diff --git a/aoc_2023/day_18/__init__.py b/aoc_2023/day_18/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/aoc_2023/day_18/a.py b/aoc_2023/day_18/a.py
new file mode 100644
index 0000000..67cf186
--- /dev/null
+++ b/aoc_2023/day_18/a.py
@@ -0,0 +1,34 @@
+from dataclasses import dataclass
+from functools import cached_property
+from aoc_2023.day_18.common import Instruction, Solver
+from aoc_2023.day_18.parser import Parser
+
+
+@dataclass
+class Day18PartASolver:
+    instructions: list[Instruction]
+
+    @property
+    def solution(self) -> int:
+        return Solver(self.instructions).solution
+
+    @cached_property
+    def solver(self) -> Solver:
+        return Solver(self.instructions)
+
+
+def solve(input: str) -> int:
+    data = Parser.parse(input)
+    solver = Day18PartASolver(data)
+
+    return solver.solution
+
+
+def get_solution() -> int:
+    with open("aoc_2023/day_18/input.txt", "r") as f:
+        input = f.read()
+    return solve(input)
+
+
+if __name__ == "__main__":
+    print(get_solution())
diff --git a/aoc_2023/day_18/b.py b/aoc_2023/day_18/b.py
new file mode 100644
index 0000000..f308f2a
--- /dev/null
+++ b/aoc_2023/day_18/b.py
@@ -0,0 +1,54 @@
+from dataclasses import dataclass
+from functools import cached_property
+from aoc_2023.day_18.common import (
+    Instruction,
+    Solver,
+)
+from aoc_2023.day_18.parser import Parser
+
+
+@dataclass
+class Day18PartBSolver:
+    wrong_instructions: list[Instruction]
+
+    @property
+    def solution(self) -> int:
+        return Solver(self.instructions).solution
+
+    @cached_property
+    def solver(self) -> Solver:
+        return Solver(self.instructions)
+
+    @cached_property
+    def instructions(self) -> list[Instruction]:
+        return [self.correct_instruction(inst) for inst in self.wrong_instructions]
+
+    def correct_instruction(self, instruction: Instruction) -> Instruction:
+        dist = instruction.color[:5]
+        direction = instruction.color[-1]
+
+        DIRECTION_MAP = {
+            "0": "R",
+            "1": "D",
+            "2": "L",
+            "3": "U",
+        }
+
+        return Instruction(DIRECTION_MAP[direction], int(dist, 16), instruction.color)
+
+
+def solve(input: str) -> int:
+    data = Parser.parse(input)
+    solver = Day18PartBSolver(data)
+
+    return solver.solution
+
+
+def get_solution() -> int:
+    with open("aoc_2023/day_18/input.txt", "r") as f:
+        input = f.read()
+    return solve(input)
+
+
+if __name__ == "__main__":
+    print(get_solution())
diff --git a/aoc_2023/day_18/common.py b/aoc_2023/day_18/common.py
new file mode 100644
index 0000000..d41d9ed
--- /dev/null
+++ b/aoc_2023/day_18/common.py
@@ -0,0 +1,143 @@
+from __future__ import annotations
+from dataclasses import dataclass
+from functools import cached_property
+
+from aoc_2023.tools.point import Point
+
+
+@dataclass
+class Instruction:
+    direction: str
+    length: int
+    color: str
+
+
+@dataclass(frozen=True)
+class VerticalSegment:
+    x: int
+    y_range: tuple[int, int]
+
+    def __post_init__(self):
+        assert self.y_range[0] < self.y_range[1]
+
+
+UP = Point(0, -1)
+DOWN = Point(0, 1)
+LEFT = Point(-1, 0)
+RIGHT = Point(1, 0)
+
+INSTRUCTION_MAP = {
+    "U": UP,
+    "D": DOWN,
+    "L": LEFT,
+    "R": RIGHT,
+}
+
+
+@dataclass
+class Solver:
+    instructions: list[Instruction]
+
+    @cached_property
+    def solution(self) -> int:
+        by_y = self.segments_by_y_range
+        terminals = set[VerticalSegment]()
+        output = 0
+
+        for x in self.xs:
+            for segment in self.segments_by_x[x]:
+                if segment not in terminals:
+                    index_by_y = by_y[segment.y_range].index(segment)
+                    end_segment = by_y[segment.y_range][index_by_y + 1]
+                    width = (end_segment.x + 1) - segment.x
+                    assert width > 0
+                    height = segment.y_range[1] - segment.y_range[0]
+                    assert height > 0
+                    output += width * height
+                    terminals.add(end_segment)
+
+        output += self.left_len
+        output += 1
+        return output
+
+    @cached_property
+    def xs(self) -> list[int]:
+        return sorted({p.x for p in self.points})
+
+    @cached_property
+    def ys(self) -> list[int]:
+        return sorted({p.y for p in self.points})
+
+    @cached_property
+    def points(self) -> list[Point]:
+        pos = Point(0, 0)
+        output = [pos]
+        for inst in self.instructions:
+            move = INSTRUCTION_MAP[inst.direction].multiply(inst.length)
+            pos = pos.add(move)
+            output.append(pos)
+        return output
+
+    @cached_property
+    def segments_by_x(self) -> dict[int, list[VerticalSegment]]:
+        output = dict[int, list[VerticalSegment]]()
+        for segment in self.small_vertical_segments:
+            if segment.x not in output:
+                output[segment.x] = []
+            output[segment.x].append(segment)
+        for segments in output.values():
+            segments.sort(key=lambda s: s.y_range)
+        return output
+
+    @cached_property
+    def segments_by_y_range(self) -> dict[tuple[int, int], list[VerticalSegment]]:
+        output = dict[tuple[int, int], list[VerticalSegment]]()
+        for segment in self.small_vertical_segments:
+            if segment.y_range not in output:
+                output[segment.y_range] = []
+            output[segment.y_range].append(segment)
+        for segments in output.values():
+            segments.sort(key=lambda s: s.x)
+        return output
+
+    @cached_property
+    def small_vertical_segments(self) -> list[VerticalSegment]:
+        output = list[VerticalSegment]()
+        for large_segment in self.large_vertical_segments:
+            ys = [
+                y
+                for y in self.ys
+                if y >= large_segment.y_range[0] and y <= large_segment.y_range[1]
+            ]
+            for i in range(1, len(ys)):
+                output.append(
+                    VerticalSegment(
+                        x=large_segment.x,
+                        y_range=(ys[i - 1], ys[i]),
+                    )
+                )
+
+        return output
+
+    @cached_property
+    def large_vertical_segments(self) -> list[VerticalSegment]:
+        pos = Point(0, 0)
+        output = list[VerticalSegment]()
+        for inst in self.instructions:
+            move = INSTRUCTION_MAP[inst.direction].multiply(inst.length)
+            new_pos = pos.add(move)
+            if new_pos.x == pos.x:
+                output.append(
+                    VerticalSegment(
+                        x=new_pos.x,
+                        y_range=(pos.y, new_pos.y)
+                        if pos.y < new_pos.y
+                        else (new_pos.y, pos.y),
+                    )
+                )
+            pos = new_pos
+        return output
+
+    @cached_property
+    def left_len(self) -> int:
+        return sum(inst.length for inst in self.instructions if inst.direction == "L")
diff --git a/aoc_2023/day_18/from_prompt.py b/aoc_2023/day_18/from_prompt.py
new file mode 100644
index 0000000..fb89c5c
Binary files /dev/null and b/aoc_2023/day_18/from_prompt.py differ
diff --git a/aoc_2023/day_18/input.txt b/aoc_2023/day_18/input.txt
new file mode 100644
index 0000000..6be505b
Binary files /dev/null and b/aoc_2023/day_18/input.txt differ
diff --git a/aoc_2023/day_18/parser.py b/aoc_2023/day_18/parser.py
new file mode 100644
index 0000000..65caad8
--- /dev/null
+++ b/aoc_2023/day_18/parser.py
@@ -0,0 +1,14 @@
+from aoc_2023.day_18.common import Instruction
+
+
+class Parser:
+    @staticmethod
+    def parse(input: str) -> list[Instruction]:
+        lines = input.strip().splitlines()
+        return [Parser.parse_line(line) for line in lines]
+
+    @staticmethod
+    def parse_line(line: str) -> Instruction:
+        direction, length, color = line.split()
+
+        return Instruction(direction, int(length), color[2:-1])
diff --git a/tests/test_day_18/__init__.py b/tests/test_day_18/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/test_day_18/test_a.py b/tests/test_day_18/test_a.py
new file mode 100644
index 0000000..47a6ce9
--- /dev/null
+++ b/tests/test_day_18/test_a.py
@@ -0,0 +1,10 @@
+from aoc_2023.day_18.a import get_solution, solve
+from aoc_2023.day_18.from_prompt import SAMPLE_DATA, SAMPLE_SOLUTION_A
+
+
+def test_solve():
+    assert solve(SAMPLE_DATA) == SAMPLE_SOLUTION_A
+
+
+def test_my_solution():
+    assert get_solution() == 40714
diff --git a/tests/test_day_18/test_b.py b/tests/test_day_18/test_b.py
new file mode 100644
index 0000000..b18cc46
--- /dev/null
+++ b/tests/test_day_18/test_b.py
@@ -0,0 +1,10 @@
+from aoc_2023.day_18.b import get_solution, solve
+from aoc_2023.day_18.from_prompt import SAMPLE_DATA, SAMPLE_SOLUTION_B
+
+
+def test_solve():
+    assert solve(SAMPLE_DATA) == SAMPLE_SOLUTION_B
+
+
+def test_my_solution():
+    assert get_solution() == 129849166997110