So I was harping on about expanding Tumiki Fighters into a biological two-stick Katamari game, and had started a prototype demo, but it was all a bit shitty.
You'd start in a cell and the cell's nucleus would start attacking you by releasing antibodies which would shoot at you. If you got shot, parts of you would fall off, provided there were parts to destroy. If you shot the antibodies, they would die, and you could pick them up, at which point their weapon would become yours, and the camera would zoom out to compensate for your increased size. Picked up cells would crowd around the player's location - I eventually wanted to enclose these in some kind of physical mesh so it would look like an amoeba.
Now, once you get out of the cell (i.e. once you've defeated the nucleus), you realise that the cell you were in was just an antibody of an altogether larger cell with an altogether larger nucleus. These new antibodies/nucleus would be too big of course to attack so you'd have to penetrate the wall of one of the other large antibodies and take on the nucleus inside that.
The main problem occurred when you'd done several of these babies and you'd grown to perhaps 30 times your original size - your player would consist of hundreds of cells (I got rid of the tiniest ones) and things got really chaotic as the tiny bullets moved much more slowly than the larger ones.
Now, though, what I think what I'd do is for each antibody you destroy, you power up your existing weapon of the same type, up to a certain size dictated by how much you've absorbed up to this point. If your weapon is larger than this, it splits in to two, or evolves, or both or something, with an associated graphical change to help telegraph the exponential change in scale occurring over the course of the game. This way, instead of having a ton of tiny weapons you still get to have the absorption and evolution of different weapon types, but everything is contained in one (or a few) neat package(s).
Getting hit would reduce your size, and reduce your weapons accordingly.
As you progress through the game, different environments would be introduced to make it seem as though you were moving through different parts of the body and getting bigger all the time, so that at the start you are attacking cells as described and later you are attacking sphincters, minor organs, major organs, muscle groups etc. and finally the heart or brain. The game could be set inside an alien to facilitate fictional biological entities in much greater numbers than would normally exist in animals we know today.