I usually don't write reviews in English, but I feel like it could be useful to some, so here we go.
Unlike the other reviewers (judging by the hours they've put into it), I've actually beaten the game. So you can believe me when I tell you it's tough. Really tough. The difficulty is fairly reasonable in the first zone, but from the second zone onwards, your patience is going to be tested a lot. So if you're easily frustrated, skip the rest of this review and go find another game, because you're going to pull your hair out until you're hairless in every zone of your body. Hell, you might pull someone else's hair out too.
But anyway, first things first: the gameplay. The main concept of Volt is fairly simple: you're a battery, and your goal is to escape from a factory, so you can live in freedom rather than being destroyed. This is easier said than done, however, because you can't walk. All you can do is swing (using a limited supply of electricity beams) and jump (using a very limited supply of energy). Some variations and complications are introduced in the game, but most of the time, you're going to be swinging through a level and solving platforming puzzles. And I must say it mostly works quite well. The swinging and puzzle-solving is entertaining, it is implemented in a variety of ways to avoid being repetitive (across different levels at least), and it has some nice highlights in it. The boss fights, for example, are well done and pretty memorable.
But the gameplay isn't Volt's only strong point. In fact, if you ask me, it is not even its strongest point: that prize goes to its atmosphere. It probably doesn't suit everyone's taste, but I really like the minimalistic, high-contrast industrial environments, and I really like the music as well. It varies between ambient and minimalistic techno or trance (whatever you wish to call it), which fits the visual design of the levels really well and sets the right tone for the game. I personally preferred the more energetic music from zone 3 onwards (as it makes for a more uplifting atmosphere), but the ambient was pretty great as well.
Unfortunately, however, even though Volt is, in my view, a good game, it is far from perfect. Most crucially, it can become very frustrating at times. The levels have no checkpoints, and they are pretty long (in comparison to Super Meat Boy, say), so there are plenty of levels you're going to have to spend a long time in before finally beating them (over half an hour). Add to that imprecise controls (as is to be expected given the physics-based gameplay, but better design might have alleviated the frustrations a bit) and some questionable level design (a puzzle on the end of a difficult long level, where you will inevitably die a couple of times), and the result is that unless you're some kind of Buddha, you're going to cry in agony multiple times.
All in all, I do recommend Volt to some gamers, but I certainly don't recommend it to everyone. If the main concept appeals to you, if the atmosphere suits your sentiments and if you like a challenge, you could do worse than buying Volt. It's very cheap, after all, and it offers about 15 hours of gameplay (although it must be noted that you're going to be stuck in the same levels a lot of the time, making the game pretty repetitive at times). If you're easily frustrated, however, you should avoid this game at all costs. 7/10