Thanks for the review!
You're right! That is actually how the system works. But, after it's pressed, mouse input should be blocked. I suspect that when pressing the button, it becomes focused, at which point, ui_enter inputs (which is space and enter) would trigger presses again despite mouse input being blocked. Anyway, the bug should be fixed easily.
As for the boss going beyond the platform, that's actually something we're aware of and decided to put at the bottom of the polish list as it didn't seem to disrupt gameplay too much, though we will find a way to deal with that too if we decide to develop the game further.
Thanks for reporting the bug! I'm impressed you pressed space 126 times just to show that lol