[feat] moving sprite

game.scm

@@ -18,12 +18,15 @@
 (define canvas (get-element-by-id "canvas"))
 (define context (get-context canvas "2d"))
 
+(define *element-x* (/ game-width 2.0))
+
 ;; Draw
 (define (draw prev-time)
+  (clear-rect context 0.0 0.0 game-width game-height)
   (set-fill-color! context "#140c1c")
   (set-text-align! context "center")
   (set-font! context "bold 24px monospace")
-  (fill-text context "Hello, World! :)" (/ game-width 2.0) (/ game-height 2.0))
+  (fill-text context "Hello, World! :)" *element-x* (/ game-height 2.0))
   (request-animation-frame draw-callback))
 (define draw-callback (procedure->external draw))
 
@@ -34,3 +37,20 @@
 
 (dprint "game-height" game-height)
 (console-log canvas)
+
+;; Input
+(define key:left "ArrowLeft")
+(define key:right "ArrowRight")
+
+(define (on-key-down event)
+  (let ((key (keyboard-event-code event)))
+    (cond
+     ((string=? key key:left)
+      (dprint "key:" key)
+      (set! *element-x* (- *element-x* 10)))
+     ((string=? key key:right)
+      (dprint "key:" key)
+      (set! *element-x* (+ *element-x* 10))))))
+
+(add-event-listener! (current-document) "keydown"
+                     (procedure->external on-key-down))