Well, that was probably the most engrossed I've been in a game for a while. It takes me right back to "Driller" or its sequel "Far Side" which, used "Freescape", an early 3D, to evoke alien and unusual environments. Unlike those two early games, Kairo gives no backstory, and lets you attempt to figure it out for yourself. I love it...
The whole game is extremely minimalist in its level design, but extremely evocative of space and alienness. The aesthetics are a mix of old and new: blocky, simplistic but with texture mapping, reflections, fog, flames and more. The overly simplistic design may deter some who would dismiss the game as dated, but anything more complex would start to get in the way of the narrative.
It may not have been the designer's "point", but the simplicity of the environment allows you to completely ignore it, and focus more on playing the game. And playing may not be the best definition either: experience, discover, enjoy are also great definitions for this.
The beginning makes it look like you'll be exploring ancient egyptian ruins (albeit in a dreamy world of whiteness), before abruptly turning grey and industrial-feeling. The game continues to take turns and each area feels and plays a lot different.
The only time that the simplicity works against the game is when an area is more complex than it looks. After traversing a dozen empty corridors, and passing stray cubes, you may not realise that another grey unmarked stray cube is, in fact, a trigger for some action, and be left puzzling for a while. Such "difficulty through obscurity" is a hard one to balance right, to be honest, so I'll let it off, mostly.
I think the thing I enjoy most about Kairo is that it really plays with our preconceptions of what a 3d puzzle game is. They jokingly call one of their achievements "Locked Door Puzzle" as a nod to other more mainstream games.
I really enjoyed playing Kairo, and then with the help of a cheat to find all the secrets.. A great minimal game. If you do decide to play it, don't try and speed-run it. although it looks shallow and simplistic, there are a lot of hidden (or just obscure) tidbits for the explorer.