So sorry to hear that shooting has been an issue for multiple players. It works normally on my laptop (even on the web build), so I'm not sure where to begin troubleshooting this. I'll have to learn more about controls, I think.
Here's another thought. Since the dominant strategy is to keep the button pressed constantly, and there really is no reason to let go the button (e.g., there's unlimited ammo)...
...perhaps the ideal solution is just to have the character fire continuously, with no need to press the button at all. I think maybe I'll try that and see how it plays.
Thanks everyone for trying the game out!