After quitting the game in the first run, having tried the first level for at least 20 times, I tried it again and with some luck I finally got it and then played through the other levels without a lot of issues.
I'm not sure how you've handled the movement, thus if everyone is experiencing the same game mechanics, but I've to agree with Geheim, the air movement is really non-intuitive. The acceleration horizontally is way too much. It's nearly impossible to make a one or two block jump without having to back steering. This is why the first level is so hard, the only way I managed to get through it, was by blindly jumping and hoping to hit one o the platforms, because it's impossible to jump on one platform at a time, as it's usually normal with platformers.
Well the forth level is kind of a joke and after it idiotically tried to jump up these stairs, which with the horizontal acceleration is impossible, I realized that one could just hit random keys and hope that one manages a mid-air jump at the start.
Let me know if you think, my movement isn't working as intended, then I could make a video to show it.