EuroGamer - Five years ago it was cover systems. Thanks to Gears of War, it got to the point where you couldn't go to the bathroom without being invited to crouch behind something by a whopping red icon. Then for a while it was experience systems in multiplayer. They had been done before, of course, but we can blame Call of Duty 4 for catapulting them to front of mind. Nowadays even 2D platform games on your mobile phone have XP systems.