Beat the two middle ones on impossible, can't do the first and last ones with this cramped control scheme and a laptop keyboard.
Used to play quite a lot of keyboard (too) StepMania back in the day. My biggest issue here was the up/down mixup and how you punish for mashing on a completely empty space. I wanna do warmup waves at the start of songs to get into the groove! :D
The first and last songs featured a whole lot of double note steps one after another too which I never was too awesome at. I was more into super speedy single note chains. And I wasn't the biggest of fans of your song selection either.
Sometimes (quite often, almost half of the times) when restarting a song the beginning notes didn't appear at all. I don't think this happened when changing songs though, only for straight up restarts.
And then the UI, it wasn't too user friendly. Too many clicks needed to do anything and that's it, clicks! This is keyboard controlled game so needing to use mouse for menuing between tries (which can be very small duration) is annoying. The game also seemed to forget the high scores when changing songs.
Anyways, good job!