   gl = utils.getGLContext(canvas);
      gl.clearColor(...clearColor, 1);
      gl.clearDepth(1);
      gl.enable(gl.DEPTH_TEST);
      gl.depthFunc(gl.LESS);
      gl.blendFunc(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA);

      // Configure `program`
      program = new Program(gl, 'vertex-shader', 'fragment-shader');

      const attributes = [
        'aVertexPosition',
        'aVertexNormal',
        'aVertexColor'
      ];

      const uniforms = [
        'uProjectionMatrix',
        'uModelViewMatrix',
