I had breakfast, it was mostly toast. I would have posted an image, but you can just check out all the others, and you’ll get a good idea. Though there was a cupcake too. Nom nom.
Anyway, some ideas
You use an advancing wall of doom to crush cities. This could either be a puzzle game (use your wall in the most optimal way!), some sort of RTS (gather resources etc, expand your wall), or RPG-like, you only actually control one character, but it’ll need to go out and gather power to advance the wall. Or something.
Also had the idea of not crushing cities, but rather have two elements that fight, one being for example a jungle and another the desert. The edge would be the ‘wall’, and both strive to doom the other. Would probably work best as some sort of RTS.
Then there’s of course the tower defense sort of thing, but it’d be wall defense. Could sort of work from either side — either you build the wall (wall defense!), or you need to defend against the wall.
And there’s a lot of ‘run away from the wall’ kind of games, but I’m not interested in those because I don’t usually find that kind of games fun.
Don’t yet know what I’ll do, the RTS ones sounds most fun, but would probably require a little bit too much work. So I’ll ponder some more.