I'm playing Ori and the Will of the Wisps. It has a 90% discount in Steam right now and it's been on my wishlist for a long time.

It's a beautiful game to look at. It runs great on the Steam Deck. The only issue I had was that it's quite dark for the OLED screen, but I've turned up the brightness and now it's good.

I find it quite challenging to play though, but that's part of the fun. If you like metroidvania games, I do recommend it, especially at its current price.