I had a lot of ideas for games, but didn't really like any of them. A few were sort of decent and obvious, like :
1. Make a game where your play creates a song. Basically different user actions or environmental objects create certain sounds or turn on different tracks. By playing the game correctly you make a cool song. The true "synesthesia" moment of brilliance would come if you could play either by just doing the visual gameplay things, OR purely by closing your eyes and trying to create a cool song, and if you create a cool song that also beats the shooter/platformer/whatever.
2. Make a game with sound input where doing the gameplay causes you to make sounds that are cool and/or feel like the play. The way I was thinking was similar to #1, for example you could make a "beat boxing platformer" where different beats make you jump or duck or whatever, then the level sends things at you and you wind up making a sound track by playing. Casey had a really cool idea for a variant on #2 but I won't out it here, hopefully he'll actually finish the game and it will be cool to play.
Anyway, maybe I shoulda done something like those, but they just felt like the same old game. Most video games feel like a series of rote/mindless tasks that are presented to the user in sequence. I'm sick of making those and playing those, and this was really just another of those in different garb.
So, I tried to play with some toys that would feel like different experiences, and mostly failed. On the plus side, now I know my arm is okay to type again, though I was irritating it quite a bit.