Late reply - but I ended up going into the GGJ solo for the first time to challenge myself - I wanted to see how many games I could make! Result was 4 games. They all support 2-8 players. It was fun presenting it, I hooked up 8 NES and SNES replica controllers and got a lot of audience participation.
http://globalgamejam.org/2017/games/ultimate-cat-drift-comet-bumpers-bananacontra The four games are Bananacontra, Ultimate Cat Drift, Comet Bumpers, and 'untitled secret tactics game'.
The graphics are rushed and anything but polished, but I decided to focus on quantity over quality this year. Still, I reckon it can be a lot of fun if you have a lot of controllers and friends lying around..
So, the idea is such: imagine a water sufrace. When you drop a pebble into it, the waves start spreading from the centre. Now let's look at this process from the opposite side: where should you drop the pebble to create the waves of particular shape? Taking into account that the waves reflect from the walls of the basin, this can be a very interesting question.
Wow, that's a fantastic idea General!