Start working on pong example.

Doesn't work yet. Just committing what I have so far.

3 files changed, 82 insertions, 0 deletions

diff --git a/examples/images/ballBlue.png b/examples/images/ballBlue.png
new file mode 100644
index 0000000..b241812
--- /dev/null
+++ b/examples/images/ballBlue.png
diff --git a/examples/images/paddleBlue.png b/examples/images/paddleBlue.png
new file mode 100644
index 0000000..398be9d
--- /dev/null
+++ b/examples/images/paddleBlue.png
diff --git a/examples/pong.scm b/examples/pong.scm
new file mode 100644
index 0000000..5ff1979
--- /dev/null
+++ b/examples/pong.scm
@@ -0,0 +1,82 @@
+(use-modules (srfi srfi-1)
+             (srfi srfi-9)
+             (2d color)
+             (2d game)
+             (2d keyboard)
+             (2d math)
+             (2d rect)
+             (2d signals)
+             (2d sprite)
+             (2d texture)
+             (2d time)
+             (2d vector2)
+             (2d window))
+
+(define-record-type <paddle>
+  (%make-paddle y)
+  paddle?
+  (y paddle-y)
+  (speed paddle-speed))
+
+(define-record-type <ball>
+  (make-ball position velocity)
+  ball?
+  (position ball-position)
+  (velocity ball-velocity))
+
+(define window-width 640)
+(define window-height 480)
+(define half-width (/ window-width 2))
+(define half-height (/ window-height 2))
+
+(with-window (make-window #:title "FRP is cool"
+                          #:resolution (vector2 window-width
+                                                window-height)
+                          #:fullscreen? #f)
+  (define paddle-texture (load-texture "images/paddleBlue.png"))
+  (define ball-texture (load-texture "images/ballBlue.png"))
+
+  (define paddle-speed 5)
+  (define ball-speed 4)
+  (define ball-hitbox (make-rect -8 -8 16 16))
+
+  (define (move-paddle directions)
+    (signal-fold (lambda (new old)
+                   (clamp 0 window-height (+ (* new paddle-speed) old)))
+                 half-height
+                 (signal-lift vy (time-every directions))))
+
+  (define player1-paddle (move-paddle key-wasd))
+  (define player2-paddle (move-paddle key-arrows))
+
+  (define (wall-bounce position)
+    (let ((rect (rect-move ball-hitbox position)))
+      (cond ((> (rect-bottom rect) window-height)
+             (vector2 (vx position)
+                      (- (vy position))))
+            (else
+             position))))
+
+  (define ball (signal-fold (lambda (direction position)
+                              (wall-bounce (v+ (vscale direction ball-speed) position)))
+                            (vector2 half-width half-height)
+                            (time-every (make-signal #:init (vector2 1 1)))))
+
+  (define quit-on-esc
+    (signal-lift (lambda (down?)
+                   (when down?
+                     (quit-game)))
+                 (key-down? 'escape)))
+
+  (define draw
+    (let ((paddle-sprite (make-sprite paddle-texture))
+          (ball-sprite (make-sprite ball-texture)))
+      (lambda ()
+        (set-sprite-position! paddle-sprite (vector2 0 (signal-ref player1-paddle)))
+        (draw-sprite paddle-sprite)
+        (set-sprite-position! paddle-sprite (vector2 window-width (signal-ref player2-paddle)))
+        (draw-sprite paddle-sprite)
+        (set-sprite-position! ball-sprite ball)
+        (draw-sprite ball-sprite))))
+
+  (run-game #:draw draw))