Build the board out of bricks and it's both stable amd you get easy access for bricking online!

What's a knook? A mix between knight and rook? How would it work?

Looking at the code adding another piece should be doable since I don’t think any pieces call other pieces attributes, and the pieces at game start are just objects in a list…

Adding the knook would be pretty simple actually. I'd just need to combine the code for the rook and the knight and then make a function to snap the mouse position to the right closest point on the crosshair shape.

This is true.

I've taken to asking players who are unfamiliar with the game if their familiar with it on occasion, at least ones who I expect will be more frustrated than amused.

It used to be a potential invitation for a fist-fight before we had pocket computers with which the aggrieved (and unaware) player could verify the move's legality.

Also true for some other little rules people often forget, like underpromotion, castling through/out of check, stalemate, perpetual, 50 moves, etc.

Plus the general topic of how to use clocks.

Chess is so popular that most people first learn to play from parents, relatives, etc., so they might not have learned the full rules if they aren't interested in learning the game more seriously.