Metanet, developers of XBLA's N+, are hard at work on their next title, Robotology, and have been openly discussing their development hurdles at their blog, a refreshing level of transparency on the process. Central to their difficulties right now seems to be moving past sprites to animation in the 2D setting:
We don't have animation properly "sussed" yet, otherwise we'd be able to better explain what the various aspects of the problem are.. all we can say for sure is that once you eschew sprites, it gets tricky ;) Of course, this is the whole point — if you want to avoid the limitations of a sprite-based system, you're necessarily going to have to deal with all of the problems that using sprites lets you avoid.
In the same post, though, the Metanet guys reveal they've set up an expansive Etsy shop of N+-themed merchandise. Merchandise! If you like cuffs, there are all kinds featuring scenes from the game, and some good-looking ninja shirts too.