Took me a moment to understand but it's a cool concept. Just a few notes:
- Sometimes the green arrows stopped working and the level couldn't be completed. Restarting the level does not fix it. I had to refresh the web.
- It could be nice to have some sort of preview so that you don't have to first fail the level, then program the algorithm by trial and error. Maybe the option to change the pipes mid song?
Still good job!