When the lenses overlap, their operations compose. That is, the colors become both darker and yellowish. Changing the overlap order changes the effect of composing the lenses. Depending on your color display, this may be a subtle effect. Changing the Scene Move or rotate the polygons by dragging them with the mouse.
Polygons rotate if grabbed near the vertices, translate if they are grabbed near the center.
Lenses do not rotate. Any sequence of points is a valid polygon. To work properly, the lenses must be convex polygons. That is, they cannot have any indentations in their outline.