for mobile just drag your finger around and it will fire while following your finger. For PC you can either use space or if you want to use your mouse/touchpad(laptop) just click and it will fire (WARNING!: pretty loud on full volume) Click the yellow box on the bottom right corner to reload (for mobile) it's kind of slow and glitchy though...
I will make this an objective type of game (you'll get a mission) so it's a WIP (Work In Progress) + a first-person cam (first-person only accessable from PC) first-person also has a "NO AMMO" screen that will flash if your ammo is empty/0 ammo. P.S. about ammo: using a glitch, you can get infinite ammo (figure it out yourself!) Shoot at 0 ammo and press the reload button, it will mistakenly give you thousands of ammo. But you keep hearing the no ammo alarm ;)