A cover system is video game gameplay mechanic that allows a virtual avatar to hide from and avoid dangers, usually in a three-dimensional world. This method is a digital adaptation of the real-life military tactic of taking cover behind obstacles, for purposes of attaining protection from enemy ranged or area effect attacks, such as gunfire or explosions. Similar gameplay elements can be traced back to as early as 1986, in Rolling Thunder. Later games which refined the system include Bonanza Bros., Blackthorne, Time Crisis, Metal Gear Solid, WinBack, Police 911, Splinter Cell, Kill Switch, Gears of War, Uncharted, Mass Effect and Vanquish.