title: Sprites are removed by themselfs as soon as they pass the screen height
body: <p>I'm currently trying SpriteKit for first time and using some actions. I was under the impression that every node/sprite you create you would need to remove it but for some reason they are removed by themselfs as soon as they pass the screen height. Is this a normal behavior in SpriteKit?</p>
  
  <p>Here is the code.
  I'm basically using an action to animate a sprite across the screen (from bottom to top in protrait-mode), the funny thing is that the node count stays at 0 no matter how many sprites I create, it actually counts them but it subtracts them as soon as they pass the screen height.  </p>
  
  <pre><code>-(void) shoot
  {
      bullet = [SKSpriteNode spriteNodeWithImageNamed:@"bullet"];
      bullet.position =  CGPointMake(airPlane.position.x, airPlane.position.y + 50);
      [self addChild:bullet];
  
      SKAction *moveBullet = [SKAction moveTo:CGPointMake(airPlane.position.x, self.size.height + 20) duration:0.5];
  
      [bullet runAction:moveBullet];
  }
  </code></pre>
  
  <p>If I change my action to where the sprite doesn't cross the screen height then the node count keeps the count.</p>
  
  <p>Change this line...</p>
  
  <pre><code>SKAction *moveBullet = [SKAction moveTo:CGPointMake(airPlane.position.x, self.size.height + 20) duration:0.5];
  </code></pre>
  
  <p>... to this </p>
  
  <pre><code>SKAction *moveBullet = [SKAction moveTo:CGPointMake(airPlane.position.x, self.size.height) duration:0.5];
  </code></pre>
  
  <p>Again Is this a normal behavior in SpriteKit?</p>
  
  <p>Thanks a lot</p>