Defending X for Y amount of time is a common objective type used in a number of different ways and is found in both single-player and multiplayer games. Such objectives appear in many action and strategy-based genres. In basic terms, the objective requires the player to defend something, whether it be an NPC, item, or location on a map for a specific amount of time. The objective is completed successfully if the player manages to maintain the defense for the full duration. Players must often face increasingly difficult opponents as time elapses before the objective is completed. In turn-based games, Y time may be represented by the number of turns required to defend an objective rather than a time limit set in real time.