Bouncing Ball program Would like ball to reappear at top and come down again <p>Right now in my program the ball bounces up and down on the Y axis. What i want is for the ball to only move in the downward direction. when it gets to the bottom of the screen I want it to reappears at the top and starts down again. Continually moving from top to bottom.</p> <pre><code>@implementation BounceViewController @synthesize ball; -(void) bounce{ ball.center = CGPointMake(ball.center.x+position.x, ball.center.y+position.y); { if(ball.center.y&gt;450 ||ball.center.y &lt;0) position.y = -position.y; } } - (void)viewDidLoad { position = CGPointMake(0, 10); [NSTimer scheduledTimerWithTimeInterval:.05 target:self selector:@selector(bounce) userInfo:nil repeats:YES]; [super viewDidLoad]; } - (void)viewDidUnload { [self setBall:nil]; [super viewDidUnload]; } @end </code></pre>