Workshop › Breakout › Step 10 of 39

Bounce off the ceiling

What we are doing

The top wall works the same way, with one safer trick: instead of flipping vy, we force it to point down with Math.abs.

```js
if (ball.y - BALL_R < 0) {
  ball.vy = Math.abs(ball.vy)
  ball.y = BALL_R
}
```

ball.y - BALL_R < 0 is true when the top edge is above the canvas.
Math.abs drops the minus sign: Math.abs(-4) is 4, which always means "down".
ball.y = BALL_R puts the ball just below the ceiling.

Write the new if right under the closing } of the side-wall if.

Skills: Collision detection, Velocity and gravity