The XCOM: Enemy Unknown free-to-play weekend on Steam has begun, and ends on Sunday September 13 at 10am PT / 1pm ET. The award-winning strategy game and the Enemy Within expansion are both heavily discounted at 75% off, bringing the price down to $7.49 each. Purchasers will keep all the progress made during the free period. Those who want the complete XCOM experience might also want to look into picking up The Bureau: XCOM Declassified, since it's on sale for $4. 

XCOM 2 is also available for pre-order starting today. The sequel is expected to release on February 5, 2016, and pre-order customers will get the Resistance Warrior Pack - which includes outfits, headgear, custom facial warpaint, and instantly unlocks a character to recruit - for free.