title: What is wrong with the coordinate system in this SpriteKit setup?
body: <p>I created a SKView which presents an SKScene subclass like this:</p>
  
  <pre><code>SKView *skv = [[SKView alloc] initWithFrame:self.view.bounds];
  [self.view addSubview:skv];
  
  self.skScene = [[TestScene alloc] initWithSize:v.bounds.size];
  [skv presentScene:_skScene];
  </code></pre>
  
  <p>Then to see coordinate system origin, I add a small 10x10 colored square to the scene.</p>
  
  <pre><code>SKSpriteNode *ori = [SKSpriteNode spriteNodeWithColor:[UIColor greenColor] size:CGSizeMake(10,10)];
  [self addChild:ori];
  </code></pre>
  
  <p>You can see green square in lower left corner:</p>
  
  <p><img src="https://i.stack.imgur.com/fizzf.png" alt="green dot in lower left corner"></p>
  
  <p>From what I thought, SpriteKit coordinate system is such that origin is always in center. But in the scene the origin is in lower left corner. When I add a child node to {0,0} it appears in lower left corner as well.</p>
  
  <p>When I add a SKSpriteNode and position it {0,0} in the scene, it appears in lower left corner. But it is centered around scene origin in lower left corner (clipped off half to left, and half to bottom).</p>
  
  <p>But now it gets more confusing. When I add a SKSpriteNode to another SKSpriteNode, the sub-sprite is CENTERED in the parent.</p>
  
  <p>So does it mean the Scene coordinate system works different than the sprite coordinate system?</p>
  
  <p>Recap:</p>
  
  <ul>
  <li>When I position a sprite in scene at {0,0}, it appears in bottom
  left, clipped off 50% (centered around origin). </li>
  <li>When I position a sprite in a sprite at {0,0}, it appears centered in the sprite.</li>
  </ul>
  
  <p>Is my Scene configured wrong or is this the way it works?</p>