I'm not good with words in English, so I apologize in advance if I sound rude or offensive. I just want to offer some helpful advice.
What you have here is a good beginning, but to be honest, it currently needs a lot of work. I'll tell you what I personally think could make it more enjoyable:
- About the graphics, if you're going for pixel art, you should try to make the different objects with a similar pixel size. The character sprite's amount of detail contrasts too much with the rest of the background. Same goes for the musical notes.
- Also, the button marks aren't circular/square/like anything. Their shape looks so off putting.
- The letters, though. The 'Q' in a non-pixelated font?
- The music is a good selection, but the songs are too long, in my opinion. I got tired and I wasn't even through a third part...
- You should consider making the notes synchronize with the song's tempo. It just felt like mindless button pressing.
- To which I may add, you can literally button mash through every note without any penalty.
- The UI buttons just don't work. You say two clicks may be needed but, after a song, the UI may even stop working at all! (the buttons react to the clicks and are pressed, but don't do nothing at all).
- This is personal, but I believe the clouds move so fast they distract my attention from the musical notes. But that may be just me.
I hope you find something of what I said of any use. :) This feels like it could be a great relzaxing game! Cheers!