title: Adding same sprite many times in SpriteKit
body: <p>I am building simple game with Sprite Kit in which level is built from identical rectangular blocks. But when I add to many block (i.e. 1000), game becomes very slow (FPS drops to 20). Here's how I add blocks to scene:</p>
  
  <pre><code>-(void)drawLevel
  {
      SKSpriteNode *shelf = [SKSpriteNode spriteNodeWithTexture:_initialLevel.earthBoxTexture];
      shelf.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:shelf.size];
      shelf.physicsBody.dynamic=NO;
      shelf.physicsBody.categoryBitMask = platformCategory;
  
      for (NSValue *positionValue in _initialLevel.boxPositions)
      {
          shelf.position = positionValue.CGPointValue;
          [_platformsNode addChild:[shelf copy]];
      }
  
      [_world addChild:_platformsNode];
  }
  </code></pre>
  
  <p>_world is a child of main scene. I create "shelf" once and than copy it. How should I do that to obtain good FPS?</p>
  
  <p>App was tested on the iPhone 5.</p>