Now we have our basic game world, we have walls, and a ball that will drop off of the bottom of the screen. We need to turn our attention to the only piece of the game the user directly controls: the paddle. Let's look at how we build it:
-(void) buildPaddleAtStartingPosition:(CGPoint)startPos {
// Create the paddle
paddle = [PhysicsSprite spriteWithSpriteFrameName:
@"paddle.png"];
paddle.position = startPos;
paddle.tag = kPaddle;
[bricksheet addChild: paddle];
// Create paddle body
b2BodyDef paddleBodyDef;
paddleBodyDef.type = b2_dynamicBody;
paddleBodyDef.position.Set(startPos.x/PTM_RATIO,
startPos.y/PTM_RATIO);
paddleBodyDef.userData = paddle;
paddleBody = world->CreateBody(&paddleBodyDef);
// Connect the body to the sprite
[paddle setPhysicsBody:paddleBody];
// Build normal size fixure
...