This will make for an excellent HN post once people can actually try it. Landing pages with email signups aren't a great fit for this site, though this is an impressive one.
I wish something like this existed as a desktop app to output animation spritesheets from drawings.<p>The only application that works on Mac OS that does that is Flash. You can draw something, make it "tween" to a new position/rotation/size etc and output .pngs.
Looks pretty sweet. I can't see much use case for it though to be honest. Animation's while reading is distracting, but maybe it could be useful for some interactive tutorial.
So you can export as GIFs? That would be cool, but I am skeptic.<p>LE: I say this because the animations on the site are gifs, and I assumed that they were made with spiritjs itself.
This is so excellent and looks fun. I'm really unconfident with my web animating abilities, and I feel I can learn a lot from this project! Thanks!