If you can't be bothered to pay for Pico8, then try out TIC, it is essentially the same thing, slightly different, but not much. https://nesbox.itch.io/tic

Don't forget LÖVE (http://love2d.org). It's what I'll probably be using if I can manage to get off the couch enough to do any dev this month. It's more a framework than an engine (which is also the case for PICO-8/TIC) but it's pretty easy to learn and has a lot of great packages available for it.