I think a bunch of people have already said this, but the character art is amazing! I enjoy rhythm games, but I'm not particularly good at them (with the most recent FNF level, I can't even get through the first song on easy ;-; ) That said, the difficult of your game was perfect for me! It took me a minute to figure out the correct timing, but once I got it was very fun to play!
The chiptune styled music is also really good!
I see 3 songs on the menu, are they all playable? I'm not sure if I'm doing something wrong, but I always get the Sheep Girl no matter which I highlight. (I tried Chrome and Firefox just in case, but had the same result. I mainly use Firefox when browsing, but as a fellow Construct user, I've run into a handful of Firefox-exclusive bugs in my own projects)
If I'm doing something wrong, let me know 'cause I'd love to come back and play the other songs! If not, I'll definitely want to check this out as you keep working on it! (There's Continue-it Jam coming up if you want to join, *wink wink*)
One bit of feedback I had based on what I played was that I'd like more "impact" when hitting successful timings! Currently you get some visual feedback, but I think some sort of audio cue would make it more satisfying to score hits! It's possible you had more planned, so if it's on your to-do list, don't mind me!
Anyway, really nice work! Looking forward to seeing more. :D