IN MY TENURE as head of XCOM—a top-secret multinational organization dedicated to protecting Earth from extraterrestrial invasion—I've discovered futuristic technologies, rescued world leaders, developed a top-notch research laboratory, and shot more aliens than Bill Paxton and Michael Biehn combined.

I mention all this not just because it's an easy way to cover a huge swath of features at once, but also to impress upon you the scope of XCOM. As the game is effectively a classic turn-based strategy game, the intense level of detail and design nuance it's capable of is amazing. To wit: Every time you're asked to send your soldiers out on a mission, the game randomly selects a map from its massive list of pre-generated war zones. That may seem like a small feature, but this wealth of diversity when combined with random enemy placement and numerous mission types and objectives means XCOM has an immense amount of variety in its gameplay. Theoretically you could play this game 100 times without ever seeing a duplicated mission.

Those of you familiar with XCOM developer Firaxis know that it excels at creating games that utterly suck players in. "I'll just take one more turn," you think, before glancing up at the clock and realizing that it's suddenly 4 am and you've been playing for 12 hours straight. 2010's Civilization V is the most recent example of this, but somehow Firaxis has managed to make that addictive impulse even more intense in XCOM: Unless you hate the game's premise, you'll replay it over and over and over again.

I'd explain how cool the alien designs are, how surprisingly important world politics becomes, or how intricately detailed the character customization can be, but honestly, I don't have the time. There are aliens to kill, and that's what I do now.