Nested

I found this game because it was linked in another game called The end of the WORD as we know it, which was an art gallery of sorts. I thought, "Wait, isn't Nested made by the guy who did Cookie Clicker?" and I was right. He's made other things too, but I don't think any of it will ever exceed the popularity of Cookie Clicker.

Cookie Clicker probably doesn't qualify for IF at this point, though, while Nested does. It's a quite fascinating game, though "game" might be a disputed term since there's not much to do besides look at things. It reminds me of the procedural world generation found in Dwarf Fortress, but where Dwarf Fortress has a lot of game mechanics attached to the procedural generation, this game is nothing but the procedural generation. The procedural generation is the only point, and boy is there a lot of it. You start with a universe, but you can zoom in to galactic superclusters and star systems and planets and countries on those planets and cities in those countries containing houses containing aliens wearing leather cloaks and the skin cells in those cloaks which are made of atoms which contain quarks which contain inside them pathways to other universes... The overall effect is one of overwhelming scale.

It reminded me of this "Metric Paper" video by CGPGrey, which similarly zooms in and out of our own universe. Mindbending.