1, 5,

    7, 3, 0,
    7, 0, 4,
  ];

  var lineIndices = [
    0, 1,
    1, 2,
    2, 3,
    3, 0,
    4, 5,
    5, 6,
    6, 7,
    7, 4,
    0, 4,
    1, 5,
    2, 6,
    3, 7,
  ];

  var canvas = document.querySelector("#c");
  var gl = canvas.getContext("webgl", {preserveDrawingBuffer: true});
  var clock = 0;

  var program = webglUtils.createProgramFromScripts(
      gl, ["vertex-shader-2d", "fragment-shader-2d"]);
  gl.useProgram(program);

  var positionLoc = gl.getAttribLocation(program, "a_posi