i am a huge fan of rhythm games and really like this idea! it's scratching my "how do i do this," rub your belly and pat your head at the same time brain in a way i really like.
my only criticism is that the sound effects actually detract from the music a bit. i know it should be a reward, when you get a perfect the sound effects line up. unfortunately in practice, especially when you're sightreading a chart, the sound effects start becoming a distraction from what's happening in the audio. it almost causes a bit of a spiral effect where you lose the beat and start failing worse.