code: function( x, y, r, styles ){
  
              var graphics = new PIXI.Graphics();
              this.setStyles( graphics, styles );
              graphics.drawCircle( x, y, r );
              graphics.endFill();
              return graphics;
          }
docs: PixiRenderer#createCircle( x, y, r, styles ) -> PIXI.Graphics
  - x (Number): The x coord
  - y (Number): The y coord
  - r (Number): The circle radius
  - styles (Object): The styles configuration
  + (PIXI.Graphics): A graphic object representing a circle.
  
  Create a circle for use in PIXI stage