Shout out to Fishery (309 reviews). It’s pretty niche as an aquarium simulator, but very relaxing and well made.
Also, Ozymandias (770 reviews) is a great strategy game that manages to squeeze the feeling of a full game of civilization into less than one hour.
If you’re interested in classic board games, The Conquest of Go (397 reviews) is a great entry point into Go, with nice tutorial features and a campaign mode that scales difficulty as you win games.