[SYMBOL] [A] [B] [C] [D] [E] [F] [G] [H] [I] [J] [K] [L] [M] [N] [O] [P] [Q] [R] [S] [T] [U] [V] [W] [X] [Y] [Z] X-Com\: Enemy Unknown destroying balance 2nd X-Com\: UFO Defense emergence XCOM series interaction model for strategy games XCOM\: Enemy Unknown exploration in strategy games tech-trees in strategy games |