"Things inside other things, doing things with stuff." is the basic recipe. Each thing has a timeline and a variety of ways to draw py-cairo graphics. Each Thing can contain other things, and so-on down. Things can be tweened around keys like size, rotation and alpha.
Inkscape is the 'extended' IDE for this API: You can draw all your vector graphics there and pull them out into Things via Python. You can draw individual 'sprites' or multiple 'loops' or paths and masks.
There is a (primitive) event system -- so you can do mouse stuff. Indeed there is a ButtonThing and a HitThing ready for use.
My hope is that someone (with a brain, not like mine :) ) will take this API and turn it into a fast C/C++ library. If this could happen then we could focus on building an actual IDE to draw SVG and code Python and layout keys all on a visual timeline. It could be a really neat animation system for GNU/Linux (and other platforms).