Great visuals with complimentary sound-effects.
I would have rated it a tiny higher if it had been a bit more original or unconventional.
But you know, some people don't care about that. They just want a good time,
and it seems you have succeeded in that. Kudos.
I got a bit confused about how to start the game though xD
I thought ENTER was the golden standard.

Finally: please tell me who made the animations/sprites. I may want to hire them

I was surprised by how short it was, then I read this was just a prototype.
It's a very much love-hate game, but I managed to beat all the levels : D

I suggest that you toss in some characters and dialogue between some levels,
to give people an incentive to push through the punishing gameplay : D
It would be outstanding if you added controller support for the final release

Best of luck!

I really like the art and presentation: it cuts right to the chase in a good way
without an overflow of pretentious boring dialogue that I often see in super indie games.
I really appreciate that. Would have been great though if you slowed down the
speed of the music arrow typing segments : D

Very professional and commercial sound. Great structure.
Good choice of instruments/plugins and notes

Pe-pe-pe-pe-pe-pe-pe-PENIZ

You have a good foundation, but there's very few instruments,
and those are all dark. I would suggest adding some lighter sounds
such as white noise, risers or pads etc