I am wondering the same thing
Yes, you can use pico-8
From the FAQ:
What engine or programming language can I use?
Any engine or programming language is allowed. Jam games which are playable on the website are played more often, so you might want to make sure your engine outputs HTML5, but it's not a requirement.
What engine or programming language can I use?
Any engine or programming language is allowed. Jam games which are playable on the website are played more often, so you might want to make sure your engine outputs HTML5, but it's not a requirement.
You may use a smaller resolution if your game engine of choice does not produce 160x144. The play area should fit within a gameboy screen. Black bars or 'super gameboy' frames around the outside of the gameplay area are fine.