Not sure I got the deal with the "inverted" controls (which according to the game are not inverted). I immediately "inverted" the controls in the options.
On the first level your buddy gets killed -- but when people die, they don't really die, apparently -- their "astral" projection (or whatever) gets kicked out of the psychic world. Maybe this is meant to make the player less afraid of dying? The developer was clearly trying to suggest something to the player here.
The checkpoints feel nicely balanced. Just before a hard obstacle, the checkpoint is saved. And after a difficult obstacle, a few easier challenges are presented -- followed by another checkpoint. This seems to be a repeating pattern which works.
Some parts of the level are very dark, which can make the game extra hard if you're not playing in total darkness (I had the blinds open on the window). This sort of thing would make the game quite unbalanced on devices where you can't predict lighting (e.g. phones).
Swinging on the bars: This obstacle was too tricky to be enjoyable I think. After a few attempts, you realise that the solution is to get to the highest bar possible, then rotate on the bar and go the other way. I felt that the controls to rotate the player were not that intuitive -- the "F" key!? The same fucking key as is used to talk? Seriously? So that spoilt the experience a little. I also saw some guy on YouTube have this same stumbling block, so I assume it's not just me being a dumb ass. An on screen hint reminding you how to rotate (after a few attempts) would have solved this problem I bet.
Got a little bored looking for that Sasha guy (though this is only level 4 of 13) -- but I might pick this review up again later.