This is delightful: https://wasm4.org/
It’s a retro-ish “console” similar to the Game Boy, except that it does not emulate actual hardware; it’s pure software.
You write a game using a modern language that compiles to WebAssembly. The resulting .wasm file is your ROM.
There are already a few dozen classics rewritten for this platform, which you can play in your browser: https://wasm4.org/play/
A generalist Mastodon instance with a nice domain name. Running on Glitch Social's fork with a custom theme!