Variant idea: Football Chess
ok this sounds insane and complex, but once you start playing it it's super fun and whimsical. Inspired by the recent world cup :)
there's a ball that is placed at random in one of the center 4 squares. The basic mechanic is: if a piece lands on the ball, the ball travels in the same direction and distance that the piece just travelled to.
The objective is to score a goal, checkmate is not a thing and you can capture the king (more on that later). The goals are on A6 and h3. Nobody can ever put a piece directly on the goal square, you should defend it by placing pieces around it.
So if a bishop hits the ball, and it travelled 2 squares to do so, then the ball travels 2 squares in the same direction the bishop just did.
When a knight hits it, the ball tries to "repeat" the same L movement to reach the target square. But because there are 2 different ways of reaching the same square with an L you get to decide which L the ball takes. It's like giving the ball spin.
If a ball hits a piece it cannot travel any further and it stops. If it hits the edge of the board it bounces off (so it can never get stuck on the rim).
Obviously because it's football we're talking about if you tackle an opponent (capture) instead of going for the ball, you get a yellow card. After two bad tackles it's red and your piece is out. If you tackle the keeper (king) it's a direct red card.
To add even more madness there are substitutions. You can substitute any piece out and your bench is a pawn, a knight and a bishop. You may play the same turn you subbed in a player. So if you really need a bishop to hit the ball and instead you have a knight, you can sub the knight out and hit the ball with a fresh bishop. Or, if a pawn is already on a yellow card and you want to keep it, you can sub another pawn in, and capture again. Subbed pawns can jump two squares even if they're in the middle of the board, as they're fresh players.
You can play on a board (you just need a ball cut out, goals, yellow and red cards) and that's also very fun. Or you can test a demo if you google "chess laboratory". It's like the third more popular variant on the main page.
That's it!
As I said, it sounds confusing and chaotic, and it is. But my goodness it's so whacky and fun.