Ok, I feel I have to make this review, difficult though it is.
Aperture Tag is a feld of contradictions, and I really am not sure whether to reccomend it or not, and whether or not to review it as a mod, or as a paid-for game, whether I should compare it to Portal or view it as a standalone. And furthermore, I'm not sure if I should review this as the big Portal fan I am, or just as a general gamer.
As gameplay goes, it is fun, that much is easy to say, the makers obviously have a lot of experience with Portal on the workshop most likely, and each chamber is fairly well finished. The puzzles are challenging to an extent, which is as it should be, and only being able to use gels does give an interesting element to gameplay.
As many have said before me, it does fall down a bit in areas like cohesive-ness. The general storyline is 'Here are some tests, solve them' which isnt bad in and of itself, but the problem is this is based off Portal, something well known for its good story, and was one of the main things that made the two games memorable. Additionally, there isn't that much of the gameplay, it's about the same size as the first Portal game. When compared to its big brother, it doesnt stand up because it simply can't, this is a mod, made by a few fans, and it shows through in places like the story, and how the core that shows you around is fairly badly recorded, and basically has a one dimensional personality. The references to Portal 2, even putting you in a few chambers from the game, and how 'Nigel' is a bad mirror of Wheatley show how it is straining to live up to the original in ways it never can.
But I'm nit-picking this in ways that some of you may think is unfair, I shouldn't compare it to the game because it is just a mod etc. But the problem is this isn't just a mod, if it were I would say A+++, and be done with it. No, the thing is you have to pay for this, which makes it a product, which means you have the right to have your say because you're paying for it.
At the end of the day however I just need to review this, so here it is: I enjoyed it, it was fun, challenging tests, new gameplay idea, great soundtrack courtesy of the ever brilliant Harry Callaghan, and for me as a big Portal fan I don't really regret buying it.
Yes, at times it has the slightly unpolished feel of something that belongs on the steam workshop rather than the store, and yes the story falls down a lot, but it's fun, which is what a game should be.
So, if you are a fan of Portal, and you're willing to pay this much, I would reccomend you do. If you are looking for a cheap puzzle game to spend a few hours on (only a few mind), then again, reccomend it. But if you are hesitant, or not that big a fan of Portal, or not that prepared to spend money on a mod, I wouldn't, go spend it on something you're sure of.
TL;DR Fun, challenging puzzles, bad story, short play-time: If you're a portal/puzzling fan, reccomend buying, if you're not, wouldn't reccomend buying.