I'd tried that too (often has to be done for games on itch, I think it's a Unity bug), but it then says "Final Shot 1.2.1.app" was purchased using the App Store on another computer. To use "Final Shot 1.2.1.app" on this computer, sign in using the Apple ID and password used to purchase it."
Great use of the assets, it looks really good and it would be neat to see this expanded on. The controls are really stiff though, it would've been nice to have a sensitivity slider or something similar.