code: function(x, y, r, styles, ctx){
  
              ctx = ctx || this.ctx;
  
              ctx.beginPath();
              this.setStyle( styles, ctx );
              ctx.arc(x, y, r, 0, Pi2, false);
              ctx.closePath();
              ctx.stroke();
              ctx.fill();
          }
docs: CanvasRenderer#drawCircle( x, y, r, styles[, ctx] )
  - x (Number): The x coord
  - y (Number): The y coord
  - r (Number): The circle radius
  - styles (Object): The styles configuration
  - ctx (Canvas2DContext): The canvas context
  
  Draw a circle to specified canvas context.