on;
          vColor = aVertexColor;
        }
      `;

      const fsSource = `
        varying lowp vec4 vColor;

        void main(void) {
          gl_FragColor = vColor;
        }
      `;

      const shaderProgram = initShaderProgram(gl, vsSource, fsSource)

      const programInfo = {
        program: shaderProgram,
        attribLocations: {
          vertexPosition: gl.getAttribLocation(shaderProgram, 'aVertexPosition'),
          vertexColor: gl.getAttribLocation(shaderProgram, 'aVertexColor'),
