { x: -15, y: 0 });
-  const zLable = makeLabel("Z", { x: 5, y: -25 });
-  const pointX = new fabric.Point(0, 0);
-  const pointY = new fabric.Point(0, 0);
-  const pointZ = new fabric.Point(0, 0);
-  const xy = makeLine(pointX, pointY, 1, "red");
-
-  function createLine(points?: number[], color?: string, strokeWidth?: number) {
-    return new fabric.Line(points || [], {
-      originX: "center",
-      originY: "center",
-      hasControls: false,
-      hasBorders: false,
-      evented: false,
-      stroke: color || "black",
-      strokeWidth: strokeWidth || 1,
-    });
-  }
-  const dx = makeLine(pointX, pointD, 1, "blue");
-  const bx = makeLine(pointB, pointX, 1, "blue");
-  const cz = makeLine(pointC, pointZ, 1, "blue");
-  const az = makeLine(pointA, pointZ, 1, "blue");
-  const by = makeLine(pointB, pointY, 1, "blue");
-  const fy = makeLine(pointF, pointY, 1, "blue");
-
-  function circleRestrict(p: fabric.Point): fabric.Point {
-    let rad = Math.atan(-findSlope([center.x, center.y], [p.x, p.y]));
-    if (p.x < center.x) {
-      rad -= Math.PI;
-    }
-    const coord = polarToCartesian(RADIUS, rad, center, false);
-    p.setFromPoint(coord);
-    return p;
-  }
+    function partOne() {
+      if (state.firstCanvas) return;
+      const canvas = new fabric.Canvas("Pascal-Brainchon-canvas", {
+        selection: false,
+        backgroundColor: "floralwhite",
+      });
 
-  const pa = makeCircle(pointA);
-  const pb = makeCircle(pointB);
-  const pc = makeCircle(pointC);
-  const pd = makeCircle(pointD);
-  const pe = makeCircle(pointE);
-  const pf = makeCircle(pointF);
-  const circles = [pa, pb, pc, pd, pe, pf];
-  cvsPascal.add(pa, pb, pc, pd, pe, pf);
-
-  const poly = makeMovablePolygon(
-    [pointA, pointB, pointC, pointD, pointE, pointF],
-    function (coords: fabric.Point[]) {
-      [pointA, pointB, pointC, pointD, pointE, pointF] = coords;
-      for (let idx = 0; idx < coords.length; idx++) {
-        const c = circles[idx];
-        const coord = coords[idx];
-        c.set({ left: coord.x, top: coord.y });
-      }
-      setLabelToPoint([aLabel, bLabel, cLabel, dLabel, eLabel, fLabel], coords);
-      pointX.setFromPoint(
-        calculateLineIntersectInPoints(
-          // de - ab
-          makeLine(pointD, pointE),
-          makeLine(pointA, pointB),
-          true
-        ) as fabric.Point
+      const bottomLine = new fabric.Line([0, 400, 500, 400], {
+        // # TODO use reduce
+        stroke: "black",
+        hasControls: false,
+        hasBorders: false,
+        evented: false,
+        strokeWidth: 2,
+      }) as Line;
+      Object.assign(
+        bottomLine,
+        solveLinearEquation(
+          new fabric.Point(bottomLine.x1!, bottomLine.y1!),
+          new fabric.Point(bottomLine.x2!, bottomLine.y2!)
+        )
       );
-      pointY.setFromPoint(
-        calculateLineIntersectInPoints(
-          // ef - bc
-          makeLine(pointF, pointE),
-          makeLine(pointC, pointB),
-          true
-        ) as fabric.Point
+      // y = -0.12x + 100
+      const upperLine = new fabric.Line([0, 130, 500, 40], {
+        stroke: "black",
+        hasControls: false,
+        hasBorders: false,
+        evented: false,
+        strokeWidth: 2,
+      }) as Line;
+      Object.assign(
+        upperLine,
+        solveLinearEquation(
+          new fabric.Point(upperLine.x1!, upperLine.y1!),
+          new fabric.Point(upperLine.x2!, upperLine.y2!)
+        )
       );
-      pointZ.setFromPoint(
-        calculateLineIntersectInPoints(
-          // af - dc
-          makeLine(pointF, pointA),
-          makeLine(pointC, pointD),
-          true
-        ) as fabric.Point
+
+      const aLabel = makeLabel("A", { x: -20, y: 15 });
+      const bLabel = makeLabel("B", { x: 0, y: 15 });
+      const cLabel = makeLabel("C", { x: 5, y: 15 });
+      const aprimeLabel = makeLabel("A'", { x: -20, y: -40 });
+      const bprimeLabel = makeLabel("B'", { x: 0, y: -40 });
+      const cprimeLabel = makeLabel("C'", { x: 0, y: -40 });
+      const xLabel = makeLabel("X", { x: 20, y: 0 });
+      const yLabel = makeLabel("Y", { x: -5, y: 5 });
+      const zLabel = makeLabel("Z", { x: -30, y: 0 });
+
+      // updated each point below (for Picture 1) to have radius 3, although it seems that makeCircle function already defaults radius 3 and padding 20
+      const pointA = makeCircle(50, 400, 3);
+      const pointB = makeCircle(250, 400, 3);
+      const pointC = makeCircle(450, 400, 3);
+      const pointPrimeA = makeCircle(50, upperLine.m! * 50 + upperLine.b!, 3);
+      const pointPrimeB = makeCircle(250, upperLine.m! * 250 + upperLine.b!, 3);
+      const pointPrimeC = makeCircle(450, upperLine.m! * 450 + upperLine.b!, 3);
+
+      const movablePoints = [pointA, pointB, pointC, pointPrimeA, pointPrimeB, pointPrimeC];
+
+      setLabelToPoint(
+        [aLabel, bLabel, cLabel, aprimeLabel, bprimeLabel, cprimeLabel],
+        movablePoints
       );
-      setLabelToPoint([xLable, yLable, zLable], [pointX, pointY, pointZ]);
-      setLineFromPoints(dx, pointX, pointD);
-      setLineFromPoints(bx, pointB, pointX);
-      setLineFromPoints(cz, pointC, pointZ);
-      setLineFromPoints(az, pointA, pointZ);
-      setLineFromPoints(by, pointB, pointY);
-      setLineFromPoints(fy, pointF, pointY);
-      const { m, b } = solveLinearEquation(pointX, pointY);
-      const y1 = m * 500 + b;
-      setLineFromPoints(xy, { x: 500, y: y1 }, { x: 0, y: b });
-    },
-    circleRestrict
-  );
-  cvsPascal.add(dx, bx, cz, az, by, fy, xy);
-  cvsPascal.add(poly, xLable, yLable, zLable);
-
-  function _polygonPositionHandler(fn?: (points: fabric.Point[]) => void) {
-    return function (
-      this: { pointIndex: number },
-      _dim: any,
-      _finalMatrix: any,
-      fabricObject: fabric.Polygon
-    ) {
-      const c = fabricObject.points!.map(function (pt: fabric.Point) {
-        const transformPoint = new fabric.Point(
-          pt.x - fabricObject.pathOffset.x,
-          pt.y - fabricObject.pathOffset.y
-        );
-        return fabric.util.transformPoint(
-          transformPoint,
-          fabric.util.multiplyTransformMatrices(
-            fabricObject.canvas!.viewportTransform!,
-            fabricObject.calcTransformMatrix()
-          )
-        );
+
+      const pointsFromMovables = movablePoints.map((ele) => new fabric.Point(ele.left!, ele.top!));
+      const [pA, pB, pC, ppA, ppB, ppC] = pointsFromMovables;
+      const aBprime = makeLine(pA, ppB, undefined, "blue");
+      const aCprime = makeLine(pA, ppC, undefined, "blue");
+      const bAprime = makeLine(pB, ppA, undefined, "blue");
+      const bCprime = makeLine(pB, ppC, undefined, "blue");
+      const cAprime = makeLine(pC, ppA, undefined, "blue");
+      const cBprime = makeLine(pC, ppB, undefined, "blue");
+
+      const pZ = fabric.Intersection.intersectLineLine(pA, ppB, ppA, pB).points![0];
+
+      const pY = (fabric.Intersection.intersectLineLine(pA, ppC, ppA, pC) as Intersection)
+        .points![0];
+      const pX = (fabric.Intersection.intersectLineLine(pB, ppC, pC, ppB) as Intersection)
+        .points![0];
+      const [pointX, pointY, pointZ] = [pX, pY, pZ].map((p) => makeCircle(p, 0.5, 0));
+      // set fill to red for points X, Y, Z
+      pointX.fill = "red";
+      pointY.fill = "red";
+      pointZ.fill = "red";
+      // Disable user dragging on intersections
+      pointX.set({ lockMovementX: true, lockMovementY: true });
+      pointY.set({ lockMovementX: true, lockMovementY: true });
+      pointZ.set({ lockMovementX: true, lockMovementY: true });
+
+      setLabelToPoint([zLabel, yLabel, xLabel], [pointZ, pointY, pointX]);
+
+      pointA.rightBound = pointB;
+      pointB.leftBound = pointA;
+      pointB.rightBound = pointC;
+      pointC.leftBound = pointB;
+      pointPrimeA.rightBound = pointPrimeB;
+      pointPrimeB.leftBound = pointPrimeA;
+      pointPrimeB.rightBound = pointPrimeC;
+      pointPrimeC.leftBound = pointPrimeB;
+
+      const COLL_OFF_SET = 100;
+      const collinearLine = makeLine(pZ, pX, 2, "red") as Line;
+      collinearLine.p1 = pointZ;
+      collinearLine.p2 = pointX;
+      Object.assign(
+        collinearLine,
+        solveLinearEquation(
+          new fabric.Point(collinearLine.p1!.left!, collinearLine.p1!.top!),
+          new fabric.Point(collinearLine.p2!.left!, collinearLine.p2!.top!)
+        )
+      );
+      collinearLine.set({
+        x1: collinearLine.p1!.left! - COLL_OFF_SET,
+        y1: collinearLine.m! * (collinearLine.p1!.left! - COLL_OFF_SET) + collinearLine.b!,
+        x2: collinearLine.p2!.left! + COLL_OFF_SET,
+        y2: collinearLine.m! * (collinearLine.p2!.left! + COLL_OFF_SET) + collinearLine.b!,
       });
-      if (fn !== undefined) {
-        fn(c);
-      }
-      return c[this.pointIndex];
-    };
-  }
 
-  function _actionHandler(
-    _eventData: any,
-    transform: fabric.Transform,
-    x: number,
-    y: number,
-    fn: (p: fabric.Point) => fabric.Point
-  ) {
-    type MyFabricObject = fabric.Polygon & { __corner: any };
-    const polygon = transform.target as MyFabricObject;
-    const currentControl: any = polygon.controls[polygon.__corner];
-    const mouseLocalPosition = polygon.toLocalPoint(new fabric.Point(x, y), "center", "center");
-    const polygonBaseSize = polygon._getNonTransformedDimensions();
-    const size = polygon._getTransformedDimensions(0, 0);
-    const finalPointPosition = new fabric.Point(
-      (mouseLocalPosition.x * polygonBaseSize.x) / size.x + polygon.pathOffset.x,
-      (mouseLocalPosition.y * polygonBaseSize.y) / size.y + polygon.pathOffset.y
-    );
-    polygon.points![currentControl.pointIndex] = fn(finalPointPosition);
-    return true;
-  }
+      // Bind related lines and intersects to points
+      pointA.upLine = [aBprime, aCprime];
+      pointA.intersects = [pointZ, pointY];
+      pointB.upLine = [bAprime, bCprime];
+      pointB.intersects = [pointZ, pointX];
+      pointC.upLine = [cAprime, cBprime];
+      pointC.intersects = [pointY, pointX];
+      pointPrimeA.downLine = [bAprime, cAprime];
+      pointPrimeA.intersects = [pointZ, pointY];
+      pointPrimeB.downLine = [aBprime, cBprime];
+      pointPrimeB.intersects = [pointZ, pointX];
+      pointPrimeC.downLine = [aCprime, bCprime];
+      pointPrimeC.intersects = [pointY, pointX];
+
+      // Bind lines to intersects
+      pointZ.crossLines = [aBprime, bAprime];
+      pointY.crossLines = [cAprime, aCprime];
+      pointX.crossLines = [bCprime, cBprime];
+
+      const onPointMove = (e: IEvent): void => {
+        const p = e.target! as Circle;
+        // Setting the boundaries of the point's position
+        if (p.leftBound !== undefined && p.left! < p.leftBound.left!) {
+          p.left = p.leftBound.left;
+        }
+        if (p.rightBound !== undefined && p.left! > p.rightBound.left!) {
+          p.left = p.rightBound.left;
+        }
+        if (p.upLine !== undefined) {
+          p.top = 400; // Hard-coded for now
+        } else if (p.downLine !== undefined) {
+          p.top = upperLine.m! * p.left! + upperLine.b!;
+        }
 
-  function _anchorWrapper(
-    anchorIndex: number,
-    fn: (
-      eventData: MouseEvent,
-      transform: fabric.Transform,
-      x: number,
-      y: number,
-      fn2: (p: fabric.Point) => fabric.Point
-    ) => any,
-    fn2: (p: fabric.Point) => fabric.Point
-  ) {
-    return function (eventData: MouseEvent, transform: fabric.Transform, x: number, y: number) {
-      const fabricObject = transform.target as any;
-      const absolutePoint = fabric.util.transformPoint(
-        new fabric.Point(
-          fabricObject.points![anchorIndex].x - fabricObject.pathOffset.x,
-          fabricObject.points![anchorIndex].y - fabricObject.pathOffset.y
-        ),
-        fabricObject.calcTransformMatrix()
-      );
-      const actionPerformed = fn(eventData, transform, x, y, fn2);
-      const polygonBaseSize = fabricObject._getNonTransformedDimensions();
-      const newX =
-        (fabricObject.points![anchorIndex].x - fabricObject.pathOffset.x) / polygonBaseSize.x;
-      const newY =
-        (fabricObject.points![anchorIndex].y - fabricObject.pathOffset.y) / polygonBaseSize.y;
-      fabricObject.setPositionByOrigin(absolutePoint, newX + 0.5, newY + 0.5);
-      return actionPerformed;
-    };
-  }
+        if (p.upLine !== undefined) {
+          p.upLine.forEach((line) => line.set({ x1: p.left }));
+        }
+        if (p.downLine !== undefined) {
+          p.downLine.forEach((line) => line.set({ x2: p.left, y2: p.top }));
+        }
 
-  function makeMovablePolygon(
-    vertexes: fabric.Point[],
-    fn: (points: fabric.Point[]) => void,
-    fn2: (p: fabric.Point) => fabric.Point
-  ) {
-    const polygon = new fabric.Polygon(vertexes, {
-      fill: "transparent",
-      strokeWidth: 1.5,
-      stroke: "black",
-      objectCaching: false,
-      transparentCorners: false,
-      cornerStyle: "circle",
-      cornerColor: "transparent",
-      cornerSize: 20,
-      hasBorders: false,
-      lockMovementX: true,
-      lockMovementY: true,
-    });
-    polygon.controls = polygon.points!.reduce(function (acc: any, _point, index) {
-      type MyFabricControl = fabric.Control & {
-        pointIndex: number;
+        if (p.intersects !== undefined) {
+          p.intersects.forEach((inter) => {
+            const [l1, l2] = inter.crossLines!;
+            const intersect = getIntersectFromLines(l1, l2);
+            const coord = { left: intersect.x, top: intersect.y };
+            inter.set(coord);
+            if (inter.label !== undefined) {
+              setLabelToPoint([inter.label!], [coord]);
+            }
+          });
+          Object.assign(
+            collinearLine,
+            solveLinearEquation(
+              { x: collinearLine.p1!.left!, y: collinearLine.p1!.top! },
+              { x: collinearLine.p2!.left!, y: collinearLine.p2!.top! }
+            )
+          );
+          collinearLine.set({
+            x1: collinearLine.p1!.left! - COLL_OFF_SET,
+            y1: collinearLine.m! * (collinearLine.p1!.left! - COLL_OFF_SET) + collinearLine.b!,
+            x2: collinearLine.p2!.left! + COLL_OFF_SET,
+            y2: collinearLine.m! * (collinearLine.p2!.left! + COLL_OFF_SET) + collinearLine.b!,
+          });
+        }
+
+        if (p.label !== undefined) {
+          setLabelToPoint([p.label!], [{ top: p.top!, left: p.left! }]);
+        }
       };
-      const control = new fabric.Control({
-        positionHandler: _polygonPositionHandler(fn),
-        actionHandler: _anchorWrapper(
-          index > 0 ? index - 1 : polygon.points!.length - 1,
-          _actionHandler,
-          fn2
-        ),
-        actionName: "modifyPolygon",
-      }) as MyFabricControl;
-      control.pointIndex = index;
-      acc["p" + index] = control;
-      return acc;
-    }, {});
-    return polygon;
-  }
-}
 
-export default defineComponent({
-  setup() {
-    return { topic };
-  },
-  mounted() {
-    const canvas = new fabric.Canvas("Pascal-Brainchon-canvas", {
-      selection: false,
-      backgroundColor: "floralwhite",
-    });
+      canvas.on("object:moving", onPointMove);
+
+      canvas.add(
+        aLabel,
+        bLabel,
+        cLabel,
+        aprimeLabel,
+        bprimeLabel,
+        cprimeLabel,
+        xLabel,
+        yLabel,
+        zLabel
+      );
+      canvas.add(...movablePoints);
+      canvas.add(aBprime, aCprime, bAprime, bCprime, cAprime, cBprime, collinearLine);
+      canvas.add(pointX, pointY, pointZ);
+      canvas.add(bottomLine, upperLine);
+      state.firstCanvas = true;
+    }
 
-    const bottomLine = new fabric.Line([0, 400, 500, 400], { // # TODO use reduce
-      stroke: "black",
-      hasControls: false,
-      hasBorders: false,
-      evented: false,
-      strokeWidth: 2,
-    }) as Line;
-    Object.assign(
-      bottomLine,
-      solveLinearEquation(
-        new fabric.Point(bottomLine.x1!, bottomLine.y1!),
-        new fabric.Point(bottomLine.x2!, bottomLine.y2!)
-      )
-    );
-    // y = -0.12x + 100
-    const upperLine = new fabric.Line([0, 130, 500, 40], {
-      stroke: "black",
-      hasControls: false,
-      hasBorders: false,
-      evented: false,
-      strokeWidth: 2,
-    }) as Line;
-    Object.assign(
-      upperLine,
-      solveLinearEquation(
-        new fabric.Point(upperLine.x1!, upperLine.y1!),
-        new fabric.Point(upperLine.x2!, upperLine.y2!)
-      )
-    );
-
-    const aLabel = makeLabel("A", { x: -20, y: 15 });
-    const bLabel = makeLabel("B", { x: 0, y: 15 });
-    const cLabel = makeLabel("C", { x: 5, y: 15 });
-    const aprimeLabel = makeLabel("A'", { x: -20, y: -40 });
-    const bprimeLabel = makeLabel("B'", { x: 0, y: -40 });
-    const cprimeLabel = makeLabel("C'", { x: 0, y: -40 });
-    const xLabel = makeLabel("X", { x: 20, y: 0 });
-    const yLabel = makeLabel("Y", { x: -5, y: 5 });
-    const zLabel = makeLabel("Z", { x: -30, y: 0 });
-
-    // updated each point below (for Picture 1) to have radius 3, although it seems that makeCircle function already defaults radius 3 and padding 20
-    const pointA = makeCircle(50, 400, 3);
-    const pointB = makeCircle(250, 400, 3);
-    const pointC = makeCircle(450, 400, 3);
-    const pointPrimeA = makeCircle(50, upperLine.m! * 50 + upperLine.b!, 3);
-    const pointPrimeB = makeCircle(250, upperLine.m! * 250 + upperLine.b!, 3);
-    const pointPrimeC = makeCircle(450, upperLine.m! * 450 + upperLine.b!, 3);
-
-    const movablePoints = [pointA, pointB, pointC, pointPrimeA, pointPrimeB, pointPrimeC];
-
-    setLabelToPoint([aLabel, bLabel, cLabel, aprimeLabel, bprimeLabel, cprimeLabel], movablePoints);
-
-    const pointsFromMovables = movablePoints.map((ele) => new fabric.Point(ele.left!, ele.top!));
-    const [pA, pB, pC, ppA, ppB, ppC] = pointsFromMovables;
-    const aBprime = makeLine(pA, ppB, undefined, "blue");
-    const aCprime = makeLine(pA, ppC, undefined, "blue");
-    const bAprime = makeLine(pB, ppA, undefined, "blue");
-    const bCprime = makeLine(pB, ppC, undefined, "blue");
-    const cAprime = makeLine(pC, ppA, undefined, "blue");
-    const cBprime = makeLine(pC, ppB, undefined, "blue");
-
-    const pZ = fabric.Intersection.intersectLineLine(pA, ppB, ppA, pB).points![0];
-
-    const pY = (fabric.Intersection.intersectLineLine(pA, ppC, ppA, pC) as Intersection).points![0];
-    const pX = (fabric.Intersection.intersectLineLine(pB, ppC, pC, ppB) as Intersection).points![0];
-    const [pointX, pointY, pointZ] = [pX, pY, pZ].map((p) => makeCircle(p, 0.5, 0));
-    // set fill to red for points X, Y, Z
-    pointX.fill = "red";
-    pointY.fill = "red";
-    pointZ.fill = "red";
-    // Disable user dragging on intersections
-    pointX.set({ lockMovementX: true, lockMovementY: true });
-    pointY.set({ lockMovementX: true, lockMovementY: true });
-    pointZ.set({ lockMovementX: true, lockMovementY: true });
-
-    setLabelToPoint([zLabel, yLabel, xLabel], [pointZ, pointY, pointX]);
-
-    pointA.rightBound = pointB;
-    pointB.leftBound = pointA;
-    pointB.rightBound = pointC;
-    pointC.leftBound = pointB;
-    pointPrimeA.rightBound = pointPrimeB;
-    pointPrimeB.leftBound = pointPrimeA;
-    pointPrimeB.rightBound = pointPrimeC;
-    pointPrimeC.leftBound = pointPrimeB;
-
-    const COLL_OFF_SET = 100;
-    const collinearLine = makeLine(pZ, pX, 2, "red") as Line;
-    collinearLine.p1 = pointZ;
-    collinearLine.p2 = pointX;
-    Object.assign(
-      collinearLine,
-      solveLinearEquation(
-        new fabric.Point(collinearLine.p1!.left!, collinearLine.p1!.top!),
-        new fabric.Point(collinearLine.p2!.left!, collinearLine.p2!.top!)
-      )
-    );
-    collinearLine.set({
-      x1: collinearLine.p1!.left! - COLL_OFF_SET,
-      y1: collinearLine.m! * (collinearLine.p1!.left! - COLL_OFF_SET) + collinearLine.b!,
-      x2: collinearLine.p2!.left! + COLL_OFF_SET,
-      y2: collinearLine.m! * (collinearLine.p2!.left! + COLL_OFF_SET) + collinearLine.b!,
-    });
+    /**
+     * Part II
+     */
 
-    // Bind related lines and intersects to points
-    pointA.upLine = [aBprime, aCprime];
-    pointA.intersects = [pointZ, pointY];
-    pointB.upLine = [bAprime, bCprime];
-    pointB.intersects = [pointZ, pointX];
-    pointC.upLine = [cAprime, cBprime];
-    pointC.intersects = [pointY, pointX];
-    pointPrimeA.downLine = [bAprime, cAprime];
-    pointPrimeA.intersects = [pointZ, pointY];
-    pointPrimeB.downLine = [aBprime, cBprime];
-    pointPrimeB.intersects = [pointZ, pointX];
-    pointPrimeC.downLine = [aCprime, bCprime];
-    pointPrimeC.intersects = [pointY, pointX];
-
-    // Bind lines to intersects
-    pointZ.crossLines = [aBprime, bAprime];
-    pointY.crossLines = [cAprime, aCprime];
-    pointX.crossLines = [bCprime, cBprime];
-
-    const onPointMove = (e: IEvent): void => {
-      const p = e.target! as Circle;
-      // Setting the boundaries of the point's position
-      if (p.leftBound !== undefined && p.left! < p.leftBound.left!) {
-        p.left = p.leftBound.left;
+    function partTwo() {
+      if (state.secondCanvas) return;
+      const cvsPascal = new fabric.Canvas("Pascal-canvas", {
+        selection: false,
+        backgroundColor: "aliceblue",
+      });
+      const RADIUS = 80;
+      const center = { x: 150, y: 350 } as Coord;
+      let pointA = coordToPoint(polarToCartesian(RADIUS, 10, center));
+      let pointB = coordToPoint(polarToCartesian(RADIUS, 45, center));
+      let pointC = coordToPoint(polarToCartesian(RADIUS, 80, center));
+      let pointD = coordToPoint(polarToCartesian(RADIUS, 110, center));
+      let pointE = coordToPoint(polarToCartesian(RADIUS, 225, center));
+      let pointF = coordToPoint(polarToCartesian(RADIUS, 310, center));
+
+      const aLabel = makeLabel("A", { x: 5, y: -10 });
+      const bLabel = makeLabel("B", { x: -20, y: 0 });
+      const cLabel = makeLabel("C", { x: -10, y: 10 });
+      const dLabel = makeLabel("D", { x: -35, y: -20 });
+      const eLabel = makeLabel("E", { x: -10, y: 5 });
+      const fLabel = makeLabel("F", { x: 1, y: 10 });
+      setLabelToPoint(
+        [aLabel, bLabel, cLabel, dLabel, eLabel, fLabel],
+        [pointA, pointB, pointC, pointD, pointE, pointF]
+      );
+      cvsPascal.add(aLabel, bLabel, cLabel, dLabel, eLabel, fLabel);
+
+      const circle = new fabric.Circle({
+        radius: RADIUS,
+        fill: "",
+        strokeWidth: 1,
+        stroke: "black",
+        left: center.x - RADIUS,
+        top: center.y - RADIUS,
+        hasControls: false,
+        selectable: false,
+      });
+      cvsPascal.add(circle);
+
+      const xLable = makeLabel("X", { x: 0, y: -30 });
+      const yLable = makeLabel("Y", { x: -15, y: 0 });
+      const zLable = makeLabel("Z", { x: 5, y: -25 });
+      const pointX = new fabric.Point(0, 0);
+      const pointY = new fabric.Point(0, 0);
+      const pointZ = new fabric.Point(0, 0);
+      const xy = makeLine(pointX, pointY, 1, "red");
+
+      function createLine(points?: number[], color?: string, strokeWidth?: number) {
+        return new fabric.Line(points || [], {
+          originX: "center",
+          originY: "center",
+          hasControls: false,
+          hasBorders: false,
+          evented: false,
+          stroke: color || "black",
+          strokeWidth: strokeWidth || 1,
+        });
       }
-      if (p.rightBound !== undefined && p.left! > p.rightBound.left!) {
-        p.left = p.rightBound.left;
+      const dx = makeLine(pointX, pointD, 1, "blue");
+      const bx = makeLine(pointB, pointX, 1, "blue");
+      const cz = makeLine(pointC, pointZ, 1, "blue");
+      const az = makeLine(pointA, pointZ, 1, "blue");
+      const by = makeLine(pointB, pointY, 1, "blue");
+      const fy = makeLine(pointF, pointY, 1, "blue");
+
+      function circleRestrict(p: fabric.Point): fabric.Point {
+        let rad = Math.atan(-findSlope([center.x, center.y], [p.x, p.y]));
+        if (p.x < center.x) {
+          rad -= Math.PI;
+        }
+        const coord = polarToCartesian(RADIUS, rad, center, false);
+        p.setFromPoint(coord);
+        return p;
       }
-      if (p.upLine !== undefined) {
-        p.top = 400; // Hard-coded for now
-      } else if (p.downLine !== undefined) {
-        p.top = upperLine.m! * p.left! + upperLine.b!;
+
+      const pa = makeCircle(pointA);
+      const pb = makeCircle(pointB);
+      const pc = makeCircle(pointC);
+      const pd = makeCircle(pointD);
+      const pe = makeCircle(pointE);
+      const pf = makeCircle(pointF);
+      const circles = [pa, pb, pc, pd, pe, pf];
+      cvsPascal.add(pa, pb, pc, pd, pe, pf);
+
+      const poly = makeMovablePolygon(
+        [pointA, pointB, pointC, pointD, pointE, pointF],
+        function (coords: fabric.Point[]) {
+          [pointA, pointB, pointC, pointD, pointE, pointF] = coords;
+          for (let idx = 0; idx < coords.length; idx++) {
+            const c = circles[idx];
+            const coord = coords[idx];
+            c.set({ left: coord.x, top: coord.y });
+          }
+          setLabelToPoint([aLabel, bLabel, cLabel, dLabel, eLabel, fLabel], coords);
+          pointX.setFromPoint(
+            calculateLineIntersectInPoints(
+              // de - ab
+              makeLine(pointD, pointE),
+              makeLine(pointA, pointB),
+              true
+            ) as fabric.Point
+          );
+          pointY.setFromPoint(
+            calculateLineIntersectInPoints(
+              // ef - bc
+              makeLine(pointF, pointE),
+              makeLine(pointC, pointB),
+              true
+            ) as fabric.Point
+          );
+          pointZ.setFromPoint(
+            calculateLineIntersectInPoints(
+              // af - dc
+              makeLine(pointF, pointA),
+              makeLine(pointC, pointD),
+              true
+            ) as fabric.Point
+          );
+          setLabelToPoint([xLable, yLable, zLable], [pointX, pointY, pointZ]);
+          setLineFromPoints(dx, pointX, pointD);
+          setLineFromPoints(bx, pointB, pointX);
+          setLineFromPoints(cz, pointC, pointZ);
+          setLineFromPoints(az, pointA, pointZ);
+          setLineFromPoints(by, pointB, pointY);
+          setLineFromPoints(fy, pointF, pointY);
+          const { m, b } = solveLinearEquation(pointX, pointY);
+          const y1 = m * 500 + b;
+          setLineFromPoints(xy, { x: 500, y: y1 }, { x: 0, y: b });
+        },
+        circleRestrict
+      );
+      cvsPascal.add(dx, bx, cz, az, by, fy, xy);
+      cvsPascal.add(poly, xLable, yLable, zLable);
+
+      function _polygonPositionHandler(fn?: (points: fabric.Point[]) => void) {
+        return function (
+          this: { pointIndex: number },
+          _dim: any,
+          _finalMatrix: any,
+          fabricObject: fabric.Polygon
+        ) {
+          const c = fabricObject.points!.map(function (pt: fabric.Point) {
+            const transformPoint = new fabric.Point(
+              pt.x - fabricObject.pathOffset.x,
+              pt.y - fabricObject.pathOffset.y
+            );
+            return fabric.util.transformPoint(
+              transformPoint,
+              fabric.util.multiplyTransformMatrices(
+                fabricObject.canvas!.viewportTransform!,
+                fabricObject.calcTransformMatrix()
+              )
+            );
+          });
+          if (fn !== undefined) {
+            fn(c);
+          }
+          return c[this.pointIndex];
+        };
       }
 
-      if (p.upLine !== undefined) {
-        p.upLine.forEach((line) => line.set({ x1: p.left }));
+      function _actionHandler(
+        _eventData: any,
+        transform: fabric.Transform,
+        x: number,
+        y: number,
+        fn: (p: fabric.Point) => fabric.Point
+      ) {
+        type MyFabricObject = fabric.Polygon & { __corner: any };
+        const polygon = transform.target as MyFabricObject;
+        const currentControl: any = polygon.controls[polygon.__corner];
+        const mouseLocalPosition = polygon.toLocalPoint(new fabric.Point(x, y), "center", "center");
+        const polygonBaseSize = polygon._getNonTransformedDimensions();
+        const size = polygon._getTransformedDimensions(0, 0);
+        const finalPointPosition = new fabric.Point(
+          (mouseLocalPosition.x * polygonBaseSize.x) / size.x + polygon.pathOffset.x,
+          (mouseLocalPosition.y * polygonBaseSize.y) / size.y + polygon.pathOffset.y
+        );
+        polygon.points![currentControl.pointIndex] = fn(finalPointPosition);
+        return true;
       }
-      if (p.downLine !== undefined) {
-        p.downLine.forEach((line) => line.set({ x2: p.left, y2: p.top }));
+
+      function _anchorWrapper(
+        anchorIndex: number,
+        fn: (
+          eventData: MouseEvent,
+          transform: fabric.Transform,
+          x: number,
+          y: number,
+          fn2: (p: fabric.Point) => fabric.Point
+        ) => any,
+        fn2: (p: fabric.Point) => fabric.Point
+      ) {
+        return function (eventData: MouseEvent, transform: fabric.Transform, x: number, y: number) {
+          const fabricObject = transform.target as any;
+          const absolutePoint = fabric.util.transformPoint(
+            new fabric.Point(
+              fabricObject.points![anchorIndex].x - fabricObject.pathOffset.x,
+              fabricObject.points![anchorIndex].y - fabricObject.pathOffset.y
+            ),
+            fabricObject.calcTransformMatrix()
+          );
+          const actionPerformed = fn(eventData, transform, x, y, fn2);
+          const polygonBaseSize = fabricObject._getNonTransformedDimensions();
+          const newX =
+            (fabricObject.points![anchorIndex].x - fabricObject.pathOffset.x) / polygonBaseSize.x;
+          const newY =
+            (fabricObject.points![anchorIndex].y - fabricObject.pathOffset.y) / polygonBaseSize.y;
+          fabricObject.setPositionByOrigin(absolutePoint, newX + 0.5, newY + 0.5);
+          return actionPerformed;
+        };
       }
 
-      if (p.intersects !== undefined) {
-        p.intersects.forEach((inter) => {
-          const [l1, l2] = inter.crossLines!;
-          const intersect = getIntersectFromLines(l1, l2);
-          const coord = { left: intersect.x, top: intersect.y };
-          inter.set(coord);
-          if (inter.label !== undefined) {
-            setLabelToPoint([inter.label!], [coord]);
-          }
+      function makeMovablePolygon(
+        vertexes: fabric.Point[],
+        fn: (points: fabric.Point[]) => void,
+        fn2: (p: fabric.Point) => fabric.Point
+      ) {
+        const polygon = new fabric.Polygon(vertexes, {
+          fill: "transparent",
+          strokeWidth: 1.5,
+          stroke: "black",
+          objectCaching: false,
+          transparentCorners: false,
+          cornerStyle: "circle",
+          cornerColor: "transparent",
+          cornerSize: 20,
+          hasBorders: false,
+          lockMovementX: true,
+          lockMovementY: true,
         });
+        polygon.controls = polygon.points!.reduce(function (acc: any, _point, index) {
+          type MyFabricControl = fabric.Control & {
+            pointIndex: number;
+          };
+          const control = new fabric.Control({
+            positionHandler: _polygonPositionHandler(fn),
+            actionHandler: _anchorWrapper(
+              index > 0 ? index - 1 : polygon.points!.length - 1,
+              _actionHandler,
+              fn2
+            ),
+            actionName: "modifyPolygon",
+          }) as MyFabricControl;
+          control.pointIndex = index;
+          acc["p" + index] = control;
+          return acc;
+        }, {});
+        return polygon;
+      }
+      state.secondCanvas = true;
+    }
+
+    /**
+     * Part III
+     */
+    function partThree() {
+      if (state.thirdCanvas) return;
+      const cvsDes = new fabric.Canvas("Desargues-canvas", {
+        selection: false,
+        backgroundColor: "floralwhite",
+      });
+      /**
+       * Position initialization.
+       */
+      const cvsWidth = 800;
+      // (2,5.5)--(0,6)--(1.5,4)
+      const mul = 50;
+      const yOffset = 470;
+      const xOffset = 75;
+      const pointC = makeCircle(xOffset + 2 * mul, yOffset - 5.5 * mul);
+      const pointB = makeCircle(xOffset + 0 * mul, yOffset - 6 * mul);
+      const pointA = makeCircle(xOffset + 1.5 * mul, yOffset - 4 * mul);
+      // (5.5,1.125)--(0,0)--(2.25,2)
+      const pointPrimeC = makeCircle(xOffset + mul * 5.5, yOffset - mul * 1.125, 1, undefined);
+      const pointPrimeB = makeCircle(xOffset + mul * 0, yOffset - mul * 0, 1, undefined);
+      const pointPrimeA = makeCircle(xOffset + mul * 2.25, yOffset - mul * 2, 1, undefined);
+      const abc = new fabric.Polygon(circleToCoord(pointA, pointB, pointC), { fill: "yellow" });
+      const primeTriangle = new fabric.Polygon(
+        circleToCoord(pointPrimeA, pointPrimeB, pointPrimeC),
+        {
+          fill: "#5efc03",
+        }
+      );
+      abc.selectable = false;
+      abc.evented = false;
+      primeTriangle.selectable = false;
+      primeTriangle.evented = false;
+      cvsDes.add(abc, primeTriangle);
+      cvsDes.add(pointA, pointB, pointC, pointPrimeA, pointPrimeB, pointPrimeC);
+
+      const aLabel = makeLabel("A", { x: 15, y: -10 });
+      const bLabel = makeLabel("B", { x: -18, y: 5 });
+      const cLabel = makeLabel("C", { x: 15, y: -20 });
+      const aprimeLabel = makeLabel("A'", { x: -10, y: 5 });
+      const bprimeLabel = makeLabel("B'");
+      const cprimeLabel = makeLabel("C'");
+      const movablePoints = [pointA, pointB, pointC, pointPrimeA, pointPrimeB, pointPrimeC];
+      setLabelToPoint(
+        [aLabel, bLabel, cLabel, aprimeLabel, bprimeLabel, cprimeLabel],
+        movablePoints
+      );
+      // const pointsFromMovables = movablePoints.map(ele => new fabric.Point(ele.left!, ele.top!));
+      // const [pa, pb, pc, ppa, ppb, ppc] = pointsFromMovables;
+      cvsDes.add(aLabel, bLabel, cLabel, aprimeLabel, bprimeLabel, cprimeLabel);
+
+      const aAprime = makeLine(pointA, pointPrimeA);
+      const bBprime = makeLine(pointB, pointPrimeB);
+      // const cCprime = makeLine(pointC, pointPrimeC);
+      // cvsDes.add(aAprime, bBprime, cCprime);
+      const pO = calculateLineIntersectInPoints(aAprime, bBprime, true);
+      const pointO = makeCircle(pO!, 0.5);
+      const oBp = makeLine(pointO, pointPrimeB);
+      const oCp = makeLine(pointO, pointPrimeC);
+      const oAp = makeLine(pointO, pointPrimeA);
+      pointB.moveLine = oBp;
+      pointA.moveLine = oAp;
+      pointC.moveLine = oCp;
+      pointA.upBound = pointPrimeA;
+      pointA.downBound = pointO;
+      pointB.upBound = pointPrimeB;
+      pointB.downBound = pointO;
+      pointC.upBound = pointPrimeC;
+      pointC.downBound = pointO;
+      Object.assign(
+        oAp,
+        solveLinearEquation(
+          { x: pointO.left!, y: pointO.top! },
+          { x: pointPrimeA.left!, y: pointPrimeA.top! }
+        )
+      );
+      Object.assign(
+        oBp,
+        solveLinearEquation(
+          { x: pointO.left!, y: pointO.top! },
+          { x: pointPrimeB.left!, y: pointPrimeB.top! }
+        )
+      );
+      Object.assign(
+        oCp,
+        solveLinearEquation(
+          { x: pointO.left!, y: pointO.top! },
+          { x: pointPrimeC.left!, y: pointPrimeC.top! }
+        )
+      );
+      cvsDes.add(pointO, oBp, oCp, oAp);
+      // Triangle part
+      const ab = makeLine(pointA, pointB);
+      const ac = makeLine(pointA, pointC);
+      const bc = makeLine(pointB, pointC);
+      const apBp = makeLine(pointPrimeA, pointPrimeB);
+      const apCp = makeLine(pointPrimeA, pointPrimeC);
+      const bpCp = makeLine(pointPrimeB, pointPrimeC);
+      cvsDes.add(ab, ac, bc, apBp, apCp, bpCp);
+      // Assign respective lines and points
+      Object.assign(ab, {
+        p1: pointA,
+        p2: pointB,
+        thatLine: apBp,
+      });
+      Object.assign(ac, {
+        p1: pointA,
+        p2: pointC,
+        thatLine: apCp,
+      });
+      Object.assign(bc, {
+        p1: pointC,
+        p2: pointB,
+        thatLine: bpCp,
+      });
+      Object.assign(apBp, {
+        p1: pointPrimeA,
+        p2: pointPrimeB,
+        thatLine: ab,
+      });
+      Object.assign(apCp, {
+        p1: pointPrimeA,
+        p2: pointPrimeC,
+        thatLine: ac,
+      });
+      Object.assign(bpCp, {
+        p1: pointPrimeC,
+        p2: pointPrimeB,
+        thatLine: bc,
+      });
+      pointA.crossLines = [ab, ac];
+      pointB.crossLines = [ab, bc];
+      pointC.crossLines = [ac, bc];
+
+      // Collinear & cocurrent
+      const pointP = makeCircle(calculateLineIntersectInPoints(bc, bpCp, true)!, 0.5);
+      const cp = makeLine(pointC, pointP);
+      const cpP = makeLine(pointPrimeC, pointP);
+
+      const pointQ = makeCircle(calculateLineIntersectInPoints(ac, apCp, true)!, 0.5);
+      const pointR = makeCircle(calculateLineIntersectInPoints(ab, apBp, true)!, 0.5);
+      const aq = makeLine(pointA, pointQ);
+      const apQ = makeLine(pointPrimeA, pointQ);
+      const ar = makeLine(pointA, pointR);
+      const apR = makeLine(pointPrimeA, pointR);
+      const pq = makeLine(pointP, pointQ);
+      pq.p1 = pointP;
+      pq.p2 = pointQ;
+      cvsDes.add(cp, cpP, aq, apQ, ar, apR, pq);
+      cvsDes.add(pointP, pointQ, pointR);
+      // Assigning intersections
+      ab.inter = pointR;
+      apBp.inter = pointR;
+      ac.inter = pointQ;
+      apCp.inter = pointQ;
+      bc.inter = pointP;
+      bpCp.inter = pointP;
+      // Intersection lines
+      pointR.crossLines = [ar, apR];
+      ar.p1 = pointA;
+      ar.p2 = pointR;
+      apR.p1 = pointPrimeA;
+      apR.p2 = pointR;
+      pointQ.crossLines = [aq, apQ];
+      aq.p1 = pointQ;
+      aq.p2 = pointA;
+      apQ.p1 = pointPrimeA;
+      apQ.p2 = pointQ;
+      pointP.crossLines = [cp, cpP];
+      cp.p1 = pointC;
+      cp.p2 = pointP;
+      cpP.p1 = pointPrimeC;
+      cpP.p2 = pointP;
+      const oLabel = makeLabel("O", { x: -5, y: -30 });
+      const pLabel = makeLabel("P");
+      const qLabel = makeLabel("Q", { x: -25, y: 0 });
+      const rLabel = makeLabel("R", { x: 10, y: 0 });
+      setLabelToPoint([oLabel, pLabel, qLabel, rLabel], [pointO, pointP, pointQ, pointR]);
+      cvsDes.add(oLabel, pLabel, qLabel, rLabel);
+      [pointPrimeA, pointPrimeB, pointPrimeC, pointO, pointP, pointQ, pointR].forEach((p) => {
+        p.set({ lockMovementX: true, lockMovementY: true, evented: false });
+      });
+
+      // Interaction
+      const onPointMove = (e: IEvent): void => {
+        const p = e.target! as Circle;
+        // Restrict movement to line
+        if (p.moveLine !== undefined) {
+          // Restric boundries
+          if (p.upBound !== undefined && p.top! > p.upBound.top!) p.top = p.upBound.top;
+          if (p.downBound !== undefined && p.top! < p.downBound.top!) p.top = p.downBound.top;
+          let x = (p.top! - p.moveLine.b!) / p.moveLine.m!;
+          if (p.moveLine.m === Infinity) x = p.moveLine.x1!;
+          p.set("left", x);
+        }
+        abc.set("points", circleToCoord(pointA, pointB, pointC));
+
+        if (p.crossLines !== undefined) {
+          p.crossLines.forEach((line) => {
+            // Adjust line position
+            line.set({
+              x1: line.p1!.left,
+              y1: line.p1!.top,
+              x2: line.p2!.left,
+              y2: line.p2!.top,
+            });
+            // Adjust intersections accordingly
+            if (line.inter !== undefined && line.inter.crossLines !== undefined) {
+              updateInterAndLine(line, line.thatLine!, line.inter);
+              setLabelToPoint([line.inter.label!], [line.inter]);
+            }
+          });
+        }
+        // Update the collinear PQ line
+        // Extend to canvas width
         Object.assign(
-          collinearLine,
+          pq,
           solveLinearEquation(
-            { x: collinearLine.p1!.left!, y: collinearLine.p1!.top! },
-            { x: collinearLine.p2!.left!, y: collinearLine.p2!.top! }
+            { x: pq.p1!.left!, y: pq.p1!.top! },
+            { x: pq.p2!.left!, y: pq.p2!.top! }
           )
         );
-        collinearLine.set({
-          x1: collinearLine.p1!.left! - COLL_OFF_SET,
-          y1: collinearLine.m! * (collinearLine.p1!.left! - COLL_OFF_SET) + collinearLine.b!,
-          x2: collinearLine.p2!.left! + COLL_OFF_SET,
-          y2: collinearLine.m! * (collinearLine.p2!.left! + COLL_OFF_SET) + collinearLine.b!,
+        pq.set({
+          x1: 0,
+          y1: pq.b,
+          x2: cvsWidth,
+          y2: cvsWidth * pq.m! + pq.b!,
         });
-      }
+        // Update according to position change
+        if (p.label !== undefined) {
+          setLabelToPoint([p.label], [p]);
+        }
+      };
+      cvsDes.on("object:moving", onPointMove);
+      state.thirdCanvas = true;
+    }
 
-      if (p.label !== undefined) {
-        setLabelToPoint([p.label!], [{ top: p.top!, left: p.left! }]);
+    /**
+     * Part IV
+     */
+    function partFour() {
+      if (state.fouthCanvas) {
+        return;
       }
-    };
+      const cvsBra = new fabric.Canvas("Brainchon-canvas", {
+        selection: false,
+        backgroundColor: "floralwhite",
+      });
+      const RADIUS = 120;
+      const center = { x: 250, y: 250 } as Coord;
+      const centerPoint = makeCircle(center);
+      centerPoint.evented = false;
+
+      const circle = new fabric.Circle({
+        radius: RADIUS,
+        fill: "",
+        strokeWidth: 1,
+        stroke: "black",
+        left: center.x - RADIUS,
+        top: center.y - RADIUS,
+        hasControls: false,
+        selectable: false,
+        evented: false,
+      });
+      cvsBra.add(circle);
+
+      const taf = coordToPoint(polarToCartesian(RADIUS, 30, center));
+      const tab = coordToPoint(polarToCartesian(RADIUS, 80, center));
+      const tbc = coordToPoint(polarToCartesian(RADIUS, 120, center));
+      const tcd = coordToPoint(polarToCartesian(RADIUS, 2000, center));
+      const tde = coordToPoint(polarToCartesian(RADIUS, 280, center));
+      const tef = coordToPoint(polarToCartesian(RADIUS, -20, center));
+
+      const abLinear = getTangentLine(tab, RADIUS, center);
+      const bcLinear = getTangentLine(tbc, RADIUS, center);
+      const cdLinear = getTangentLine(tcd, RADIUS, center);
+      const deLinear = getTangentLine(tde, RADIUS, center);
+      const efLinear = getTangentLine(tef, RADIUS, center);
+      const faLinear = getTangentLine(taf, RADIUS, center);
+
+      const pa = makeCircle(getInterByLinearEq(abLinear, faLinear));
+      const pb = makeCircle(getInterByLinearEq(abLinear, bcLinear));
+      const pc = makeCircle(getInterByLinearEq(bcLinear, cdLinear));
+      const pd = makeCircle(getInterByLinearEq(cdLinear, deLinear));
+      const pe = makeCircle(getInterByLinearEq(deLinear, efLinear));
+      const pf = makeCircle(getInterByLinearEq(efLinear, faLinear));
+
+      const ab = makeLine(pa, pb);
+      const bc = makeLine(pb, pc);
+      const cd = makeLine(pd, pc);
+      const de = makeLine(pd, pe);
+      const ef = makeLine(pf, pe);
+      const fa = makeLine(pf, pa);
+
+      ab.tan = makeCircle(
+        new fabric.Point(pa.left!, pa.top!).lerp({ x: pb.left!, y: pb.top! }, 0.5)
+      );
+      bc.tan = makeCircle(
+        new fabric.Point(pc.left!, pc.top!).lerp({ x: pb.left!, y: pb.top! }, 0.5)
+      );
+      cd.tan = makeCircle(
+        new fabric.Point(pc.left!, pc.top!).lerp({ x: pd.left!, y: pd.top! }, 0.5)
+      );
+      de.tan = makeCircle(
+        new fabric.Point(pd.left!, pd.top!).lerp({ x: pe.left!, y: pe.top! }, 0.5)
+      );
+      ef.tan = makeCircle(
+        new fabric.Point(pe.left!, pe.top!).lerp({ x: pf.left!, y: pf.top! }, 0.5)
+      );
+      fa.tan = makeCircle(
+        new fabric.Point(pa.left!, pa.top!).lerp({ x: pf.left!, y: pf.top! }, 0.5)
+      );
+      // Tangent lines
+      ab.tan.clockLine = makeLine(ab.tan, pa);
+      ab.tan.cntClockLine = makeLine(ab.tan, pb);
+      bc.tan.clockLine = makeLine(bc.tan, pb);
+      bc.tan.cntClockLine = makeLine(bc.tan, pc);
+      cd.tan.clockLine = makeLine(cd.tan, pc);
+      cd.tan.cntClockLine = makeLine(cd.tan, pd);
+      de.tan.clockLine = makeLine(de.tan, pd);
+      de.tan.cntClockLine = makeLine(de.tan, pe);
+      ef.tan.clockLine = makeLine(ef.tan, pe);
+      ef.tan.cntClockLine = makeLine(ef.tan, pf);
+      fa.tan.clockLine = makeLine(fa.tan, pf);
+      fa.tan.cntClockLine = makeLine(fa.tan, pa);
+      ab.tan.clockLine.set({ x1: 0, y1: 0, x2: 0, y2: 0 });
+      bc.tan.clockLine.set({ x1: 0, y1: 0, x2: 0, y2: 0 });
+      cd.tan.clockLine.set({ x1: 0, y1: 0, x2: 0, y2: 0 });
+      de.tan.clockLine.set({ x1: 0, y1: 0, x2: 0, y2: 0 });
+      ef.tan.clockLine.set({ x1: 0, y1: 0, x2: 0, y2: 0 });
+      fa.tan.clockLine.set({ x1: 0, y1: 0, x2: 0, y2: 0 });
+      [ab, bc, cd, de, ef, fa].forEach((line) => {
+        if (line.tan !== undefined) {
+          line.tan.clockLine?.set({ strokeDashArray: [10], stroke: "Aqua" });
+          line.tan.cntClockLine?.set({ strokeDashArray: [10], stroke: "Aqua" });
+          // line.tan.clockLine?.set({x1: 0, y1: 0, x2: 0, y2: 0});
+          // line.tan.cntClockLine?.set({x1: 0, y1: 0, x2: 0, y2: 0});
+          cvsBra.add(line.tan.clockLine!, line.tan.cntClockLine!);
+        }
+      });
 
-    canvas.on("object:moving", onPointMove);
-
-    canvas.add(
-      aLabel,
-      bLabel,
-      cLabel,
-      aprimeLabel,
-      bprimeLabel,
-      cprimeLabel,
-      xLabel,
-      yLabel,
-      zLabel
-    );
-    canvas.add(...movablePoints);
-    canvas.add(aBprime, aCprime, bAprime, bCprime, cAprime, cBprime, collinearLine);
-    canvas.add(pointX, pointY, pointZ);
-    canvas.add(bottomLine, upperLine);
+      const ad = makeLine(pa, pd, undefined, "green");
+      const be = makeLine(pb, pe, undefined, "green");
+      const cf = makeLine(pc, pf, undefined, "green");
+      Object.assign(ad, solveLinearEquation({ x: ad.x1!, y: ad.y1! }, { x: ad.x2!, y: ad.y2! }));
+      Object.assign(be, solveLinearEquation({ x: be.x1!, y: be.y1! }, { x: be.x2!, y: be.y2! }));
+      const intersection = makeCircle(
+        getInterByLinearEq({ m: ad.m!, b: ad.b! }, { m: be.m!, b: be.b! }),
+        3,
+        "red"
+      );
+      intersection.set({ selectable: false, evented: false });
+      const ia = makeLine(intersection, pa, undefined, "green");
+      const ib = makeLine(intersection, pb, undefined, "green");
+      const ic = makeLine(intersection, pc, undefined, "green");
+      const id = makeLine(intersection, pd, undefined, "green");
+      const ie = makeLine(intersection, pe, undefined, "green");
+      const iF = makeLine(intersection, pf, undefined, "green");
+
+      pa.clockLine = fa;
+      pa.cntClockLine = ab;
+      pb.clockLine = ab;
+      pb.cntClockLine = bc;
+      pc.clockLine = bc;
+      pc.cntClockLine = cd;
+      pd.clockLine = cd;
+      pd.cntClockLine = de;
+      pe.clockLine = de;
+      pe.cntClockLine = ef;
+      pf.clockLine = ef;
+      pf.cntClockLine = fa;
+
+      pa.clockPoint = pf;
+      pa.cntClockPoint = pb;
+      pb.clockPoint = pa;
+      pb.cntClockPoint = pc;
+      pc.clockPoint = pb;
+      pc.cntClockPoint = pd;
+      pd.clockPoint = pc;
+      pd.cntClockPoint = pe;
+      pe.clockPoint = pd;
+      pe.cntClockPoint = pf;
+      pf.clockPoint = pe;
+      pf.cntClockPoint = pa;
+
+      ab.p1 = pa;
+      ab.p2 = pb;
+      bc.p1 = pb;
+      bc.p2 = pc;
+      cd.p1 = pc;
+      cd.p2 = pd;
+      de.p1 = pd;
+      de.p2 = pe;
+      ef.p1 = pe;
+      ef.p2 = pf;
+      fa.p1 = pa;
+      fa.p2 = pf;
+      ad.p1 = pa;
+      ad.p2 = pd;
+      be.p1 = pb;
+      be.p2 = pe;
+      cf.p1 = pc;
+      cf.p2 = pf;
+      ia.p1 = pa;
+      ib.p1 = pb;
+      ic.p1 = pc;
+      id.p1 = pd;
+      ie.p1 = pe;
+      iF.p1 = pf;
+
+      const aLabel = makeLabel("A", { x: 10, y: -20 });
+      const bLabel = makeLabel("B", { x: 0, y: -30 });
+      const cLabel = makeLabel("C", { x: -25, y: -5 });
+      const dLabel = makeLabel("D", { x: -5, y: 10 });
+      const eLabel = makeLabel("E");
+      const fLabel = makeLabel("F");
+      const oLabel = makeLabel("O");
+      setLabelToPoint(
+        [aLabel, bLabel, cLabel, dLabel, eLabel, fLabel, oLabel],
+        [pa, pb, pc, pd, pe, pf, centerPoint]
+      );
+      cvsBra.add(aLabel, bLabel, cLabel, dLabel, eLabel, fLabel, oLabel);
+      cvsBra.add(pa, pb, pc, pd, pe, pf, centerPoint);
+      cvsBra.add(ia, ib, ic, id, ie, iF);
+      cvsBra.add(intersection);
+      cvsBra.add(ab, bc, cd, de, ef, fa);
+
+      const onPointMove = (e: IEvent): void => {
+        const p = e.target! as Circle;
+        let dist = calculateDistanceBetweenTwoPoints(circleToCoord(p)[0], center);
+        const offset = 10;
+        if (dist <= RADIUS + offset) {
+          dist = RADIUS + offset;
+        }
+        const alpha = Math.acos(RADIUS / dist);
+        let rad = Math.atan(-findSlope([center.x, center.y], [p.left!, p.top!]));
 
-    /**
-     * Part two of animation Pascal Theorem
-     */
-    partTwo();
+        if (p.left! < center.x) {
+          rad -= Math.PI;
+        }
+        // Restrict movement outside of circle.
+        if (dist <= RADIUS + offset) {
+          const onCircle = polarToCartesian(RADIUS + offset, rad, center, false);
+          p.set({ left: onCircle.x, top: onCircle.y });
+        }
+        setLabelToPoint([p.label!], [p]);
+        const clkRad = rad - alpha;
+        const cntClkRad = alpha + rad;
+        // New tangent point and lines
+        const clkT = polarToCartesian(RADIUS, clkRad, center, false);
+        const cntClkT = polarToCartesian(RADIUS, cntClkRad, center, false);
+        // Update closest tangent points.
+        p.clockLine!.tan!.set({ left: clkT.x, top: clkT.y });
+        p.cntClockLine!.tan!.set({ left: cntClkT.x, top: cntClkT.y });
+        const clkLinearEq = solveLinearEquation(circleToCoord(p)[0], clkT);
+        const cntClkLinearEq = solveLinearEquation(circleToCoord(p)[0], cntClkT);
+
+        // New intersections
+        let clkLine = p.clockPoint!.clockLine!;
+        let cntClkLine = p.cntClockPoint!.cntClockLine!;
+        const clkP = getInterByLinearEq(
+          clkLinearEq,
+          solveLinearEquation(
+            { x: clkLine.x1!, y: clkLine.y1! },
+            { x: clkLine.x2!, y: clkLine.y2! }
+          )
+        );
+        p.clockPoint!.set({ left: clkP.x, top: clkP.y });
+        const cntClkP = getInterByLinearEq(
+          cntClkLinearEq,
+          solveLinearEquation(
+            { x: cntClkLine.x1!, y: cntClkLine.y1! },
+            { x: cntClkLine.x2!, y: cntClkLine.y2! }
+          )
+        );
+        p.cntClockPoint!.set({ left: cntClkP.x, top: cntClkP.y });
 
-    /**
-     * Part three of animation: Desargues' Theorem
-     */
-    partThree();
+        // Update lines accordingly
+        setLineFromPoints(
+          clkLine,
+          { x: clkLine.p1!.left!, y: clkLine.p1!.top! },
+          { x: clkLine.p2!.left!, y: clkLine.p2!.top! }
+        );
+        setLineFromPoints(
+          cntClkLine,
+          { x: cntClkLine.p1!.left!, y: cntClkLine.p1!.top! },
+          { x: cntClkLine.p2!.left!, y: cntClkLine.p2!.top! }
+        );
+        // clkLine.tan!.set();
+        // Update strokes
+        [clkLine, cntClkLine].forEach((line) => {
+          if (
+            line.tan !== undefined &&
+            line.tan.clockLine !== undefined &&
+            line.tan.cntClockLine !== undefined
+          ) {
+            setLineFromPoints(
+              line.tan.clockLine,
+              { x: line.tan.clockLine.p1!.left!, y: line.tan.clockLine.p1!.top! },
+              { x: line.tan.clockLine.p2!.left!, y: line.tan.clockLine.p2!.top! }
+            );
+            setLineFromPoints(
+              line.tan.cntClockLine,
+              { x: line.tan.cntClockLine.p1!.left!, y: line.tan.cntClockLine.p1!.top! },
+              { x: line.tan.cntClockLine.p2!.left!, y: line.tan.cntClockLine.p2!.top! }
+            );
+          }
+        });
 
-    /**
-     * Part IV
-     */
-    partFour();
+        clkLine = p.clockLine!;
+        setLineFromPoints(
+          clkLine,
+          { x: clkLine.p1!.left!, y: clkLine.p1!.top! },
+          { x: clkLine.p2!.left!, y: clkLine.p2!.top! }
+        );
+        cntClkLine = p.cntClockLine!;
+        setLineFromPoints(
+          cntClkLine,
+          { x: cntClkLine.p1!.left!, y: cntClkLine.p1!.top! },
+          { x: cntClkLine.p2!.left!, y: cntClkLine.p2!.top! }
+        );
+        // Update intersections
+        [ad, be].forEach((line) => {
+          setLineFromPoints(
+            line,
+            { x: line.p1!.left!, y: line.p1!.top! },
+            { x: line.p2!.left!, y: line.p2!.top! }
+          );
+        });
+        [clkLine, cntClkLine].forEach((line) => {
+          if (
+            line.tan !== undefined &&
+            line.tan.clockLine !== undefined &&
+            line.tan.cntClockLine !== undefined
+          ) {
+            setLineFromPoints(
+              line.tan.clockLine,
+              { x: line.tan.clockLine.p1!.left!, y: line.tan.clockLine.p1!.top! },
+              { x: line.tan.clockLine.p2!.left!, y: line.tan.clockLine.p2!.top! }
+            );
+            setLineFromPoints(
+              line.tan.cntClockLine,
+              { x: line.tan.cntClockLine.p1!.left!, y: line.tan.cntClockLine.p1!.top! },
+              { x: line.tan.cntClockLine.p2!.left!, y: line.tan.cntClockLine.p2!.top! }
+            );
+          }
+        });
+
+        Object.assign(ad, solveLinearEquation({ x: ad.x1!, y: ad.y1! }, { x: ad.x2!, y: ad.y2! }));
+        Object.assign(be, solveLinearEquation({ x: be.x1!, y: be.y1! }, { x: be.x2!, y: be.y2! }));
+        const updateInter = getInterByLinearEq({ m: ad.m!, b: ad.b! }, { m: be.m!, b: be.b! });
+        intersection.set({ left: updateInter.x, top: updateInter.y });
+        [ia, ib, ic, id, ie, iF].forEach((line) =>
+          setLineFromPoints(
+            line,
+            { x: line.p1!.left!, y: line.p1!.top! },
+            { x: intersection.left!, y: intersection.top! }
+          )
+        );
+
+        setLabelToPoint(
+          [p.clockPoint!.label!, p.cntClockPoint!.label!],
+          [p.clockPoint!, p.cntClockPoint!]
+        );
+      };
+
+      cvsBra.on("object:moving", onPointMove);
+      state.fouthCanvas = true;
+    }
+
+    onMounted(() => {
+      handleTabChange(state.activeKey1);
+    });
+
+    return {
+      ...toRefs(state),
+      handleTabChange,
+    };
   },
 });