anchor.diff:      buffer('a_Position', positions, 2);
       buffer('a_Color', colors, 4);
   
  +    var modelMatrix = createModelMatrix(tm, pm);
  +    var uModelMatrix = gl.getUniformLocation(program, 'uModelMatrix');
  +    gl.uniformMatrix4fv(uModelMatrix, false, modelMatrix.storage);
  +
       gl.drawArrays(RenderingContext.POINTS, 0, length);
     }
   
  
positive.code:     buffer('a_Position', positions, 2);
      buffer('a_Color', colors, 4);
  
      gl.drawArrays(RenderingContext.TRIANGLES, 0, length * 3);
    }
  
  
negative.code: }
  
  class BackgroundDotRenderingSystem extends WebGlRenderingSystem {
    TagManager tm;
    Mapper<Position> pm;
    Mapper<Color> cm;
    Mapper<Background> bm;
  