Tough but I really enjoyed playing it.
I think the "random key for shooting" thing is .... a bit silly (especially cuz of how the UI is laid out making it hard to notice the keychange), something like having to hit a button sequence to shoot would restrict the randomization a bit, while keeping the gameplay mechanic (example: maybe left click is shoot but you have to maintain your weapon by hitting some random arrow sequence between shots, QTE style)
Feels like those fun little flash games you would send and try to high score between your friends. Love the core gameplay loop.