Right now until Sunday at 10AM (September 13, 2015), you can play XCOM: Enemy Unknown for free on Steam. During this time, you can purchase the game for 75% off if you like what you play during the weekend. There is also a special XCOM 2 pre-order bonus to reveal.
Also starting today, fans can pre-purchase XCOM 2 for $59.99. For those who pre-purchase XCOM 2, they will receive the Resistance Warrior Pack, which will offer additional soldier customization options such as bonus outfits and facial war paint, as well as a Survivor of the Old War, who will instantly show up as a new recruit in the Avenger’s barracks.