Hello, With no small push from Andreas (and Pharo in general), I have been able to build something that is pretty much exactly what I envisioned. That attached has some identifiers blocked out but hopefully conveys what I am trying to do. The draw/erase and square/circle buttons do what you would expect, and apply to a monochrome mask that is represented by the dotted pattern. The next step is to integrate this into a larger shell, and this is where either I have something to learn of Polymorph has room to grow. What you see should be (in Dolphin parlance) a CompositePresenter that can readily be embedded in other morphs/presenters/whatever-we-call-them. As it is, I get a jumbled mess unless I create this in a system or standard window :( The images naturally come in three interlaced sequences of pairs. It would be very natural to show multiple instances of this composite structure. Is there a way to re-use it w/o a shell? Bill