This game presentation is pretty top notch. I like the concept, but there's little to no feedback on whether you hit or miss the key and I have some real difficulties doing any action at all at some points.
Rythm games usually have "miss, bad, good, great,etc" next to the tempo bar whenever you hit it so you can know how good/poorly you're doing. I think if you add at least a "Hit" and "Miss" with their respective sound it'll make the game much more playable ʕ´•ᴥ•`ʔ
It'd also help if the music had something more pronounced in sync with the bars, otherwise it's a little bit jarring.
I think you can easily fix these and it'd make a big difference for your game ʕ •ᴥ•ʔ