Great game! I really like how the music is in sync with the moving blocks, makes it enjoyable and you want to go further to hear the rest of the song. ;)
One thing though: Sometimes i feel like the gap(between the upper and lower block) is too far away from the next gap, making it near impossible to not hit the blocks. I feel like i would have to know three gaps before that this gap is as high, just to time my keyboard pushes.
Are you even sure that it is always possible... with the trajectory of the square... to get through the gap?

Amazing game. I love this because of the music and the Flappy Bird reference. Mine never lagged, and I found this brilliant! 5/5, Seriously- P.S Make something like Super Hexagon.

Hm... Fix the lag previously mentioned and call it a day... But know what? Try not making it like Flappy Bird. It's bad for development profile.

It seems like a good concept, but it lags at certain points.