Kour.io developer, don't change anything in the game, it's perfect. Just add a way to run, make the character automatically reload the weapon when they run out of ammo, make it possible to do the famous "bunny hop" in FPS games that makes players move faster, and remove vests if possible, so that everyone has the same HP and player skill is the only factor that makes them win. Don't make the game pay-to-win. Make money as much as possible through ads, but don't make the ads excessive to avoid losing players.