I wanted a strong aesthetic so went for a four-color palette of black (actually dark purple), red (blood), brown (bodies), and yellowish-white (bones, eyes).
For the mechanics, I came up all kinds of horrible things to happen to players. Eventually, I narrowed it down to people's severed heads being the balls the game is played with.
From there the basic rules crystallized - you can move around if you aren't holding the head, throw it around (with blood trailing), and score by throwing it through a hoop - that last bit being borrowed from the traditional Mayan ball game.
To make it interestingly hard to score, you also have to catch the ball again on the other side of the hoop. And of course if you have ball throwing you need intercepting throws, and tackling. And if someone gets killed, their head becomes the new "ball", which leads to some interesting tactics where you can kill your own player to get ball possession...
Speaking of ball possession, with the ball being a head, it too can get in on the action. Obviously, this being hell, the head remains conscious when ripped off the body. It can bite its carrier or scream horrible things to stun people nearby.
The implementation went fairly smoothly. I started out by drawing the pieces of art I would need, like the players and demons. The four-color scheme did pose some challenges when I needed to highlight things, but I think I succeeded. The two team colors are red (Team Blood) and white (Team Tears).
I did the basic rendering of the game board and fiddled around with its size and the tile size for a bit. Then I implemented the introduction sequence where the big demon goes and rips off one of the players' heads. Next, the basic actions like selecting players and moving them. I didn't bother with any clever pathing - players just move from one point to another without worrying who's in the way.
Tackling required a bit more: the tackled player has to have a free adjacent tile to be pushed into. And the intercept rule required some logic to see who had the chance to do the intercepts.
Once I added the win/loss conditions and stuff the game was playable but still a bit dry. I had a few hours left so I hacked in some really basic animations using linear interpolation, a particle system that only supports red particles, and some quick SFX which I recorded in a single take at 1 AM.
All in all I'm pleased with the way I created a coherent aesthetic and an actually quite deep strategic game in a single day. Of course it being a hotseat game will severely limit its appeal, but there was no way I could have written an AI for this within the time available to me. I hope some people do find the time to find another player and play it properly.