The Pico8 engine piqued my interest for this Jam and I ended up making 2 games for it. The first, a match 3 game, was made inside 24 hours, and was my first Pico8 game (and my first introduction to LUA), the second took another 10 days and had an incredible scope, incorporating a 500ly wide procedurally generated galaxy, a list of tradable commodities and an upgradable ship. Thankfully I decided against actually having a flight model (and essentially making Elite inside of a fortnight).
I quickly hit Pico8's memory limit with a galaxy 1,000 Ly wide, even when using PRNG Seeds to only generate planets when needed. Downsizing it to 500 Ly solved that problem though.
Challenging, certainly. I may also be legally insane too.