After playing this game for a good 15-20 minutes, I must say that it's not the best. It's a good concept but the execution of that concept is dreadful.
1. IF you're going to make a game like this, you need to have the buttons you have to press be more clear, for example the up button actually being an up arrow instead of the letter U. Further more on that is the fact that you can't really see the letters unless you're leaned into the screen due to how they are all shaped, it's easy to get them confused when you're not looking at the colours themselves, D and R look exactly the same if you aren't completely leaned into your screen.
2. Sight reading this game is incredibly difficult to do. The notes move very fast and there's some form of an input delay as well so you only really get a second to react to what's coming, if the button sequence is cursed then you're screwed, especially if some buttons overlap.
3. The entire right side of the target is completely useless. After failing a cue, they should either disappear or the target should be moved further to the right.
4. The game would be a lot better if you could customize the button layout, say for example the arrow keys are uncomfortable to use in this way so you'd prefer using WASD or any other keys other than the arrow keys.
That's all. If some of these things were to be improved on, this game could be a good idea/concept but for now it's simply not fun to play.
The artwork is great though.