Wow, what a slick game, challenging, and devious!  I don't want to give spoilers, but the creativity and impressive gameplay gives this game more dimension than I was expecting.  Been playing over a week and still working on level 20, but completed 32.  I love the minimalist design keeping the focus on the action, and I rarely leave music on in games, yet this groove works for me (although sometimes it's beat doesn't match what I need to play, heh).  

One of those games you can get lost in, but crucial to not overdo if you see your performance dropping as you then practice/reinforce bad habits.  

Perfectly matches the psychological concept of "Flow", where you lose track of time.  This sounds like an over the top review, and I'm usually critical, but here we are, I obviously really like it.  :-)