I found this "30 Weird Chess Algorithms: Elo World" video interesting, informative, and entertaining. And it features an Apple II by reference, and the NES too, so it just about has a 6502 relevance. There's a PDF version too, with different jokes.

Although there have been many efforts at chess programs for the 6502, some rather strong and some rather successful, most weak chess programs don't necessarily make a good chess partner for a weak human. I think it could be an interesting problem. There are a couple of suggestions in the comments to the video, including
- the strong player discards the queen first and then plays well
- the strong player accepts every offered capture and doesn't expose pieces but otherwise tries to play badly

(The NES connection is with the program Chessmaster, described in the paper like so: "A nice thing about this engine is that it is an earnest attempt at writing a good engine, but limited to the techniques of the 1980s, and running on hardware that was under-powered even for its day.")

One suggestion I made in the comments was to use a pseudo-random evaluation function (eg. based on the Zobrist hash of the position), and then to do a normal minimax search to a particular depth. This results in something called the Beal effect, which actually makes for a functional chess engine because it favours positions with lots of mobility for the engine, and less for the opponent. With enough search depth, it supposedly plateaus at about 2000 ELO, which is a fairly competent playing strength.

At one time anyway, the Fritz chess engine had a "tactical presents" mode, where the chess engine actively tried to get itself into reasonable-looking but tactically flawed positions. A light would light up on the board, indicating that a key tactical move was present.

Since this is a 6502 board, I will mention in passing that Colossus Chess 4, by Martin Bryant, was probably the strongest 6502 chess program of its day. It had a surprising number of modern features, including pondering.

The great grandaddy of all 6502 microcomputer chess programs is, of course, Microchess. https://en.wikipedia.org/wiki/Microchess