Throwing out an idea for a game jam: set a limit on how much power (wattage) the game may consume when you play it. I mean total of CPU, RAM and GPU. There are software out there to measure this (the info is even available in task-manager on Windows and process analyzer on MacOS). Prove you meet the restriction by posting a screenshot of power consumption of for example MS Word (or equivalent) and your game.
What do you think?