I enjoyed the Witness to a degree.

* spoiler *

I did not notice the environmental puzzles, even after the obvious one at the top of the mountain looking down. I didn't get that that wasn't a one off. Someone had to point them out. I've had other friends who also missed that. It's arguably the game's single biggest reveal / surprise. It was pretty amazing!

That said, only found maybe 20 of them and was not compelled to keep looking for all of the rest.