Update bouncing ball

Chapter 13/bouncing ball

@@ -18,8 +18,8 @@ const ctx = canvas.getContext("2d");
 const ballSize = 10;
 let x = canvas.width/2;
 let y = canvas.height/2;
-let dx = 1;
-let dy = 1;
+let dirX = 1;
+let dirY = 1;
 function drawBall() {
     ctx.beginPath();
     ctx.arc(x, y, ballSize, 0, Math.PI*2);
@@ -27,19 +27,19 @@ function drawBall() {
     ctx.fill();
     ctx.closePath();
 }
-function draw() {
+function move() {
     ctx.clearRect(0, 0, canvas.width, canvas.height);
     drawBall();
-    if(x + dx > canvas.width-ballSize || x + dx < ballSize) {
-        dx *= -1;
+    if(x  > canvas.width-ballSize || x  < ballSize) {
+        dirX *= -1;
     }
-    if(y + dy > canvas.height-ballSize || y + dy < ballSize) {
-        dy *= -1;
+    if(y > canvas.height-ballSize || y < ballSize) {
+        dirY *= -1;
     }
-    x += dx;
-    y += dy;
+    x += dirX;
+    y += dirY;
 }
-setInterval(draw, 10);
+setInterval(move, 10);
     </script>
 </body>