Time for action – updating the ball

The ball needs to move in a continuous motion without gravity affecting it. We'll have to take into account the side walls and the top and bottom walls. The velocity in the x and y direction have to reflect the other way when a collision happens on any of the boundaries. We need to set coordinates so that the ball is only allowed to move through and alert when it passes through the area below the paddle region. Let's perform the following steps:

Create a new function called function updateBall() below the removeBrick(event) function:
```
function updateBall()
```

Add in the ball movement:

  ball.x = ball.x + vx
  ball.y = ball.y + vy

Add in the ball movement for the x direction:
```
  if ball.x < 0 or ball.x + ball.width > display.contentWidth then
    vx = -vx
  end
```
The following screenshot shows the movement of ball in the x direction:
Add in
the ball movement for the y direction:
```
  if ball.y < 0 then 
    vy = -vy 
  end
```
The following screenshot shows the movement of the ball in the y direction:
Add in the ball movement when it collides with the bottom of the game play screen. Create the lost alert screen and a game event for "lose". Close the function with end:
```
  if ball.y + ball.height > paddle.y + paddle.height then 
    alertScreen("YOU LOSE!", "Play Again") gameEvent = "lose" 
  end
end
```
The following screenshot shows the lost alert screen when the ball collides with the bottom of the game play screen:

What just happened?

Everywhere the ball travels, proper direction change is needed when it hits the wall. Any time the ball hits the side walls, we used vx = -vx. When the ball hits the top boundary, vy = -vy is used. The only time the ball doesn't reflect the opposite direction is when it hits the bottom of the screen.

The alert screen displays the lose condition, which emphasizes to the player to play again. The gameEvent = "lose" statement will be used in another if statement to reset the current level.