Absolutely no feeling like playing this game and beating it for the first time. Antichamber feels like the father of all non-Euclidean/spatial puzzle games, it's honest genius and it blows my mind that it doesn't have higher renown or acclaim. I easily lost myself for days at a time playing this game, pushing past the motion sickness because it was just that good. The way it's constructed is unbelievably clever and forgiving enough to let you solve problems in your own way, as long as you know why you're doing it that way; essentially, it rewards you for understanding the systems and mechanics at play, rather than for finding the one 'correct' answer, as is the case with many puzzle games. Even though I'm normally much more drawn to narratively-focused games and struggle with more barren or simplistic atmospheres, Antichamber despite having no dialogue or characters still had something profound and human about it that felt in many ways more personal and intimate than a lot of narrative-focused games I've played; like it was a direct interfacing and conversation between the game and the player. In that way it doesn't feel lonely, because you are engaged with the game in a meaningful way the whole time.The climax/ending also made me feel genuinely emotional, even though it was still mostly a game about using boxes in your gun to solve spatial puzzles; the soundtrack, the pacing and sense of urgency that it created, the knowledge you've accumulated over hours of gameplay becoming second nature; all of it culminated in something that honestly felt transcendent.
I was never bored once playing this game. The gradual introduction of tools to your belt as the game progresses is always perfectly timed and only serves to pull you in deeper; what seems daunting or impossible at first becomes a well-worn and familiar path that you've tread a thousand times by the time the game's over. It's a game that rewards engaging with it and thinking carefully about your options; there were so many moments during times I was stuck on puzzles where I'd think 'that's stupid, there's no way that would work' in relation to a possible solution, only to then try it anyway and find it got me past the obstacle. The game's 'hints' too are just cryptic enough to push you in the right direction or open you up to a new way of thinking that'll lead you to the answer, without ever feeling like it's just giving you the answer on a plate. More importantly they serve to motivate you to keep going, which is arguably more important than any concrete hints to progression.
If you don't like spatial/outside-the-box thinking kind of puzzles, you might not like Antichamber (though I'd still recommend trying it anyway), but if you enjoyed Portal or Superliminal, you almost certainly will. Antichamber is less narratively focused than those games through humour or character, but what it does give you is hours and hours of raw complex interwoven puzzling that feels impossible to pull yourself away from, because every answer will push you closer to another answer. Genuinely a masterpiece.