Love it. The tone is just right. A couple of suggestions:

Have you tried a "filled line" approach, rather than "outlined" strokes? Might feel more like individual marker strokes.

I made a demo video on the free tier and it did a great job explaining acoustic delay lines in an accessible fashion, after feeding it a catalog PDF with an overview of the historical artefact and photography of an example unit. Unfortunately the service invented its own idea of what the artefact looked like. Could you offer a storyboard view and let users erase the incorrect parts and sketch their own shapes? Or split the drawing up into logical elements and the user could redraw them as needed, which would then be reused where that element is used in other frames?

Thank you!! We are actually currently working on the storyboarding feature!!