Love the art and music with this concept. All works together well. The actual rythm part of the UI with the buttons was well designed. Rough part is its easy to miss the rest of what's happening as I laser focus in on it. That is of course not the fault of the game and isn't meant in a negative way. Just took a minute afterward to take in more of what was happening and realized I missed a decent amount of cool environment and some UI on the side informing me of the current ugrades/downgrades.
From a feedback standpoint I have to agree with the issue of flow. The base concept of an upgrade and a downgrade is super cool. It generally works well so if you can figure out a way to present it that doesn't interrupt flow you have a great formula going.