Anyone here that makes games for fun or on the side?
A good platform that forces you to think small is pico-8, it's got all the tooling built in but it's on a very small screen and you're limited to something like 8K tokens of source code. But some of the games they've built in it are great, like Celeste.
I've tried a platformer (from a tutorial) and a Zelda-like game, but got stuck at some point so I should make something even smaller / simpler. Maybe that tunnel game mentioned in the OP, I used to love games like that. Oh, and the first game I made from a tutorial was like the 'helicopter game', single button, randomly generated levels, that kinda thing. Can be cobbled together in a matter of hours.