diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..4231d4d
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,29 @@
+name: CI
+
+on: [push]
+
+jobs:
+  test:
+    name: ${{ matrix.lisp }} on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        lisp: [sbcl-bin]
+        os: [ubuntu-latest] # , macOS-latest
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Install SDL2
+        run: |
+          sudo apt install libsdl2-dev libsdl2-image-dev libsdl2-ttf-dev
+
+      - name: Install Roswell
+        env:
+          LISP: ${{ matrix.lisp }}
+        run: |
+          curl -L https://raw.githubusercontent.com/roswell/roswell/master/scripts/install-for-ci.sh | sh
+
+      - name: Run tests
+        run: |
+          ./tests/test.ros
diff --git a/01-hello-sdl.lisp b/01-hello-sdl.lisp
new file mode 100644
index 0000000..2d1a366
--- /dev/null
+++ b/01-hello-sdl.lisp
@@ -0,0 +1,21 @@
+(defpackage #:sdl2-tutorial-01-hello-sdl
+  (:use :cl)
+  (:export :run))
+
+(in-package :sdl2-tutorial-01-hello-sdl)
+
+(defparameter *screen-width* 640)
+(defparameter *screen-height* 480)
+
+(defun run()
+  (sdl2:with-init (:video)
+    (sdl2:with-window (window :title "SDL2 Tutorial 01"
+                              :w *screen-width*
+                              :h *screen-height*
+                              :flags '(:shown))
+      (let ((screen-surface (sdl2:get-window-surface window)))
+        (sdl2:fill-rect screen-surface
+                        nil
+                        (sdl2:map-rgb (sdl2:surface-format screen-surface) 255 255 255))
+        (sdl2:update-window window)
+        (sdl2:delay 2000)))))
diff --git a/02-getting-an-image-on-the-screen.lisp b/02-getting-an-image-on-the-screen.lisp
new file mode 100644
index 0000000..bca48a0
--- /dev/null
+++ b/02-getting-an-image-on-the-screen.lisp
@@ -0,0 +1,34 @@
+(defpackage #:sdl2-tutorial-02-getting-an-image-on-the-screen
+  (:use :cl)
+  (:export :run)
+  (:import-from :sdl2-tutorial-utils :asset-pathname))
+
+(in-package :sdl2-tutorial-02-getting-an-image-on-the-screen)
+
+(defparameter *screen-width* 640)
+(defparameter *screen-height* 480)
+
+(defmacro with-window-surface ((window surface) &body body)
+  `(sdl2:with-init (:video)
+     (sdl2:with-window (,window
+                        :title "SDL2 Tutorial 02"
+                        :w *screen-width*
+                        :h *screen-height*
+                        :flags '(:shown))
+       (let ((,surface (sdl2:get-window-surface ,window)))
+         ,@body))))
+
+(defun load-image (filename)
+  (let ((image (sdl2:load-bmp filename)))
+    (if (autowrap:wrapper-null-p image)
+        (error "cannot load image ~a (check that file exists)" filename)
+        image)))
+
+(defun run()
+  (with-window-surface (window screen-surface)
+    (let ((image (load-image (asset-pathname #P"./assets/02/hello_world.bmp"))))
+      (sdl2:blit-surface image nil screen-surface nil)
+      (sdl2:update-window window)
+      (sdl2:delay 2000)
+      ;; clean up
+      (sdl2:free-surface image))))
diff --git a/03-event-driven-programming.lisp b/03-event-driven-programming.lisp
new file mode 100644
index 0000000..07565c9
--- /dev/null
+++ b/03-event-driven-programming.lisp
@@ -0,0 +1,38 @@
+(defpackage #:sdl2-tutorial-03-event-driven-programming
+  (:use :cl)
+  (:export :run)
+  (:import-from :sdl2-tutorial-utils :asset-pathname))
+
+(in-package :sdl2-tutorial-03-event-driven-programming)
+
+(defparameter *screen-width* 640)
+(defparameter *screen-height* 480)
+
+(defmacro with-window-surface ((window surface) &body body)
+  `(sdl2:with-init (:video)
+     (sdl2:with-window (,window
+                        :title "SDL2 Tutorial 03"
+                        :w *screen-width*
+                        :h *screen-height*
+                        :flags '(:shown))
+       (let ((,surface (sdl2:get-window-surface ,window)))
+         ,@body))))
+
+(defun load-image (pathname)
+  (let ((image (sdl2:load-bmp pathname)))
+    (if (autowrap:wrapper-null-p image)
+        (error "cannot load image ~a (check that file exists)" pathname)
+        image)))
+
+(defun run ()
+  (with-window-surface (window screen-surface)
+    (let ((image (load-image (asset-pathname #P"./assets/03/exit.bmp"))))
+      (sdl2:with-event-loop (:method :poll)
+        (:quit () t)
+        (:idle ()
+               (sdl2:blit-surface image nil screen-surface nil)
+               (sdl2:update-window window)
+               ;; reduce cpu usage
+               (sdl2:delay 100)))
+      ;; clean up
+      (sdl2:free-surface image))))
diff --git a/04-key-presses.lisp b/04-key-presses.lisp
new file mode 100644
index 0000000..ce8e38a
--- /dev/null
+++ b/04-key-presses.lisp
@@ -0,0 +1,53 @@
+(defpackage #:sdl2-tutorial-04-key-presses
+  (:use :cl)
+  (:export :run)
+  (:import-from :sdl2-tutorial-utils :asset-pathname))
+
+(in-package :sdl2-tutorial-04-key-presses)
+
+(defparameter *screen-width* 640)
+(defparameter *screen-height* 480)
+
+(defmacro with-window-surface ((window surface) &body body)
+  `(sdl2:with-init (:video)
+     (sdl2:with-window (,window
+                        :title "SDL2 Tutorial 04"
+                        :w *screen-width*
+                        :h *screen-height*
+                        :flags '(:shown))
+       (let ((,surface (sdl2:get-window-surface ,window)))
+         ,@body))))
+
+(defun load-image (pathname)
+  (let ((image (sdl2:load-bmp pathname)))
+    (if (autowrap:wrapper-null-p image)
+        (error "cannot load image ~a (check that file exists)" pathname)
+        image)))
+
+(defun load-media ()
+  (list :default (load-image (asset-Pathname #P"./assets/04/press.bmp"))
+        :up (load-image (asset-pathname #P"./assets/04/up.bmp"))
+        :down (load-image (asset-pathname #P"./assets/04/down.bmp"))
+        :left (load-image (asset-pathname #P"./assets/04/left.bmp"))
+        :right (load-image (asset-pathname #P"./assets/04/right.bmp"))))
+
+(defun run ()
+  (with-window-surface (window screen-surface)
+    (let* ((images (load-media))
+           (image (getf images :default)))
+      (sdl2:with-event-loop (:method :poll)
+        (:quit () t)
+        (:keydown (:keysym keysym)
+                  (setf image (getf images (case (sdl2:scancode keysym)
+                                             (:scancode-up :up)
+                                             (:scancode-down :down)
+                                             (:scancode-left :left)
+                                             (:scancode-right :right)
+                                             (t :default)))))
+        (:idle ()
+               (sdl2:blit-surface image nil screen-surface nil)
+               (sdl2:update-window window)
+               ;; reduce cpu usage
+               (sdl2:delay 100)))
+      ;; clean up
+      (mapc #'sdl2:free-surface (remove-if #'symbolp images)))))
diff --git a/05-optimized-surface-loading-and-soft-stretching.lisp b/05-optimized-surface-loading-and-soft-stretching.lisp
new file mode 100644
index 0000000..e285037
--- /dev/null
+++ b/05-optimized-surface-loading-and-soft-stretching.lisp
@@ -0,0 +1,41 @@
+(defpackage #:sdl2-tutorial-05-optimized-surface-loading-and-soft-stretching
+  (:use :cl)
+  (:export :run)
+  (:import-from :sdl2-tutorial-utils :asset-pathname))
+
+(in-package :sdl2-tutorial-05-optimized-surface-loading-and-soft-stretching)
+
+(defparameter *screen-width* 640)
+(defparameter *screen-height* 480)
+
+(defmacro with-window-surface ((window surface) &body body)
+  `(sdl2:with-init (:video)
+     (sdl2:with-window (,window
+                        :title "SDL2 Tutorial 05"
+                        :w *screen-width*
+                        :h *screen-height*
+                        :flags '(:shown))
+       (let ((,surface (sdl2:get-window-surface ,window)))
+         ,@body))))
+
+(defun load-surface (pathname pixel-format)
+  (let ((image (sdl2:load-bmp pathname)))
+    (if (autowrap:wrapper-null-p image)
+        (error "cannot load image ~a (check that file exists)" pathname)
+        (sdl2:convert-surface-format image pixel-format))))
+
+(defun run ()
+  (with-window-surface (window screen-surface)
+    (let ((image-surface (load-surface (asset-pathname #P"./assets/05/stretch.bmp")
+                                       (sdl2:surface-format-format screen-surface)))
+          (rect (sdl2:make-rect 0 0 *screen-width* *screen-height*)))
+      (sdl2:with-event-loop (:method :poll)
+        (:quit () t)
+        (:idle ()
+               (sdl2:blit-scaled image-surface
+                                 nil
+                                 screen-surface
+                                 rect)
+               (sdl2:update-window window)))
+      ;; clean up
+      (sdl2:free-surface image-surface))))
diff --git a/06-extension-libraries-and-loading-other-image-formats.lisp b/06-extension-libraries-and-loading-other-image-formats.lisp
new file mode 100644
index 0000000..ce40cc6
--- /dev/null
+++ b/06-extension-libraries-and-loading-other-image-formats.lisp
@@ -0,0 +1,40 @@
+(defpackage #:sdl2-tutorial-06-extension-libraries-and-loading-other-image-formats
+  (:use :cl)
+  (:export :run)
+  (:import-from :sdl2-tutorial-utils :asset-pathname))
+
+(in-package :sdl2-tutorial-06-extension-libraries-and-loading-other-image-formats)
+
+(defparameter *screen-width* 640)
+(defparameter *screen-height* 480)
+
+(defmacro with-window-surface ((window surface) &body body)
+  `(sdl2:with-init (:video)
+     (sdl2:with-window (,window
+                        :title "SDL2 Tutorial 06"
+                        :w *screen-width*
+                        :h *screen-height*
+                        :flags '(:shown))
+       (let ((,surface (sdl2:get-window-surface ,window)))
+         (sdl2-image:init '(:png))
+         ,@body
+         (sdl2-image:quit)))))
+
+(defun load-surface (pathname pixel-format)
+  (let ((surface (sdl2-image:load-image pathname)))
+    (prog1 (sdl2:convert-surface-format surface pixel-format)
+      (sdl2:free-surface surface))))
+
+(defun run ()
+  (with-window-surface (window screen-surface)
+    (let ((image-surface (load-surface (asset-pathname #P"assets/06/loaded.png")
+                                       (sdl2:surface-format-format screen-surface)))
+          (rect (sdl2:make-rect 0 0 *screen-width* *screen-height*)))
+      (sdl2:with-event-loop (:method :poll)
+        (:quit () t)
+        (:idle ()
+               (sdl2:blit-scaled image-surface nil screen-surface rect)
+               (sdl2:update-window window)))
+
+      ;; cleanup
+      (sdl2:free-surface image-surface))))
diff --git a/7/main.lisp b/07-texture-loading-and-rendering.lisp
similarity index 51%
rename from 7/main.lisp
rename to 07-texture-loading-and-rendering.lisp
index 833491c..eded968 100644
--- a/7/main.lisp
+++ b/07-texture-loading-and-rendering.lisp
@@ -1,8 +1,9 @@
-(defpackage #:sdl2-tutorial-7
-  (:use :common-lisp)
-  (:export :main))
+(defpackage #:sdl2-tutorial-07-texture-loading-and-rendering
+  (:use :cl)
+  (:export :run)
+  (:import-from :sdl2-tutorial-utils :asset-pathname))
 
-(in-package :sdl2-tutorial-7)
+(in-package :sdl2-tutorial-07-texture-loading-and-rendering)
 
 (defparameter *screen-width* 640)
 (defparameter *screen-height* 480)
@@ -10,24 +11,30 @@
 (defmacro with-window-renderer ((window renderer) &body body)
   `(sdl2:with-init (:video)
      (sdl2:with-window (,window
-                        :title "SDL2 Tutorial"
+                        :title "SDL2 Tutorial 07"
                         :w *screen-width*
                         :h *screen-height*
                         :flags '(:shown))
        (sdl2:with-renderer (,renderer ,window :index -1 :flags '(:accelerated))
-                           ,@body))))
+         ,@body))))
 
-(defun load-texture (renderer filename)
-  (sdl2:create-texture-from-surface renderer (sdl2-image:load-image filename)))
 
-(defun main()
+(defun load-texture (renderer pathname)
+  (let ((surface (sdl2-image:load-image pathname)))
+    (prog1 (sdl2:create-texture-from-surface renderer surface)
+      (sdl2:free-surface surface))))
+
+(defun run ()
   (with-window-renderer (window renderer)
     (sdl2-image:init '(:png))
     (sdl2:set-render-draw-color renderer #xFF #xFF #xFF #xFF)
-    (let ((texture (load-texture renderer "7/texture.png")))
+    (let ((texture (load-texture renderer (asset-pathname #P"./assets/07/texture.png"))))
       (sdl2:with-event-loop (:method :poll)
         (:quit () t)
         (:idle ()
                (sdl2:render-clear renderer)
                (sdl2:render-copy renderer texture)
-               (sdl2:render-present renderer))))))
+               (sdl2:render-present renderer)))
+
+      ;; clean up
+      (sdl2:destroy-texture texture))))
diff --git a/08-geometry-rendering.lisp b/08-geometry-rendering.lisp
new file mode 100644
index 0000000..976b6bc
--- /dev/null
+++ b/08-geometry-rendering.lisp
@@ -0,0 +1,60 @@
+(defpackage #:sdl2-tutorial-08-geometry-rendering
+  (:use :cl)
+  (:export :run))
+
+(in-package :sdl2-tutorial-08-geometry-rendering)
+
+(defparameter *screen-width* 640)
+(defparameter *screen-height* 480)
+
+(defmacro with-window-renderer ((window renderer) &body body)
+  `(sdl2:with-init (:video)
+     (sdl2:with-window (,window
+                        :title "SDL2 Tutorial 08"
+                        :w *screen-width*
+                        :h *screen-height*
+                        :flags '(:shown))
+       (sdl2:with-renderer (,renderer ,window :index -1 :flags '(:accelerated))
+         ,@body))))
+
+(defun run ()
+  (with-window-renderer (window renderer)
+    (sdl2-image:init '(:png))
+    (sdl2:with-event-loop (:method :poll)
+      (:quit () t)
+      (:idle ()
+             ;; Clear screen
+             (sdl2:set-render-draw-color renderer #xFF #xFF #xFF #xFF)
+             (sdl2:render-clear renderer)
+
+             ;; Render red filled quad
+             (sdl2:with-rects ((fill-rect (/ *screen-width* 4)
+                                          (/ *screen-height* 4)
+                                          (/ *screen-width* 2)
+                                          (/ *screen-height* 2)))
+               (sdl2:set-render-draw-color renderer #xFF #x00 #x00 #xFF)
+               (sdl2:render-fill-rect renderer fill-rect))
+
+             ;; Render green outlined quad
+             (sdl2:with-rects ((outline-rect (round (/ *screen-width* 6))
+                                             (round (/ *screen-height* 8))
+                                             (round (* 2/3 *screen-width*))
+                                             (round (* 2/3 *screen-height*))))
+               (sdl2:set-render-draw-color renderer #x00 #xFF #x00 #xFF)
+               (sdl2:render-draw-rect renderer outline-rect))
+
+             ;; Draw blue horizontal line
+             (sdl2:set-render-draw-color renderer #x00 #x00 #xFF #xFF)
+             (sdl2:render-draw-line renderer
+                                    0
+                                    (/ *screen-height* 2)
+                                    *screen-width*
+                                    (/ *screen-height* 2))
+
+             ;; Draw vertical line of yellow dots
+             (sdl2:set-render-draw-color renderer #xFF #xFF #x00 #xFF)
+             (loop for i from 0 below *screen-height* by 4
+                   do (sdl2::render-draw-point renderer (/ *screen-width* 2) i))
+
+             ;; Update screen
+             (sdl2:render-present renderer)))))
diff --git a/09-the-viewport.lisp b/09-the-viewport.lisp
new file mode 100644
index 0000000..e05484e
--- /dev/null
+++ b/09-the-viewport.lisp
@@ -0,0 +1,62 @@
+(defpackage #:sdl2-tutorial-09-the-viewport
+  (:use :cl)
+  (:export :run)
+  (:import-from :sdl2-tutorial-utils :asset-pathname))
+
+(in-package :sdl2-tutorial-09-the-viewport)
+
+(defparameter *screen-width* 640)
+(defparameter *screen-height* 480)
+
+(defmacro with-window-renderer ((window renderer) &body body)
+  `(sdl2:with-init (:video)
+     (sdl2:with-window (,window
+                        :title "SDL2 Tutorial 09"
+                        :w *screen-width*
+                        :h *screen-height*
+                        :flags '(:shown))
+       (sdl2:with-renderer (,renderer ,window :index -1 :flags '(:accelerated))
+         ,@body))))
+
+(defun load-texture (renderer pathname)
+  (let ((surface (sdl2-image:load-image pathname)))
+    (prog1 (sdl2:create-texture-from-surface renderer surface)
+      (sdl2:free-surface surface))))
+
+(defun run ()
+  (with-window-renderer (window renderer)
+    (sdl2-image:init '(:png))
+
+    (let ((texture (load-texture renderer (asset-pathname #P"assets/09/texture.png"))))
+      (sdl2:with-event-loop (:method :poll)
+        (:quit () t)
+        (:idle ()
+               ;; Clear screen
+               (sdl2:set-render-draw-color renderer #xFF #xFF #xFF #xFF)
+               (sdl2:render-clear renderer)
+
+               ;; Top left corner viewport
+               (sdl2:with-rects ((top-left-viewport 0
+                                                    0
+                                                    (/ *screen-width* 2)
+                                                    (/ *screen-height* 2))
+                                 (top-right-viewport (/ *screen-width* 2)
+                                                     0
+                                                     (/ *screen-width* 2)
+                                                     (/ *screen-height* 2))
+                                 (bottom-viewport 0
+                                                  (/ *screen-height* 2)
+                                                  *screen-width*
+                                                  (/ *screen-height* 2)))
+                 (sdl2:render-set-viewport renderer top-left-viewport)
+                 (sdl2:render-copy renderer texture) ; Render texture to screen
+
+                 (sdl2:render-set-viewport renderer top-right-viewport)
+                 (sdl2:render-copy renderer texture)
+
+                 (sdl2:render-set-viewport renderer bottom-viewport)
+                 (sdl2:render-copy renderer texture))
+
+               (sdl2:render-present renderer)))
+      ;; cleanup
+      (sdl2:destroy-texture texture))))
diff --git a/1/main.lisp b/1/main.lisp
deleted file mode 100644
index 7be644b..0000000
--- a/1/main.lisp
+++ /dev/null
@@ -1,21 +0,0 @@
-(defpackage #:sdl2-tutorial-1
-  (:use :common-lisp)
-  (:export :main))
-
-(in-package :sdl2-tutorial-1)
-
-(defparameter *screen-width* 640)
-(defparameter *screen-height* 480)
-
-(defun main(&key (delay 2000))
-  (sdl2:with-init (:video)
-    (sdl2:with-window (window :title "SDL2 Window" :w *screen-width* :h *screen-height*)
-      (let ((screen-surface (sdl2:get-window-surface window)))
-        (sdl2:fill-rect screen-surface
-                        nil
-                        (sdl2:map-rgb (sdl2:surface-format screen-surface) 255 255 255))
-        (sdl2:update-window window)
-	(sdl2:with-event-loop (:method :poll)
-	  (:quit () t)
-	  (:idle ()
-		 (sdl2:delay delay)))))))
diff --git a/10/main.lisp b/10-color-keying.lisp
similarity index 54%
rename from 10/main.lisp
rename to 10-color-keying.lisp
index 4c9d341..dac4510 100644
--- a/10/main.lisp
+++ b/10-color-keying.lisp
@@ -1,8 +1,9 @@
-(defpackage #:sdl2-tutorial-10
-  (:use :common-lisp)
-  (:export :main))
+(defpackage #:sdl2-tutorial-10-color-keying
+  (:use :cl)
+  (:export :run)
+  (:import-from :sdl2-tutorial-utils :asset-pathname))
 
-(in-package :sdl2-tutorial-10)
+(in-package :sdl2-tutorial-10-color-keying)
 
 (defparameter *screen-width* 640)
 (defparameter *screen-height* 480)
@@ -18,18 +19,22 @@
     :accessor tex-height
     :initform 0)
    (texture
-    :accessor tex-texture
     :initform nil)))
 
-(defun load-texture-from-file (renderer filename)
+(defun free-tex (tex)
+  (with-slots (texture) tex
+    (sdl2:destroy-texture texture)))
+
+(defun load-texture-from-file (renderer pathname)
   (let ((tex (make-instance 'tex :renderer renderer)))
     (with-slots (renderer texture  width height) tex
-      (let ((surface (sdl2-image:load-image filename)))
+      (let ((surface (sdl2-image:load-image pathname)))
         (setf width (sdl2:surface-width surface))
         (setf height (sdl2:surface-height surface))
         (sdl2:set-color-key surface :true (sdl2:map-rgb (sdl2:surface-format surface)
                                                         0 #xFF #xFF))
-        (setf texture (sdl2:create-texture-from-surface renderer surface))))
+        (setf texture (sdl2:create-texture-from-surface renderer surface))
+        (sdl2:free-surface surface)))
     tex))
 
 (defun render (tex x y)
@@ -39,28 +44,28 @@
 (defmacro with-window-renderer ((window renderer) &body body)
   `(sdl2:with-init (:video)
      (sdl2:with-window (,window
-                        :title "SDL2 Tutorial"
+                        :title "SDL2 Tutorial 10"
                         :w *screen-width*
                         :h *screen-height*
                         :flags '(:shown))
        (sdl2:with-renderer (,renderer ,window :index -1 :flags '(:accelerated))
-                           ,@body))))
-
-(defun load-texture (renderer filename)
-  (sdl2:create-texture-from-surface renderer (sdl2-image:load-image filename)))
+         ,@body))))
 
-(defun main()
+(defun run()
   (with-window-renderer (window renderer)
     (sdl2-image:init '(:png))
-    (let ((background-tex (load-texture-from-file renderer "10/background.png"))
-          (player-tex (load-texture-from-file renderer "10/player.png")))
-          (sdl2:with-event-loop (:method :poll)
-            (:quit () t)
-            (:idle ()
-                   (sdl2:set-render-draw-color renderer #xFF #xFF #xFF #xFF)
-                   (sdl2:render-clear renderer)
+    (let ((background-tex (load-texture-from-file renderer (asset-pathname #P"assets/10/background.png")))
+          (player-tex (load-texture-from-file renderer (asset-pathname #P"assets/10/player.png"))))
+      (sdl2:with-event-loop ()
+        (:quit () t)
+        (:idle ()
+               (sdl2:set-render-draw-color renderer #xFF #xFF #xFF #xFF)
+               (sdl2:render-clear renderer)
 
-                   (render background-tex 0 0)
-                   (render player-tex 240 190)
+               (render background-tex 0 0)
+               (render player-tex 240 190)
 
-                   (sdl2:render-present renderer))))))
+               (sdl2:render-present renderer)))
+      ;; clean up
+      (free-tex background-tex)
+      (free-tex player-tex))))
diff --git a/11/main.lisp b/11-clip-rendering-and-sprite-sheets.lisp
similarity index 55%
rename from 11/main.lisp
rename to 11-clip-rendering-and-sprite-sheets.lisp
index d4ff3f8..79e4d43 100644
--- a/11/main.lisp
+++ b/11-clip-rendering-and-sprite-sheets.lisp
@@ -1,8 +1,9 @@
-(defpackage #:sdl2-tutorial-11
-  (:use :common-lisp)
-  (:export :main))
+(defpackage #:sdl2-tutorial-11-clip-rendering-and-sprite-sheets
+  (:use :cl)
+  (:export :run)
+  (:import-from :sdl2-tutorial-utils :asset-pathname))
 
-(in-package :sdl2-tutorial-11)
+(in-package :sdl2-tutorial-11-clip-rendering-and-sprite-sheets)
 
 (defparameter *screen-width* 640)
 (defparameter *screen-height* 480)
@@ -21,15 +22,16 @@
     :accessor tex-texture
     :initform nil)))
 
-(defun load-texture-from-file (renderer filename)
+(defun load-texture-from-file (renderer pathname)
   (let ((tex (make-instance 'tex :renderer renderer)))
     (with-slots (renderer texture  width height) tex
-      (let ((surface (sdl2-image:load-image filename)))
+      (let ((surface (sdl2-image:load-image pathname)))
         (setf width (sdl2:surface-width surface))
         (setf height (sdl2:surface-height surface))
         (sdl2:set-color-key surface :true (sdl2:map-rgb (sdl2:surface-format surface)
                                                         0 #xFF #xFF))
-        (setf texture (sdl2:create-texture-from-surface renderer surface))))
+        (setf texture (sdl2:create-texture-from-surface renderer surface))
+        (sdl2:free-surface surface)))
     tex))
 
 (defun render (tex x y &key clip)
@@ -45,46 +47,45 @@
 (defmacro with-window-renderer ((window renderer) &body body)
   `(sdl2:with-init (:video)
      (sdl2:with-window (,window
-                        :title "SDL2 Tutorial"
+                        :title "SDL2 Tutorial 11"
                         :w *screen-width*
                         :h *screen-height*
                         :flags '(:shown))
        (sdl2:with-renderer (,renderer ,window :index -1 :flags '(:accelerated))
          ,@body))))
 
-(defun main()
+(defun run ()
   (with-window-renderer (window renderer)
     (sdl2-image:init '(:png))
-    (let ((spritesheet-tex (load-texture-from-file renderer "11/spritesheet.png"))
-          (sprite-clips '(:top-left (0 0 100 100)
-                          :top-right (100 0 100 100)
-                          :bottom-left (0 100 100 100)
-                          :bottom-right (100 100 100 100))))
+    (let ((spritesheet-tex (load-texture-from-file renderer (asset-pathname #P"assets/11/spritesheet.png")))
+          (top-left (sdl2:make-rect 0 0 100 100))
+          (top-right (sdl2:make-rect 100 0 100 100))
+          (bottom-left (sdl2:make-rect 0 100 100 100))
+          (bottom-right (sdl2:make-rect 100 100 100 100)))
       (sdl2:with-event-loop (:method :poll)
         (:quit () t)
         (:idle ()
                (sdl2:set-render-draw-color renderer #xFF #xFF #xFF #xFF)
                (sdl2:render-clear renderer)
 
-               (let ((rect (apply #'sdl2::make-rect (getf sprite-clips :top-left))))
-                 (render spritesheet-tex 0 0 :clip rect))
+               (render spritesheet-tex
+                       0
+                       0
+                       :clip top-left)
 
-               (let ((rect (apply #'sdl2::make-rect (getf sprite-clips :top-right))))
-                 (render spritesheet-tex
-                         (- *screen-width* (sdl2:rect-width rect))
-                         0
-                         :clip rect))
+               (render spritesheet-tex
+                       (- *screen-width* (sdl2:rect-width top-right))
+                       0
+                       :clip top-right)
 
-               (let ((rect (apply #'sdl2::make-rect (getf sprite-clips :bottom-left))))
-                 (render spritesheet-tex
-                         0
-                         (- *screen-height* (sdl2:rect-height rect))
-                         :clip rect))
+               (render spritesheet-tex
+                       0
+                       (- *screen-height* (sdl2:rect-height bottom-left))
+                       :clip bottom-left)
 
-               (let ((rect (apply #'sdl2::make-rect (getf sprite-clips :bottom-right))))
-                 (render spritesheet-tex
-                         (- *screen-width* (sdl2:rect-width rect))
-                         (- *screen-height* (sdl2:rect-height rect))
-                         :clip rect))
+               (render spritesheet-tex
+                       (- *screen-width* (sdl2:rect-width bottom-right))
+                       (- *screen-height* (sdl2:rect-height bottom-right))
+                       :clip bottom-right)
 
                (sdl2:render-present renderer))))))
diff --git a/12/main.lisp b/12-color-modulation.lisp
similarity index 89%
rename from 12/main.lisp
rename to 12-color-modulation.lisp
index d6c803f..bcfa908 100644
--- a/12/main.lisp
+++ b/12-color-modulation.lisp
@@ -1,8 +1,9 @@
-(defpackage #:sdl2-tutorial-12
-  (:use :common-lisp)
-  (:export :main))
+(defpackage #:sdl2-tutorial-12-color-modulation
+  (:use :cl)
+  (:export :run)
+  (:import-from :sdl2-tutorial-utils :asset-pathname))
 
-(in-package :sdl2-tutorial-12)
+(in-package #:sdl2-tutorial-12-color-modulation)
 
 (defparameter *screen-width* 640)
 (defparameter *screen-height* 480)
@@ -48,7 +49,7 @@
 (defmacro with-window-renderer ((window renderer) &body body)
   `(sdl2:with-init (:video)
      (sdl2:with-window (,window
-                        :title "SDL2 Tutorial"
+                        :title "SDL2 Tutorial 12"
                         :w *screen-width*
                         :h *screen-height*
                         :flags '(:shown))
@@ -64,10 +65,10 @@
 (defmacro clamp-decf (x delta)
   `(setf ,x (clamp (- ,x ,delta))))
 
-(defun main()
+(defun run ()
   (with-window-renderer (window renderer)
     (sdl2-image:init '(:png))
-    (let ((texture (load-texture-from-file renderer "12/texture.png"))
+    (let ((texture (load-texture-from-file renderer (asset-pathname #P"assets/12/texture.png")))
           (r 255)
           (g 255)
           (b 255)
diff --git a/13/main.lisp b/13-alpha-blending.lisp
similarity index 86%
rename from 13/main.lisp
rename to 13-alpha-blending.lisp
index 0f62a18..2b74747 100644
--- a/13/main.lisp
+++ b/13-alpha-blending.lisp
@@ -1,8 +1,9 @@
-(defpackage #:sdl2-tutorial-13
-  (:use :common-lisp)
-  (:export :main))
+(defpackage #:sdl2-tutorial-13-alpha-blending
+  (:use :cl)
+  (:export :run)
+  (:import-from :sdl2-tutorial-utils :asset-pathname))
 
-(in-package :sdl2-tutorial-13)
+(in-package #:sdl2-tutorial-13-alpha-blending)
 
 (defparameter *screen-width* 640)
 (defparameter *screen-height* 480)
@@ -54,7 +55,7 @@
 (defmacro with-window-renderer ((window renderer) &body body)
   `(sdl2:with-init (:video)
      (sdl2:with-window (,window
-                        :title "SDL2 Tutorial"
+                        :title "SDL2 Tutorial 13"
                         :w *screen-width*
                         :h *screen-height*
                         :flags '(:shown))
@@ -70,11 +71,11 @@
 (defmacro clamp-decf (x delta)
   `(setf ,x (clamp (- ,x ,delta))))
 
-(defun main()
+(defun run ()
   (with-window-renderer (window renderer)
     (sdl2-image:init '(:png))
-    (let ((bg-texture (load-texture-from-file renderer "13/fadein.png"))
-          (modulated-texture (load-texture-from-file renderer "13/fadeout.png"))
+    (let ((bg-texture (load-texture-from-file renderer (asset-pathname "assets/13/fadein.png")))
+          (modulated-texture (load-texture-from-file renderer (asset-pathname "assets/13/fadeout.png")))
           (alpha 255)
           (delta 32))
       (set-blend-mode modulated-texture :blend)
diff --git a/14/main.lisp b/14-animated-sprites-and-vsync.lisp
similarity index 89%
rename from 14/main.lisp
rename to 14-animated-sprites-and-vsync.lisp
index 05def6b..428617a 100644
--- a/14/main.lisp
+++ b/14-animated-sprites-and-vsync.lisp
@@ -1,8 +1,9 @@
-(defpackage #:sdl2-tutorial-14
-  (:use :common-lisp)
-  (:export :main))
+(defpackage #:sdl2-tutorial-14-animated-sprites-and-vsync
+  (:use :cl)
+  (:export :run)
+  (:import-from :sdl2-tutorial-utils :asset-pathname))
 
-(in-package :sdl2-tutorial-14)
+(in-package #:sdl2-tutorial-14-animated-sprites-and-vsync)
 
 (defparameter *screen-width* 640)
 (defparameter *screen-height* 480)
@@ -54,7 +55,7 @@
 (defmacro with-window-renderer ((window renderer) &body body)
   `(sdl2:with-init (:video)
      (sdl2:with-window (,window
-                        :title "SDL2 Tutorial"
+                        :title "SDL2 Tutorial 14"
                         :w *screen-width*
                         :h *screen-height*
                         :flags '(:shown))
@@ -70,10 +71,10 @@
 (defmacro clamp-decf (x delta)
   `(setf ,x (clamp (- ,x ,delta))))
 
-(defun main()
+(defun run ()
   (with-window-renderer (window renderer)
     (sdl2-image:init '(:png))
-    (let ((spritesheet-tex (load-texture-from-file renderer "14/character.png"))
+    (let ((spritesheet-tex (load-texture-from-file renderer (asset-pathname "assets/14/character.png")))
           (clip (sdl2:make-rect 0 0 64 96))
           (sprite-frames 4)
           (current-sprite-frame 0)
diff --git a/15/main.lisp b/15-rotation-and-flipping.lisp
similarity index 89%
rename from 15/main.lisp
rename to 15-rotation-and-flipping.lisp
index 99699a0..9d980e8 100644
--- a/15/main.lisp
+++ b/15-rotation-and-flipping.lisp
@@ -1,8 +1,9 @@
-(defpackage #:sdl2-tutorial-15
-  (:use :common-lisp)
-  (:export :main))
+(defpackage #:sdl2-tutorial-15-rotation-and-flipping
+  (:use :cl)
+  (:export :run)
+  (:import-from :sdl2-tutorial-utils :asset-pathname))
 
-(in-package :sdl2-tutorial-15)
+(in-package #:sdl2-tutorial-15-rotation-and-flipping)
 
 (defparameter *screen-width* 640)
 (defparameter *screen-height* 480)
@@ -51,17 +52,17 @@
 (defmacro with-window-renderer ((window renderer) &body body)
   `(sdl2:with-init (:video)
      (sdl2:with-window (,window
-                        :title "SDL2 Tutorial"
+                        :title "SDL2 Tutorial 15"
                         :w *screen-width*
                         :h *screen-height*
                         :flags '(:shown))
        (sdl2:with-renderer (,renderer ,window :index -1 :flags '(:accelerated))
          ,@body))))
 
-(defun main()
+(defun run ()
   (with-window-renderer (window renderer)
     (sdl2-image:init '(:png))
-    (let ((texture (load-texture-from-file renderer "15/arrow.png"))
+    (let ((texture (load-texture-from-file renderer (asset-pathname "assets/15/arrow.png")))
           (flip :none)
           (degrees 0)
           (delta 60))
diff --git a/16/main.lisp b/16-true-type-fonts.lisp
similarity index 83%
rename from 16/main.lisp
rename to 16-true-type-fonts.lisp
index 367933f..82d328d 100644
--- a/16/main.lisp
+++ b/16-true-type-fonts.lisp
@@ -1,8 +1,9 @@
-(defpackage #:sdl2-tutorial-16
-  (:use :common-lisp)
-  (:export :main))
+(defpackage #:sdl2-tutorial-16-true-type-fonts
+  (:use :cl)
+  (:export :run)
+  (:import-from :sdl2-tutorial-utils :asset-pathname))
 
-(in-package :sdl2-tutorial-16)
+(in-package #:sdl2-tutorial-16-true-type-fonts)
 
 (defparameter *screen-width* 640)
 (defparameter *screen-height* 480)
@@ -23,6 +24,10 @@
     :accessor tex-texture
     :initform nil)))
 
+(defun free-tex (tex)
+  (with-slots (texture) tex
+    (sdl2:destroy-texture texture)))
+
 (defun load-texture-from-file (renderer filename)
   (let ((tex (make-instance 'tex :renderer renderer)))
     (with-slots (renderer texture  width height) tex
@@ -46,7 +51,7 @@
 (defun set-color (tex r g b)
   (sdl2:set-texture-color-mod (tex-texture tex) r g b))
 
-(defun render (tex x y &key clip angle center flip)
+(defun render (tex x y &key clip angle center (flip :none))
   (with-slots (renderer texture width height) tex
     (sdl2:render-copy-ex renderer
                          texture
@@ -62,18 +67,18 @@
 (defmacro with-window-renderer ((window renderer) &body body)
   `(sdl2:with-init (:video)
      (sdl2:with-window (,window
-                        :title "SDL2 Tutorial"
+                        :title "SDL2 Tutorial 16"
                         :w *screen-width*
                         :h *screen-height*
                         :flags '(:shown))
        (sdl2:with-renderer (,renderer ,window :index -1 :flags '(:accelerated))
          ,@body))))
 
-(defun main()
+(defun run ()
   (with-window-renderer (window renderer)
     (sdl2-image:init '(:png))
     (sdl2-ttf:init)
-    (setf *font* (sdl2-ttf:open-font "16/Pacifico.ttf" 28))
+    (setf *font* (sdl2-ttf:open-font (asset-pathname "assets/16/Pacifico.ttf") 28))
     (let ((texture (load-texture-from-text renderer "The quick brown fox jumps over the lazy dog")))
       (sdl2:with-event-loop (:method :poll)
         (:quit () t)
@@ -83,6 +88,8 @@
                (render texture
                        (round (/ (- *screen-width* (tex-width texture)) 2))
                        (round (/ (- *screen-height* (tex-height texture)) 2)))
-               (sdl2:render-present renderer))))
+               (sdl2:render-present renderer)))
+      ;; clean up
+      (free-tex texture))
     (sdl2-ttf:quit)
     (sdl2-image:quit)))
diff --git a/2/main.lisp b/2/main.lisp
deleted file mode 100644
index 411891f..0000000
--- a/2/main.lisp
+++ /dev/null
@@ -1,30 +0,0 @@
-(defpackage #:sdl2-tutorial-2
-  (:use :common-lisp)
-  (:export :main))
-
-(in-package :sdl2-tutorial-2)
-
-(defparameter *screen-width* 640)
-(defparameter *screen-height* 480)
-
-(defmacro with-window-surface ((window surface) &body body)
-  `(sdl2:with-init (:video)
-     (sdl2:with-window (,window
-                        :title "SDL2 Tutorial"
-                        :w *screen-width*
-                        :h *screen-height*
-                        :flags '(:shown))
-       (let ((,surface (sdl2:get-window-surface ,window)))
-         ,@body))))
-
-(defun main(&key (delay 2000))
-  (with-window-surface (window screen-surface)
-    (sdl2:blit-surface (sdl2:load-bmp "2/hello_world.bmp")
-                       nil
-                       screen-surface
-                       nil)
-    (sdl2:update-window window)
-    (sdl2:with-event-loop (:method :poll)
-      (:quit () t)
-      (:idle ()
-	     (sdl2:delay delay)))))
diff --git a/3/main.lisp b/3/main.lisp
deleted file mode 100644
index 17d6354..0000000
--- a/3/main.lisp
+++ /dev/null
@@ -1,28 +0,0 @@
-(defpackage #:sdl2-tutorial-3
-  (:use :common-lisp)
-  (:export :main))
-
-(in-package :sdl2-tutorial-3)
-
-(defparameter *screen-width* 640)
-(defparameter *screen-height* 480)
-
-(defmacro with-window-surface ((window surface) &body body)
-  `(sdl2:with-init (:video)
-     (sdl2:with-window (,window
-                        :title "SDL2 Tutorial"
-                        :w *screen-width*
-                        :h *screen-height*
-                        :flags '(:shown))
-       (let ((,surface (sdl2:get-window-surface ,window)))
-         ,@body))))
-
-(defun main()
-  (with-window-surface (window screen-surface)
-    (let ((image (sdl2:load-bmp "3/exit.bmp")))
-      (sdl2:with-event-loop (:method :poll)
-        (:quit () t)
-        (:idle ()
-               (sdl2:blit-surface image nil screen-surface nil)
-               (sdl2:update-window window)
-               (sdl2:delay 100))))))    ;reduce cpu usage
diff --git a/4/main.lisp b/4/main.lisp
deleted file mode 100644
index 8ca43c2..0000000
--- a/4/main.lisp
+++ /dev/null
@@ -1,43 +0,0 @@
-(defpackage #:sdl2-tutorial-4
-  (:use :common-lisp)
-  (:export :main))
-
-(in-package :sdl2-tutorial-4)
-
-(defparameter *screen-width* 640)
-(defparameter *screen-height* 480)
-
-(defmacro with-window-surface ((window surface) &body body)
-  `(sdl2:with-init (:video)
-     (sdl2:with-window (,window
-                        :title "SDL2 Tutorial"
-                        :w *screen-width*
-                        :h *screen-height*
-                        :flags '(:shown))
-       (let ((,surface (sdl2:get-window-surface ,window)))
-         ,@body))))
-
-(defun load-media ()
-  (list :default (sdl2:load-bmp "4/press.bmp")
-        :up (sdl2:load-bmp "4/up.bmp")
-        :down (sdl2:load-bmp "4/down.bmp")
-        :left (sdl2:load-bmp "4/left.bmp")
-        :right (sdl2:load-bmp "4/right.bmp")))
-
-(defun main()
-  (with-window-surface (window screen-surface)
-    (let* ((images (load-media))
-           (image (getf images :default)))
-      (sdl2:with-event-loop (:method :poll)
-        (:quit () t)
-        (:keydown (:keysym keysym)
-                  (case (sdl2:scancode keysym)
-                    (:scancode-up (setf image (getf images :up)))
-                    (:scancode-down (setf image (getf images :down)))
-                    (:scancode-left (setf image (getf images :left)))
-                    (:scancode-right (setf image (getf images :right)))
-                    (t (setf image (getf images :default)))))
-        (:idle ()
-               (sdl2:blit-surface image nil screen-surface nil)
-               (sdl2:update-window window)
-               (sdl2:delay 100))))))    ;reduce cpu usage
diff --git a/5/main.lisp b/5/main.lisp
deleted file mode 100644
index 34fd608..0000000
--- a/5/main.lisp
+++ /dev/null
@@ -1,34 +0,0 @@
-(defpackage #:sdl2-tutorial-5
-  (:use :common-lisp)
-  (:export :main))
-
-(in-package :sdl2-tutorial-5)
-
-(defparameter *screen-width* 640)
-(defparameter *screen-height* 480)
-
-(defmacro with-window-surface ((window surface) &body body)
-  `(sdl2:with-init (:video)
-     (sdl2:with-window (,window
-                        :title "SDL2 Tutorial"
-                        :w *screen-width*
-                        :h *screen-height*
-                        :flags '(:shown))
-       (let ((,surface (sdl2:get-window-surface ,window)))
-         ,@body))))
-
-(defun load-surface (filename &optional pixel-format)
-  (sdl2:convert-surface-format (sdl2:load-bmp filename) pixel-format))
-
-(defun main()
-  (with-window-surface (window screen-surface)
-    (let ((image-surface (load-surface "5/stretch.bmp" (sdl2:surface-format-format screen-surface)))
-          (rect (sdl2:make-rect 0 0 *screen-width* *screen-height*)))
-      (sdl2:with-event-loop (:method :poll)
-        (:quit () t)
-        (:idle ()
-               (sdl2:blit-scaled image-surface
-                                 nil
-                                 screen-surface
-                                 rect)
-               (sdl2:update-window window))))))
diff --git a/6/loaded.png b/6/loaded.png
deleted file mode 100644
index 66ee6c6..0000000
Binary files a/6/loaded.png and /dev/null differ
diff --git a/6/main.lisp b/6/main.lisp
deleted file mode 100644
index d19a729..0000000
--- a/6/main.lisp
+++ /dev/null
@@ -1,35 +0,0 @@
-(defpackage #:sdl2-tutorial-6
-  (:use :common-lisp)
-  (:export :main))
-
-(in-package :sdl2-tutorial-6)
-
-(defparameter *screen-width* 640)
-(defparameter *screen-height* 480)
-
-(defmacro with-window-surface ((window surface) &body body)
-  `(sdl2:with-init (:video)
-     (sdl2:with-window (,window
-                        :title "SDL2 Tutorial"
-                        :w *screen-width*
-                        :h *screen-height*
-                        :flags '(:shown))
-       (let ((,surface (sdl2:get-window-surface ,window)))
-         ,@body))))
-
-(defun load-surface (filename &optional pixel-format)
-  (sdl2:convert-surface-format (sdl2-image:load-image filename) pixel-format))
-
-(defun main()
-  (with-window-surface (window screen-surface)
-    (sdl2-image:init '(:png))
-    (let ((image-surface (load-surface "6/loaded.png" (sdl2:surface-format-format screen-surface)))
-          (rect (sdl2:make-rect 0 0 *screen-width* *screen-height*)))
-      (sdl2:with-event-loop (:method :poll)
-        (:quit () t)
-        (:idle ()
-               (sdl2:blit-scaled image-surface
-                                 nil
-                                 screen-surface
-                                 rect)
-               (sdl2:update-window window))))))
diff --git a/8/main.lisp b/8/main.lisp
deleted file mode 100644
index 47e4596..0000000
--- a/8/main.lisp
+++ /dev/null
@@ -1,52 +0,0 @@
-(defpackage #:sdl2-tutorial-8
-  (:use :common-lisp)
-  (:export :main))
-
-(in-package :sdl2-tutorial-8)
-
-(defparameter *screen-width* 640)
-(defparameter *screen-height* 480)
-
-(defmacro with-window-renderer ((window renderer) &body body)
-  `(sdl2:with-init (:video)
-     (sdl2:with-window (,window
-                        :title "SDL2 Tutorial"
-                        :w *screen-width*
-                        :h *screen-height*
-                        :flags '(:shown))
-       (sdl2:with-renderer (,renderer ,window :index -1 :flags '(:accelerated))
-                           ,@body))))
-
-(defun load-texture (renderer filename)
-  (sdl2:create-texture-from-surface renderer (sdl2-image:load-image filename)))
-
-(defun main()
-  (with-window-renderer (window renderer)
-    (sdl2-image:init '(:png))
-    (sdl2:with-event-loop (:method :poll)
-      (:quit () t)
-      (:idle ()
-             (sdl2:set-render-draw-color renderer #xFF #xFF #xFF #xFF)
-             (sdl2:render-clear renderer)
-             (sdl2:set-render-draw-color renderer #xFF #x00 #x00 #xFF)
-             (sdl2:render-fill-rect renderer
-                                    (sdl2:make-rect (/ *screen-width* 4)
-                                                    (/ *screen-height* 4)
-                                                    (/ *screen-width* 2)
-                                                    (/ *screen-height* 2)))
-             (sdl2:set-render-draw-color renderer #x00 #xFF #x00 #xFF)
-             (sdl2:render-draw-rect renderer
-                                    (sdl2:make-rect (round (/ *screen-width* 6))
-                                                    (round (/ *screen-height* 8))
-                                                    (round (* 2/3 *screen-width*))
-                                                    (round (* 2/3 *screen-height*))))
-             (sdl2:set-render-draw-color renderer #x00 #x00 #xFF #xFF)
-             (sdl2:render-draw-line renderer
-                                    0
-                                    (/ *screen-height* 2)
-                                    *screen-width*
-                                    (/ *screen-height* 2))
-             (sdl2:set-render-draw-color renderer #xFF #xFF #x00 #xFF)
-             (loop for i from 0 below *screen-height* by 4
-                  do (sdl2::render-draw-point renderer (/ *screen-width* 2) i))
-             (sdl2:render-present renderer)))))
diff --git a/9/main.lisp b/9/main.lisp
deleted file mode 100644
index c640ac7..0000000
--- a/9/main.lisp
+++ /dev/null
@@ -1,55 +0,0 @@
-(defpackage #:sdl2-tutorial-9
-  (:use :common-lisp)
-  (:export :main))
-
-(in-package :sdl2-tutorial-9)
-
-(defparameter *screen-width* 640)
-(defparameter *screen-height* 480)
-
-(defmacro with-window-renderer ((window renderer) &body body)
-  `(sdl2:with-init (:video)
-     (sdl2:with-window (,window
-                        :title "SDL2 Tutorial"
-                        :w *screen-width*
-                        :h *screen-height*
-                        :flags '(:shown))
-       (sdl2:with-renderer (,renderer ,window :index -1 :flags '(:accelerated))
-                           ,@body))))
-
-(defun load-texture (renderer filename)
-  (sdl2:create-texture-from-surface renderer (sdl2-image:load-image filename)))
-
-(defun main()
-  (with-window-renderer (window renderer)
-    (sdl2-image:init '(:png))
-
-    (let ((texture (load-texture renderer "9/texture.png")))
-          (sdl2:with-event-loop (:method :poll)
-            (:quit () t)
-            (:idle ()
-                   (sdl2:set-render-draw-color renderer #xFF #xFF #xFF #xFF)
-                   (sdl2:render-clear renderer)
-
-                   (sdl2:render-set-viewport renderer
-                                             (sdl2:make-rect 0
-                                                             0
-                                                             (/ *screen-width* 2)
-                                                             (/ *screen-height* 2)))
-                   (sdl2:render-copy renderer texture)
-
-                   (sdl2:render-set-viewport renderer
-                                             (sdl2:make-rect (/ *screen-width* 2)
-                                                             0
-                                                             (/ *screen-width* 2)
-                                                             (/ *screen-height* 2)))
-                   (sdl2:render-copy renderer texture)
-
-                   (sdl2:render-set-viewport renderer
-                                             (sdl2:make-rect 0
-                                                             (/ *screen-height* 2)
-                                                             *screen-width*
-                                                             (/ *screen-height* 2)))
-                   (sdl2:render-copy renderer texture)
-
-                   (sdl2:render-present renderer))))))
diff --git a/README.md b/README.md
index 62a10c1..ea28450 100644
--- a/README.md
+++ b/README.md
@@ -1,54 +1,50 @@
+![ci](https://github.com/TatriX/cl-sdl2-tutorial/actions/workflows/ci.yml/badge.svg)
+
 # Common Lisp SDL2 tutorials
 Adapted from http://lazyfoo.net/tutorials/SDL/
 
-
 ## Installing the SDL2 Libraries
 
   The tutorial requires that SDL2, SDL2 Image, and SDL2 TTF are installed before
   running the examples.
 
-### Mac OS X
-
-Mac OS X requires each library to be downloaded and copied to
-$HOME/Library/Frameworks or /Library/Frameworks.
-
- Library Name | Download Link
- ------------ | -------------
- SDL2         | https://www.libsdl.org/download-2.0.php
- SDL2 Image   | https://www.libsdl.org/projects/SDL_image
- SDL2 TTF     | https://www.libsdl.org/projects/SDL_ttf
-
-Running the tutorials will cause Catalina to report that the framework cannot be
-opened because the developer cannot be verified. The workaround for this problem
-is the following:
+  See instructions for [Linux](README_LINUX.md) and [macOS](README_MACOS.md) respectively.
 
-1. Navigate to System Preferences -> Security & Privacy -> General on the Mac
 
-2. Run repl.sh
+## Installation
 
-3. When the dialog appears about the developer not being verified, click the
-"Cancel" button.
+Using [quicklisp](https://www.quicklisp.org/beta/):
+```
+git clone https://github.com/TatriX/cl-sdl2-tutorial/ ~/quicklisp/local-projects
+```
 
-4. Examine the Security & Privacy screen for a button called "Allow Anyway" for
-the framework. Click the "Allow Anyway" button with the identified framework.
+```lisp
+(ql:quickload :sdl2-tutorial)
+```
 
-5. The verification dialog will now appear a second time, but there will be an
-option to "Open" the framework. Click "Open".
-
-6. Repeat steps 3 through 5 for the different frameworks.
-
-### Linux
-
-The SDL2 libraries can be installed on a Debian based system with the command
-below.
-
-	apt install libsdl2-2.0 libsdl2-image-2.0 libsdl2-ttf-2.0
+or [asdf](https://common-lisp.net/project/asdf/)
+```
+git clone https://github.com/TatriX/cl-sdl2-tutorial/ ~/common-lisp
+```
 
+```lisp
+(asdf:load-system "sdl2-tutorial")
+```
 
 ## Running the Examples
 
-A repl.sh script is provided that loads SDL2-TUTORIAL with quicklisp and then
-starts up a swank thread on port 4005 for repl connections.
-
-	1. ./repl.sh
-	2. (sdl2-tutorial:main #'sdl2-tutorial-1:main)
+Tutorial packages are named as `sdl2-tutorial-XX-DESC`
+where `XX` is a number starting from `01`.
+
+```lisp
+(sdl2-tutorial-01-hello-sdl:run)
+;;
+(sdl2-tutorial-04-key-presses:run)
+```
+
+## Notes
+As far as I can tell `cl-sdl2` in most cases doesn't free created
+objects. This means it's up to a user to do so. I've tried to free
+allocated resources, but as with any manual memory management I could
+miss something. If you notice anything, please create an issue or even
+send a PR!
diff --git a/README_LINUX.md b/README_LINUX.md
new file mode 100644
index 0000000..704be81
--- /dev/null
+++ b/README_LINUX.md
@@ -0,0 +1,12 @@
+## Installing the SDL2 Libraries Linux
+
+## Debian
+
+The SDL2 libraries can be installed on a Debian based system with the command
+below.
+
+	apt install libsdl2-dev libsdl2-image-dev libsdl2-ttf-dev
+
+## Arch
+
+    sudo pacman -S sdl2 sdl2_image sdl2_ttf
diff --git a/README_MACOS.md b/README_MACOS.md
new file mode 100644
index 0000000..a7a6dd1
--- /dev/null
+++ b/README_MACOS.md
@@ -0,0 +1,29 @@
+### Mac OS X
+
+Mac OS X requires each library to be downloaded and copied to
+$HOME/Library/Frameworks or /Library/Frameworks.
+
+ Library Name | Download Link
+ ------------ | -------------
+ SDL2         | https://www.libsdl.org/download-2.0.php
+ SDL2 Image   | https://www.libsdl.org/projects/SDL_image
+ SDL2 TTF     | https://www.libsdl.org/projects/SDL_ttf
+
+Running the tutorials will cause Catalina to report that the framework cannot be
+opened because the developer cannot be verified. The workaround for this problem
+is the following:
+
+1. Navigate to System Preferences -> Security & Privacy -> General on the Mac
+
+2. Run repl.sh
+
+3. When the dialog appears about the developer not being verified, click the
+"Cancel" button.
+
+4. Examine the Security & Privacy screen for a button called "Allow Anyway" for
+the framework. Click the "Allow Anyway" button with the identified framework.
+
+5. The verification dialog will now appear a second time, but there will be an
+option to "Open" the framework. Click "Open".
+
+6. Repeat steps 3 through 5 for the different frameworks.
diff --git a/2/hello_world.bmp b/assets/02/hello_world.bmp
similarity index 100%
rename from 2/hello_world.bmp
rename to assets/02/hello_world.bmp
diff --git a/3/exit.bmp b/assets/03/exit.bmp
similarity index 100%
rename from 3/exit.bmp
rename to assets/03/exit.bmp
diff --git a/4/down.bmp b/assets/04/down.bmp
similarity index 100%
rename from 4/down.bmp
rename to assets/04/down.bmp
diff --git a/4/left.bmp b/assets/04/left.bmp
similarity index 100%
rename from 4/left.bmp
rename to assets/04/left.bmp
diff --git a/4/press.bmp b/assets/04/press.bmp
similarity index 100%
rename from 4/press.bmp
rename to assets/04/press.bmp
diff --git a/4/right.bmp b/assets/04/right.bmp
similarity index 100%
rename from 4/right.bmp
rename to assets/04/right.bmp
diff --git a/4/up.bmp b/assets/04/up.bmp
similarity index 100%
rename from 4/up.bmp
rename to assets/04/up.bmp
diff --git a/5/stretch.bmp b/assets/05/stretch.bmp
similarity index 50%
rename from 5/stretch.bmp
rename to assets/05/stretch.bmp
index 3d3b153..8457f19 100644
Binary files a/5/stretch.bmp and b/assets/05/stretch.bmp differ
diff --git a/assets/06/loaded.png b/assets/06/loaded.png
new file mode 100644
index 0000000..0618717
Binary files /dev/null and b/assets/06/loaded.png differ
diff --git a/7/texture.png b/assets/07/texture.png
similarity index 100%
rename from 7/texture.png
rename to assets/07/texture.png
diff --git a/9/texture.png b/assets/09/texture.png
similarity index 100%
rename from 9/texture.png
rename to assets/09/texture.png
diff --git a/10/background.png b/assets/10/background.png
similarity index 100%
rename from 10/background.png
rename to assets/10/background.png
diff --git a/10/player.png b/assets/10/player.png
similarity index 100%
rename from 10/player.png
rename to assets/10/player.png
diff --git a/11/spritesheet.png b/assets/11/spritesheet.png
similarity index 100%
rename from 11/spritesheet.png
rename to assets/11/spritesheet.png
diff --git a/12/texture.png b/assets/12/texture.png
similarity index 100%
rename from 12/texture.png
rename to assets/12/texture.png
diff --git a/13/fadein.png b/assets/13/fadein.png
similarity index 100%
rename from 13/fadein.png
rename to assets/13/fadein.png
diff --git a/13/fadeout.png b/assets/13/fadeout.png
similarity index 100%
rename from 13/fadeout.png
rename to assets/13/fadeout.png
diff --git a/14/character.png b/assets/14/character.png
similarity index 100%
rename from 14/character.png
rename to assets/14/character.png
diff --git a/15/arrow.png b/assets/15/arrow.png
similarity index 100%
rename from 15/arrow.png
rename to assets/15/arrow.png
diff --git a/16/Pacifico.ttf b/assets/16/Pacifico.ttf
similarity index 100%
rename from 16/Pacifico.ttf
rename to assets/16/Pacifico.ttf
diff --git a/repl.sh b/repl.sh
deleted file mode 100755
index 1293363..0000000
--- a/repl.sh
+++ /dev/null
@@ -1,4 +0,0 @@
-#!/bin/sh
-
-sbcl --eval "(ql:quickload \"sdl2-tutorial\")" \
-     --eval "(sdl2-tutorial:create-swank-server)"
diff --git a/sdl2-tutorial.asd b/sdl2-tutorial.asd
index f72be9c..7350e3a 100644
--- a/sdl2-tutorial.asd
+++ b/sdl2-tutorial.asd
@@ -1,22 +1,30 @@
 (defsystem "sdl2-tutorial"
   :description "SDL2 Tutorial based upon http://lazyfoo.net/tutorials/SDL"
-  :version "0.0.1"
+  :version "0.2.0"
+  :author "TatriX <tatrics@gmail.com>"
   :licence "Public Domain"
-  :depends-on ("bordeaux-threads" "sdl2" "sdl2-image" "sdl2-ttf" "swank")
-  :components ((:file "1/main")
-	       (:file "2/main")
-	       (:file "3/main")
-	       (:file "4/main")
-	       (:file "5/main")
-	       (:file "6/main")
-	       (:file "7/main")
-	       (:file "8/main")
-	       (:file "9/main")
-	       (:file "10/main")
-	       (:file "11/main")
-	       (:file "12/main")
-	       (:file "13/main")
-	       (:file "14/main")
-	       (:file "15/main")
-	       (:file "16/main")
-	       (:file "sdl2-tutorial")))
+  :depends-on ("bordeaux-threads" "sdl2" "sdl2-image" "sdl2-ttf")
+  :components ((:file "utils")
+               (:file "01-hello-sdl")
+               (:file "02-getting-an-image-on-the-screen")
+               (:file "03-event-driven-programming")
+               (:file "04-key-presses")
+               (:file "05-optimized-surface-loading-and-soft-stretching")
+               (:file "06-extension-libraries-and-loading-other-image-formats")
+               (:file "07-texture-loading-and-rendering")
+               (:file "08-geometry-rendering")
+               (:file "09-the-viewport")
+               (:file "10-color-keying")
+               (:file "11-clip-rendering-and-sprite-sheets")
+               (:file "12-color-modulation")
+               (:file "13-alpha-blending")
+               (:file "14-animated-sprites-and-vsync")
+               (:file "15-rotation-and-flipping")
+               (:file "16-true-type-fonts"))
+  :in-order-to ((test-op (test-op "sdl2-tutorial/tests"))))
+
+
+(defsystem "sdl2-tutorial/tests"
+  :depends-on ("parachute")
+  :components ((:file "tests/tests"))
+  :perform (test-op (op c) (symbol-call :parachute :test :sdl2-tutorial-tests)))
diff --git a/sdl2-tutorial.lisp b/sdl2-tutorial.lisp
deleted file mode 100644
index 7346b9c..0000000
--- a/sdl2-tutorial.lisp
+++ /dev/null
@@ -1,11 +0,0 @@
-(defpackage :sdl2-tutorial
-  (:use cl bt)
-  (:export :main :create-swank-server))
-
-(in-package :sdl2-tutorial)
-
-(defun create-swank-server()
-  (bt:make-thread (lambda () (swank:create-server :port 4005 :dont-close t))))
-
-(defun main(fn)
-  (sdl2:make-this-thread-main fn))
diff --git a/tests/test.ros b/tests/test.ros
new file mode 100755
index 0000000..9410a3e
--- /dev/null
+++ b/tests/test.ros
@@ -0,0 +1,17 @@
+#!/bin/sh
+#|-*- mode:lisp -*-|#
+#|
+exec ros -Q -- $0 "$@"
+|#
+(progn ;;init forms
+  (ros:ensure-asdf)
+  #+quicklisp(ql:quickload '(sdl2-tutorial sdl2-tutorial/tests) :silent t))
+
+(defpackage :ros.script.test
+  (:use :cl))
+(in-package :ros.script.test)
+
+(defun main (&rest argv)
+  (declare (ignorable argv))
+  (parachute:test-toplevel :sdl2-tutorial-tests))
+;;; vim: set ft=lisp lisp:
diff --git a/tests/tests.lisp b/tests/tests.lisp
new file mode 100644
index 0000000..f735303
--- /dev/null
+++ b/tests/tests.lisp
@@ -0,0 +1,7 @@
+(defpackage #:sdl2-tutorial-tests
+  (:use :cl :parachute))
+
+(in-package #:sdl2-tutorial-tests)
+
+(define-test hello
+  (true t))
diff --git a/utils.lisp b/utils.lisp
new file mode 100644
index 0000000..a1a74c4
--- /dev/null
+++ b/utils.lisp
@@ -0,0 +1,13 @@
+(defpackage #:sdl2-tutorial-utils
+  (:use :cl)
+  (:export :asset-path))
+
+(in-package #:sdl2-tutorial-utils)
+
+(defun asset-pathname (pathname)
+  "Return an absolute filename for a given PATHNAME relative to
+`:sdl2-tutorial' asdf system directory.
+
+This function doesn't prepend 'assets/' to the PATHNAME to not
+interfere with your editor filename completion."
+  (merge-pathnames pathname (asdf:system-source-directory :sdl2-tutorial)))