[kriro]

As far as I know (IANAL) only the art and possibly the exact wording of things on cards can be protected. The actual game mechanisms can not. Magic the Gathering famously had (iirc. it expired in 2014) a patent on tapping (turning a card sideways) but you could still use that mechanism without calling it tapping (or using the tap-icon).

Basically you can clone any game if you remove all the flavour. The more you add, the dicier it may become. So having red, green and blue cards should be trivially ok. Naming the gnomes, dwarfs and humans should also be ok. more detail than that and it's thin ice.

Would love actual experience. I'm sort of cloning a board game as well (for personal use and AI research).

Love Terra Mystica, probably played on OP's site before buying the game :)