A Yume Nikki Fangame Jam. Not the big one like Dream Diary Jam, still a thing though.
The rules? are simple.

-you will have a week to make a ynfg OR an update to your previous work

-there are 2 days after the end that allow people to finish it up and publish, if need  be

-minimum requirements are 6 worlds, 1 effect

of course no stealing assets,as that should be obvious