For me Mutatzione[0] was incredible and appeared at a time in my life where I was in a very dark place. I discovered one saturday morning, bought it and played it the whole day. It's short, it's sweet, the art is beautiful. It's not super cozy in the traditional sense, but it has a lot of calm, serenity and it was exactly what I needed that day.

[0] https://store.steampowered.com/app/1080750/Mutazione/

That’s such a cool game. I also really like the sandbox music gardens. You might also like Melody of Moominvalley if you’re open to Moomin content