- 80's retro McCLIM user interface.
- No documentation or online help.
- Maximally frustrating color sliders, using IHS colorspace.
- Intuitive modeless drawing UI, achieved by including only a pencil tool.
- Saves/loads files only in its own format, based on unportable s-expressions.
- Requires X11 and SBCL with threads, to keep out the riffraff.
- User-editable brush shape.
- Remap Color and Silhouette commands, for tracing previous frames.
- Realtime animated preview plays while you work.
Update: I've added the ability to export an animated GIF file, using Xach Beane's Skippy library. Here's the "turtle.anim" example file, exported as a GIF: