         for touch: AnyObject in touches {
             let location = touch.locationInNode(self)
             
-            var isRacket = false
             for r in self.children {
                 if r.name == "racket" {
                     if location.y < ((self.size.height * 2) / 3) {
                         let seq = SKAction.sequence([SKAction.moveTo(location, duration: 0.25),
                             SKAction.moveTo(initPostision!, duration: 0.5)])
                         r.runAction(seq)
-                        isRacket = true
                     }
                 }
-            }
-            if !isRacket {
-                addBall(location)
             }
         }
     }

    
    let CATEGORY_RACKET: UInt32 = 0x00000001
    let CATEGORY_BALL: UInt32 = 0x00000010
    
    // not supported construct.
    required init(coder aDecoder: NSCoder) {

        self.physicsWorld.contactDelegate = self
        self.physicsBody = SKPhysicsBody(edgeLoopFromRect: self.frame)
        self.physicsWorld.gravity = CGVectorMake(0.0, -5.0)
        self.physicsBody?.categoryBitMask = CATEGORY_ROUND
        self.physicsBody?.contactTestBitMask = CATEGORY_BALL
        
        drawBackground()
    }
