Patrick's Parabox
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[0]: http://sigbovik.org/
I'm quite far in now, but I think there's still a while to go. The game purportedly had 300+ puzzles.
More than anything I'm really enjoying how comprehensively the rules are explored. There seems to be every permutation of rules used in a puzzle somewhere and the number of different 'rules' or 'ideas' that it gets out of a relatively simple premise is pretty staggering - probably more than most sokoban games I've played.
On that note, I'm really enjoying the glut of quality puzzle games recently. The Witness, Stephen's Sausage Roll, anything by Alan Hezelden (Good Snowman, Cosmic Express, monsters expedition), Bonfire Peaks, Pipe Push Paradise, Baba is You, Recursed and more. It's a good time to be a puzzle gamer.
All the games above came out in the last 7 years, use modern technologies and are available on modern platforms. I'd contrast that to older puzzle games that need special compatibility tools to get running (Myst) or haven't been updated to modern resolutions or other devices like touch or controller support (e.g. Braid).
Another sokoban game with a twist: https://store.steampowered.com/app/316610/A_Good_Snowman_Is_...
EDIT: Apparently when you exit the side of the level with your character, they appear on that side of the "level" block you are pushing around.
* Stephen's Sausage Roll
* Bonfire Peaks
* Baba Is You
* Sokobond
* A Good Snowman is Hard to Find
I’ve pretty much soured on trying new games several times over the last decade, only to be delighted by a new game or class of games which tickle some niche fancy for me. Given this and some of the other recommendations in these comments, it looks like I’ll be starting another iteration.