We have a FAQ channel in our Discord server, in that chat it says:
"This is a jam where you take a pre-existing game, and fit it in the style of a retro console! It's all about getting creative, or being more unique than just changing the colour palette. You could remake a pre-existing game, such as Portal, and place it in a SNES console's style, making it 2d, or redesigning some levels. You should not only convert the game into a different style, but also add some of your own stuff! You don't have to strictly stick to the limitations of the console, or the limitations of your game, but if you have the main idea there, and it is recognizable enough, then you're set!"
Hope this helps!