').innerHTML = 'WebGL 2 is not available.  See <a href="https://www.khronos.org/webgl/wiki/Getting_a_WebGL_Implementation">How to get a WebGL 2 implementation</a>';
            return;
        }

        // -- Init program
        var program = createProgram(gl, getShaderSource('vs'), getShaderSource('fs'));
        gl.useProgram(program);

        // -- Init Buffer
        var vertexPosBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, vertexPosBuffer);
        var vertexCount = 12;
       