Doing everything server-side is not enough to prevent cheating. There are plenty of client-side tricks that can give the player an advantage, starting from simple visual cheats.<p>E.g. turn the opponent&#x27;s textures bright purple so you can see them better. Make the walls transparent. Aimbots that spoof mouse input.<p>The server must be authoritative or all bets are off, but you still do need client side anti-cheat countermeasures (stuff like verifying screenshots).<p>This stuff can&#x27;t be made 100% fool proof, so competitive games where big bucks are at stake must still take place with the organizers providing the hardware and the players located in the same room.