anchor.diff:    _gl.useProgram(shaderProgram);
     
     
  -  // logs of compiled status
  +  // logs of compiled & link status
     if (!_gl.getShaderParameter(vertexShader, wgl.RenderingContext.COMPILE_STATUS)) { 
       print(_gl.getShaderInfoLog(vertexShader));
     }
  
positive.code:   vpWidth = glCanvas.width;
    vpHeight = glCanvas.height;
    
    _gl = glCanvas.getContext("experimental-webgl");
    _gl.enable(wgl.RenderingContext.DEPTH_TEST);
    
    _initVertexBuffer();
  
negative.code:   double angle1 = radians(rot_y);
    worldMatrix.rotateY(angle1);
    
    cameraMatrix = makeViewMatrix(new Vector3(0.0, 5.0, 8.0), new Vector3.zero(), new Vector3(0.0, 1.0, 0.0));
    
    // set matrix uniforms.
    Float32List mat = new Float32List(16);
    
    // pass matrices to shader variable
    worldMatrix.copyIntoArray(mat);
    _gl.uniformMatrix4fv(worldMatrixLoc, false, mat);
    
  