I liked this a lot, not only how challenging it is but how simple the gimmick is (funnily enough, I had a similar project back then that I never finished, so maybe that's why I got used to it so quickly). Visuals are great and if the music was composed specifically for this game, you gotta release them, asaaap.
Also stage 9 is peak. (but perhaps for the majority, swap 9 with 10 for the proper difficulty curve).