The concept is definitely very nice! I love gameplay mechanics focused on indirect attacks. There's definitely a lot of room for improvement too - the game starts slow but then a whole horde of monsters spawn, the tutorial has to be skipped each time, and the controls are weird too - I need to take my hand off the movement keys to access the pause or upgrade menu, and what kind of game lets me use the mouse to aim, but not click to shoot? And then finally, I somehow softlocked the game by trying to access the upgrade menu again immediately after getting an upgrade.
For a counterintuitive game mechanic like this, an interactive teaching sequence would me so much better - for example, start only with unbreakable square mirrors that reflect at more predictable angles, and maybe some static targets too. Then you can slowly add more mechanics. Maybe even some kind of super enemy that requires a double reflection? For a game like this, I need to teach not just my brain, but my muscle memory too.
I hope you develop this concept further, it's a really cool one! If you don't, I might steal it instead ;)