there needs to be some sort of effect when you put 2 or 3 of the same gems into a tower. Example are such as the damage, chance, rate, of that gem goes up
Tip for Spitfire (Flamethrower) : When you are about to run out of ammo, or reloading, you can press Q then E and then your flamethrower has no reload :D. Example: Spitfire has no ammo, switch to pistol, switch back, Spitfire is fully reloaded :D