Pretty fun game. I got stuck for a lil when I didnt unlock silver yet and couldn't get to the boss anymore but thats probably because I just randomly upgraded. That however was partially due to short press = upgrade and long press = read description. So I often ended up upgrading when I wanted to read the description.
I also encountered a bug on mobile. Later in the game sometimes when I started the next round(?) It would start just where I left off in the old round, so I pretty much instantly died. Usually that happened a few times and then I'd get an actual new round with full life and shield.
I also couldn't make the game a lil smaller on mobile so not quite sure what button I was actually pressing to start the game
Other than that, quite enjoyable game