The tool I'm using is actually closer to a programming tool, it doesn't have "Sprite importer" so much as commands to create them myself. Here is how a Sprite sheet image, previously loaded with a command, could be created into a Sprite for example:
As you can see the engine has this primitive charm to it. It expects all the animation to just be frames scattered over sheets. It also expects the user to code just about everything, the tool itself is a basic language sdk more then anything visual. It just happens to be hooked up to a very efficient renderer/processor capable of some sweet graphical outputs with a lot of under the hood work done for the user already.
I am actually making a little level editor using said tool, with a Sprite blitting itself around the screen to create the tiles of the game. So then I just call a draw tile function and let the single Sprite do its thing. It is very similar to old school game engines in that regard. I find it fun to use, though many others would probably be like "why?". Sometimes such limits are what keep me going. I like taking silly limits and really pushing it. :)
I will look forward to the update!