title: Make SKSprites register collision but not affect each other
body: <p>Im wanting to add powerups to my game but when my sprite hits the powerup sprite it throws him off course because the game has registered a collision and i guess physics come into play, when i tap the screen my sprite jumps in the air, hits the powerup and stops moving up and falls down again.</p>
  
  <p>I need the sprite to jump up, collect the powerup sprite and the score go up (score going up code is done) but i cannot figure out how to make the 2 sprites no register the collision.</p>
  
  <pre><code>    //Create the PowerUp Coin to add score
  func createCoin() {
  
      coinPlus5 = SKSpriteNode(imageNamed: "coin1")
      coinPlus5.name = "coinPlus5"
      coinPlus5.position.x = self.frame.size.width*2.6
      coinPlus5.position.y = CGFloat.randomBetweenNumbers(firstNum: -(self.frame.size.height / 2.8), secondNum: (self.frame.size.height / 2.4))
      coinPlus5.zPosition = 11
      coinPlus5.size = CGSize(width: 50, height: 50)
      hitPowerup = false
  
      // Add Physics Bodys
      coinPlus5.physicsBody = SKPhysicsBody(texture: coinPlus5.texture!, size: CGSize(width: coinPlus5.size.width, height: coinPlus5.size.height))
  
  
      //enemyBird1.physicsBody = SKPhysicsBody(circleOfRadius: self.size.height/13)
      coinPlus5.physicsBody?.allowsRotation = false
      coinPlus5.physicsBody?.affectedByGravity = false
      coinPlus5.physicsBody?.isDynamic = false
      // Add Collision Bitmasks
      coinPlus5.physicsBody?.categoryBitMask = ColliderType.Pipes
  </code></pre>
  
  <p>And the character sprite code is:</p>
  
  <pre><code> func initialise() {
  
      self.name = "Bird"
      self.zPosition = 3
      self.size = CGSize(width: 130, height: 110)
      self.anchorPoint = CGPoint(x: 0.5, y: 0.5)
  
  
  
  
  
  
      self.physicsBody = SKPhysicsBody(texture: self.texture!,
                                       size: CGSize(width: self.size.width,
                                                    height: self.size.height))
  
      // Add Physics Bodys
      self.physicsBody?.allowsRotation = false
      self.physicsBody?.affectedByGravity = false
      self.physicsBody?.mass = CGFloat(-100)
      // Add Collision Bitmasks
      self.physicsBody?.categoryBitMask = ColliderType.Bird
      self.physicsBody?.collisionBitMask = ColliderType.Ground | ColliderType.Pipes
      self.physicsBody?.contactTestBitMask = ColliderType.Ground | ColliderType.Pipes | ColliderType.Score
  
  
  }
  </code></pre>