webglUtils.resizeCanvasToDisplaySize(gl.canvas);

    // Animate the rotation
    modelXRotationRadians += 1.2 * deltaTime;
    modelYRotationRadians += 0.7 * deltaTime;

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

    // Clear the canvas
    gl.clearColor(0, 0, 0, 0);
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

    // turn on depth testing
    gl.enable(gl.DEPTH_TEST);

    // tell webgl to cull faces
    gl.enable(gl.C