Hi Graeme, nice game! Suggestions:
- I find it often that I get stuck in an endless loop, like a pawn chasing a knight in a loop. I have never played Chess before, but I think endless loop can happen? It would be frustrating if the player has to give up, or if the AI gives up, it would be less rewarding. So I think maybe you can implement some mechanics to prevent this. Maybe somehow not allowing repeating moves, maybe have some environmental events after a while(setting areas on fire, meteorite strikes, board shrinking, etc.).
- Having a fast mode would be a nice feature. I mean in some games like Civ 6, there is an option to shorten or skip animations.