TIC-80 isn't quite as refined as PICO-8 but its still pretty awesome. A few months ago I figured out how to setup TIC-80 so I could code on my mobile whilst on the move: https://www.youtube.com/watch?v=FxQpRoZI3kM

Absolutely love TIC-80. Definitely worth paying for the pro version even though you could just compile it from source if you want.

There's also Pyxel: https://github.com/kitao/pyxel

Similar, but no paid version at all, and you can write as much Python as you want.