ion: projectionMatrix,
      u_world: mat,
    });

    // calls gl.drawArrays or gl.drawElements
    twgl.drawBufferInfo(gl, cubeLinesBufferInfo, gl.LINES);
  }

  // Draw the scene.
  function render() {
    twgl.resizeCanvasToDisplaySize(gl.canvas);

    // Tell WebGL how to convert from clip space to pixels
    gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);

    gl.enable(gl.CULL_FACE);
    gl.enable(gl.DEPTH_TEST);

    // Clear the canvas AND the depth buffer.
    gl.clear(gl.COLOR_BUFFER_BIT |