docs: function (x, y, r) {
      return new BVG('polygon', x.constructor.name === 'Object' ? x : {
        x: x,
        y: y,
        r: r
      }, function (tag, data) {
        var points = [
          [data.x, data.y-data.r],
          [data.x-data.r/2*Math.sqrt(3), data.y+data.r/2],
          [data.x+data.r/2*Math.sqrt(3), data.y+data.r/2]
        ];
        tag.setAttribute('points', points.join(' '));
      });
    }