It's been many years since I've really done much that's directly game-related, but I've accumulated enough ideas over that period of time that I'd really like to play around with some of them to see if they're as much fun in practice as in theory and if they're worth doing anything more with, since I have plenty of free time at the moment. While I'm capable of putting together a basic engine/environment for testing things out in, I'd rather not waste too much time doing that and would prefer to take something already existing and modify it to meet my needs (if needed).
Ideally it would be something free, cross-platform, and reasonably well supported/documented. For the time being, I'm likely to be sticking to 2D stuff, and I suppose tile-based is the easiest way to go. Some of my ideas may get a bit hectic and action-y with a bunch of scaling/scrolling/rotating, so I'd go for a bit more complex but efficient over easy-to-use and slow if I have to.
I honestly have no idea where to start. I've written code in all sorts of languages for various purposes, from Fortran to Python, but the last time I did much graphical stuff, my OpenGL 1.2 book was considered up-to-date, so I'm not exactly up on what languages/libraries/frameworks/tools the kids are using for stuff like that these days. Heh.