!!! Creating 2D animation for games
One way to ease the creation of 2D animations would be to make it Skeletton based (or puppet-based if you think of those cardboard puppet).

I'd like to make text-based interface like vi, so that it's useful on a BlackBerry

Should I try Blender? It already offers animation support and is 3D based.

The basic interaction idea is to pull one item, others follow. Then additional rules/features can be added:
* The should be constraints for movements (rotation at joint, translation of a point of the segment)
*Joints need some behaviour (locked at angle, loose) that way one can adjust multiple segments in one go but keep existing adjustments.
*Interpolation is useful. Only need to define key positions to get smooth animations

The rendering could be as a skeletton (segments), surfaces (polygons,ovals) or textured polygons