I want to show you what I'm working on. I describe my game later, now I'll just show some "engine-tests" (that is what game will look like):
http://www.youtube.com/watch?v=Xr39VE-V3Cw
http://www.youtube.com/watch?v=jVNGL--NmSw
http://www.youtube.com/watch?v=tJTgiSQeIMA
And some screenshot
The engine reaches 30-40 FPS on Celeron 1GHz with GeForce 2MX with almost full gfx details. So I think the game will be playable on such old machines.