I think it's a bit of a grey area, you can't patent abstract things like rules of a game, but a game engine makes that a little less abstract and turns it into

I think it's a bit of a grey area, you can't patent abstract things like rules of a game, but a game engine makes that a little less abstract and turns it into an implementation. For example, Magic: The Gathering has a patent here on the gameplay process: https://patents.google.com/patent/US5662332A/en https://patents.google.com/patent/US5662332A/en