Since everyone’s mentioned the standards.

I’ve really enjoyed playing Tails of Iron (metroidvania with a focus on learning bosses attacks) lately. For programming games, I really liked Shenzhen IO (You create hardware with something resembling an Assembly language and a printable manual) and Human Resources Machine (drag and drop assembly programming)

I also have a soft spot for anything from Ska Studios (I maed a game with zombies in it, salt and sanctuary, salt and sacrifice, dishwasher, Charlie murder, and a bunch of older games that are probably not playable anymore)

Also looks like everyone else forgot to mention the great game that is Undertale as well.