text: // MATRIX VERTEX SHADER
  
  var matrix_vertex_shader = `attribute vec3 aVertexPosition;
  			    attribute vec3 aVertexColor;
  
  			    uniform mat4 model;
  			    uniform mat4 pv;
  
  			    varying highp vec4 vColor;
  
  			    void main(void) {
  				gl_Position = pv * model * vec4(aVertexPosition, 1.0);
  				vColor = vec4(aVertexColor, 1.0);
  			    }`;
  