Great work. A few thoughts from the initial experience: I like the linked numbers design. As it reminded me of Bret Victor's work, I was expecting scrubbing to

Great work. A few thoughts from the initial experience: I like the linked numbers design. As it reminded me of Bret Victor's work, I was expecting scrubbing to work directly with numbers, which caused occasionally a bit of havoc, but I think you did a right choice of putting linking as the main action - touch design is hard. The free-form infinite layout gives a mindmap vibe: it's potentially great when you are trying to understand pieces of a problem that you need. The downside is that the canvas becomes a bit of mess quickly. The other alternative could be a Mathematica style, free-form document, with more restricted flow of equations (and text). Because the organization becomes a bit of problem, undo is a must and solves a bunch of other problems. I'd implement area selection of equations (initiate with long tap?) to quickly move things around. Y-axis could auto adjust by default or quick slider scrubbing should work directly for axis max-min values. You probably want a simple document model as this is something between calculator and full featured computation software. Maybe just save every canvas when user clears/starts new one All in all, great work!