Cool! I'm glad its still ongoing! I think the Tyranobuilder/Renpy community would love this product, being on steam would be awesome as well.
Hmm maybe mp4 doesn't support transparency. I just know that trying to do it frame by frame with a gif is tedious as heck!
A png sequence could work!
My goal is to use gifs/clips of looped poses for each emotion for my character's instead of stale 2d images. The transparency would let me use the same emotions no matter the scene.
Edit: for what it's worth I just bought it! Let me know if you ever need feedback :P