3D Strategy video games are categorized based on whether they offer the continuous gameplay of real-time strategy (RTS), or the discrete phases of turn-based strategy (TBS). Often the computer is expected to emulate a strategically thinking "side" similar to that of a human player (such as directing armies and constructing buildings), or emulate the "instinctive" actions of individual units that would be too tedious for a player to administer (such as for a peasant to run away when attacked, as opposed to standing still until otherwise ordered by the player); hence there is an emphasis on artificial intelligence.