Noita!: I agree with many in dubbing it my favorite single player game.
It is a pixel art alechemy and magic roguelike where every pixel is physically simulated and destroyable. Find spells and wands and combine them in programmer like ways to multiply their power. Many tricks in the game are so strong they feel like cheating, but the game has been built with challenges that surpass every trick.
It is the epitome of endlessly repayable. Especially switching between the few mods that drastically change the map.
I can easily have a god run last me 5-10 hours. But I still have a lot of fun with the more common 30min-2hr runs.