code: function MatrixStack () {
  
      // # Gl-Matrix inheritance
      // Create inheritance if not already created.
      // Doing it on first initialisation so that `gl-matrix`
      // is not require just to load W.js on node
      if ( typeof MatrixStack.prototype.glMatrix === 'undefined' ) {
          // Extend gl-matrix as in browser it is global, in node it is a module
          if (typeof module !== 'undefined' && module.exports) {
              // NPM
              W.extend( MatrixStack.prototype, require( 'gl-matrix' ) );
          } else {
              // re-wrap in browser
              W.extend( MatrixStack.prototype, {
                  glMatrix : glMatrix,
                  mat2 : mat2,
                  mat2d : mat2d,
                  mat3 : mat3,
                  mat4 : mat4,
                  quat : quat,
                  vec2 : vec2,
                  vec3 : vec3,
                  vec4 : vec4
              });
          }
      }
  
      this.stack = [ this.mat4.create() ];
      
  }
docs: Requires 'gl-matrix' http://glmatrix.net # Class