I have been working on creating a chess coach to help myself and players improve.

In particular, surfacing tactical concepts like pins, skewers, discovered attacks and forks in games proved to be tricky.

I have been testing out a few implementations and have some decent results for a first pass but also many learnings.

For example, to make a move that forks two others pieces is more beneficial (from a material gain perspective) when those pieces are unprotected or not protected well.

Yet in chess.com definitions page of a fork I see "A fork is a basic chess tactic that consists of a single piece attacking two or more pieces at the same time. The attacking piece is known as the forking piece, while the attacked troops are known as the forked pieces."

This definition is great but does not mention any concept of protection vs un-protection of pieces.

I mention this because to program rules around when a fork / tactics should be triggered was an interesting process.

See tactics being detected - https://imgur.com/a/detecting-tactics-bRdsY7u

You see images of forks, pins and discovered attacks from my own games.

If you want to try this out on your games, you are welcome to https://app.chesscoach.dev/