A really interesting concept. It's easy to understand, but difficult to master, the first levels were quite frustrating as I understood, but didn't yet feel how it worked, but later, counting the timings was really fun. I would suggest, though, adding some sort of ability to briefly view the level before the first run, like a light blink, so that players wouldn't need to completely guess the level (or was that your intention?).
The metronome sound really created an interesting atmosphere, though maybe having some background ambience to complement it could elevate the vibe more. If you were to expand the game, I would suggest maybe trying out adding some music to parts of the game, I can imagine the metronome could get quite tiring by itself in a longer playthrough.