This game is SUCH A VIBE. The sounds, music, and visuals are sick. It feels great, sounds great, and looks great! The only thing I don't really get is how it relates to the theme, which could probably be fixed with a little opacity change or something. For me, the echoes seems more like health. Either way, it's a SICK game.
I would probably add some more mechanics. Right now, the game is really just tactical button mashing (for me at least) and I would love maybe a few levels/power-ups that add a little bit of advantage (or lack thereof) to shake things up a bit.
I love how the music speeds up in the background. Again, "Reverb" has such great aesthetics.
Great job!