Sure, a lot of retro games, especially from the SNES: Super Metroid, LoZ AlttP, the Mario All Stas Collection.
But also like GBA games like Pokémon RomHacks or Mario vs Donkey Kong.
But I also really enjoy playing some Portmaster games. I actually spent most of my time now playing Shovel Knight lol. But I also have fun that Sonic fan games are easily installed. I played a bit the Sonic fan game Sonic Robo Blast 2
Problem solving is basically patent. After all what is stopping a megacorp from using the same solution but in such a way that doesn’t copy the exact work? Software for example, with current IP law, clean room reverse engineering is completely legal.
Think of how Tribute of Panem and Divergent almost have the exact same story beats but are still separate IP. IP protects singular works, like authors and their books, artists and their work.