It is illegal to make a "demake" of a video game?

Question

Let's say about a "demake" of Artifact (Valve's card game).

The new game would be a "generic" Artifact that doesn't use the lore, characters, and other protected things, but uses the same concepts

The new game would have the same exact amount/number of cards from Artifact, but all cards would be renamed (these cards would also retain their mechanics and abilities). The game would also retain the gameplay style (players competing into three separate boards) and UI layout (with a few changes).

Would this infringe on Valve's IP (in this case)?

Answer 1

Game rules can't be copyrighted.

I am not a lawyer, but it's my understanding that game rules can't be copyrighted, merely particular expressions of them. That's why it's legal to make retroclones of old editions of Dungeons and Dragons- as long as you use different words to explain the same rules, you're fine.

In the case of a video game, I think that would mean that as long as you don't reuse any of their code, game assets, or other creative aspects (characters, setting, etc), and you use your own wording to explain the rules, you should be fine.

You'd also run the risk of trademark infringement if your Artifact clone could be confused with Valve's product by consumers, or if consumers might think your product was authorised by Valve somehow, though.