title: CGContextAddArc: how to create circle?
body: <p>I started working on my Tower defense project in Xcode with the new Spritekit framework and I wanted to add a visible radius (circle) around ANY tower that the player would create.</p>
  
  <p>So I created the following code:</p>
  
  <pre><code>// Place Towers
  -(void)mouseUp:(NSEvent *)theEvent {
      /* Called when a mouse click occurs */
  
      CGPoint location = [theEvent locationInNode:self];
  
      SKSpriteNode *sprite = [SKSpriteNode spriteNodeWithImageNamed:@"tower"];
  
      sprite.position = location;
      sprite.scale = 1.5;
  
      CGContextRef myContext = [[NSGraphicsContext currentContext] graphicsPort];
      CGContextAddArc(myContext, location.x, location.y, 10, 0, M_PI*2, YES);
      CGContextSetRGBStrokeColor(myContext, 0, 0, 225, 0);
  
      [self addChild:sprite];
  
  }
  </code></pre>
  
  <p>I'm not familiar with the angles and other things because I am doing this for the first time, so I'm just guessing that it should be like that.  I'm pretty sure that I missed something.</p>
  
  <p>Thanks for any advice (I await some great criticism).</p>