I've been thinking about this recently. So far I have obvious stuff:

1. Chess pieces
2. Black and white
3. Squares and grids
4. Being literally the game Chess

But also more abstract stuff:

1. Moves being restricted by opponents' positioning
2. The need to "trap" an opponent to win
3. The need to think way too far ahead to be good at it

Not sure what I'm going to do yet, but I'm looking forward to it! ^^

There's a lot of obvious stuff (turn-based, variety of piece types with different movements etc) but something I really like is just how old the game is; it's literally ancient and every age we carry bits of it forward and in the end not everybody knows how or why things are the way they are, what different pieces represent or where they came from. It's basically some system of ancient magic we dig up and start screwing around with, hoping to master it (even tho realistically, it's probably beyond any of us as individuals).

I get the same feeling from a lot of other ancient games too tbh, we have rules and boards and pieces but who made them - witches? Probably.

I had an idea for something I wanted to make but your list of abstract properties of chess made me rethink that. What I have is just based on the very basic ruleset of chess.

But maybe I can incorporate them into my existing idea? Thanks for the thoughts.

If you want it to feel close to the original game, you could start with chess itself and do something that adds or removes restrictions to or from the core mechanics. Examples:

• Let players position their pieces before the match, possibly taking turns and being able to see each other's choices
  • Allow limited customization of how many of which piece a player can have
• Remove the restriction on pieces moving through each other
• Add something like the "king" mechanic in checkers to allow pieces to gain or change movement options
• Have board size variations to fundamentally change the game without changing the rules
• Instead of removing a piece from the board, switch its owner and put it where the piece that took it was

To me, the key feature of chess is the protection and attack of the king. That you lose the game when this single piece is trapped and cannot escape.

I do find chess magical just in how kind of perfected it is - in the sense that it contains so few simple rules and pieces that return so much complexity. It's basically what any puzzle game designer aims for, but as you say honed over literal ages. It's hard to imagine you would design it the way it is now if you were starting from scratch, but it just works.

Also, for all I said about abstract ideas of chessiness, I think I probably will end up with something mostly following the rules of chess. I think that's fine, as long as you're exploring something that you find interesting about it.

If a chessy  game is the same as a chess variant. I have a more simple way of defining it: A game is chessy when you some how can use chess skills to play it.