e = "#version 100\nattribute vec2 aVertexPosition; void main(void) { gl_Position = vec4(aVertexPosition, 1.0, 1.0); }";
  var fragmentShaderSource = document.getElementById("shader_source").value;;

  var vertices = [
    -1.0,  1.0,
    -1.0, -1.0,
     1.0, -1.0,
     1.0,  1.0
  ];

  var indicies = [
    0, 1, 2,   2, 3, 0
  ];
  
  stop();
  console.log("Start");
  
  // WebGL
  var canvas = document.getElementById("opengl-canvas");
  var gl = null;
  try {
    gl = canvas.getContext("experimental-webg