text: let GeometryFactory = gr.lib.fundamental.Geometry.GeometryFactory;
  let Geometry = gr.lib.fundamental.Geometry.Geometry;
  GeometryFactory.addType('custom', {}, function(gl,attrs){
    let geometry = new Geometry(gl);
    let position = [
       0.0,  0.5,  0.0,
      -0.5, -0.5,  0.0,
       0.5, -0.5,  0.0
    ];
    let indices = [0, 1, 2];
    geometry.addAttributes(position, {
      POSITION:{size: 3}
    });
    geometry.addIndex('default', indices, WebGLRenderingContext.TRIANGLES);
    return geometry;
  });
  
  gr(function() {
    let $$ = gr('#canvas');
  });
  