Resonate is a new PSP Homebrew game where the objective is to evolve. You start as a Sea Urchin, and can move up to Tuna, then Stingray then Thresher Shark by collecting evolution tokens. But get damaged, and de-evolve into a lowly Plankton, or lose the level. As a rail shooter it is all about timing and aiming. This game is inspired by the PS2/DreamCast game Rez.
The game has not been released yet, but a video: https://www.youtube.com/watch?v=AKmvRmS4cAU