Platform: PC, PS3, and XBox 360

Developer: Firaxis

Where to get it: Steam (for PC), Retail (for PS3 and XBox 360)

Price: $29.99 (PC), $39.99 (PS3 and XBox 360, includes base game and previous content)

GAME GRADE: A-

Good Triple-A strategy and tactical games are hard to find these days. Similarly, worthwhile downloadable content is also hard to find. Thankfully “XCOM: Enemy Within,” an expansion to last year’s “XCOM: Enemy Unknown,” provided a good example of all three, though its cost can be difficult to justify.

Last year, Firaxis released “XCOM: Enemy Unknown,” an incredibly well-made reimagining of the famously challenging “X-COM” series from the ‘90s. Like its turn-based-tactics predecessor, the new game puts the player in command of a secret multinational organization in the near future tasked with repelling an alien invasion. Just like the old game, “Enemy Unknown” is split into two parts: a strategic component where players research recovered alien devices, recruit and equip soldiers, dispatches fighters to shoot down UFOs and deploy soldiers to combat aliens on the ground; and a tactical component, where players control the troops they sent out in turn-based battles against aliens.

It was a good balance between the high level long-term planning of allocating limited resources for development projects and equipping your forces, and the constantly shifting controlled chaos of the tactical battles.

Both elements were fun in their own right (the tactics side was impressive enough to inspire others), but the real genius of the system was how they played into each other: You spent half your time in battles trying to ensure that you can recover as many resources and researchable items can be recovered, and then you spent the other half of your time back at base researching and building new toys for your troops to test out in their next battle.

“XCOM: Enemy Within,” as an expansion, struck an excellent balance by adding just enough to revitalize the formula without changing things up too much.

In terms of the tactical gameplay, “Enemy Within” didn’t shake up the established formula too much; it still involves moving your troops about a square grid, putting them into cover, and shooting your enemies. Flanking, elevation, cover and range all affect how your troops and enemies perform. This remains, but new enemies and new weapons are thrown into the mix, which added considerable variety (and difficulty) to the game’s early hours; something that was a bit lacking in the base game. This is due to the game’s “early” period being extended. As with the rest of the game, “Enemy Within” will take you longer to complete than a run through of “Enemy Unknown.” This is actually a good thing, since it keeps the enjoyable level of challenge and uncertainty that characterizes the early game persist later in the campaign.

“Enemy Within” added many new options for players to explore within a playthrough, with new equipment and powerful ways to modify your troops, new things to research, and even a new resource to manage. All of this leads to increased complexity on the strategic level and an emphasis on making efficient use of very limited resources. Do you chose to modify some of your troops genetically, Captain America style, or do you use those same resources to create powerful cyborg combat suits for a select few of your troops? But, if you do that, you might not have the resources to build armor and weapons for the troops that you can’t modify. Couple that with more things to research, and you have the basis for an interesting game where you need to make long-lasting choices and hope that you can make it work. It builds tension, which leads to a great feeling of accomplishment when you make it pay off.

On the strategic layer, where the big-picture fun happens, the new big change was the inclusion of an entirely new kind of enemy to fight: an alien-sympathizing faction of humans called EXALT that serves as a direct foil to your XCOM organization. In practice, EXALT added new missions to undertake on the tactical side and a scavenger hunt plot as you hunt down their cells around the world in an attempt to take out their headquarters and end the threat they pose for good. While they’re active, they made the job repelling the alien invasion harder by stealing your funding, interrupting your research, and raising panic in the nations that fund XCOM, making those nations more likely to back out of the program (taking their funding with them).

In tactical missions, EXALT tended to use your same tricks, as their soldiers have all the same abilities as your own. It’s a nice change of pace from fighting aliens, but it ends up feeling like you’re playing a multiplayer match. They’re interesting the first few times you fight them, and they do add a new strategic wrinkle to consider, but they begin to feel like a hassle after a while (which may very well be the point, encouraging you to want to end them for good, but it’s still annoying).

XCOM is a game for which story has never been a major component of (the well intentioned, but ultimately mediocre “The Bureau: XCOM Declassified” from this August showed why it’s best to keep it that way), and “Enemy Within” stuck to this philosophy. A couple of self-contained mini-plots (called “Slingshot” and “Progeny”) revolving around specific soldiers added some color, but the story of XCOM is always what you write yourself, thanks to the freeform structure of the game. Customizing soldiers and coming up with your own imaginary stories is as deep as narrative gets here.

I had some complaints about the gameplay in “Enemy Unknown”, and even though “Enemy Within” makes a valiant effort, it doesn’t manage to clear up everything. Shifting between zoom levels on the tactical side of things still is problematic, so commanding troops on maps with multi-story buildings is much more trouble than it should be. Additionally, there’s little indication of your troops’ line of sight in tactical battles, which sometimes causes issues with targeting enemies and positioning soldiers. Still, these problems don’t cause issues very often, so they don’t drag the quality down much.

Finally, I need to get the cost issue out of the way: “Enemy Within” costs differently between consoles and PC. On PC, you need to have the original “XCOM: Enemy Unknown” (released last year and costs $49.99 on Steam) purchased and installed on your computer, then you need to purchase “Enemy Within” for $29.99. Consoles, on the other hand, don’t need to download “Enemy Within,” instead, console players can purchase a complete package at retail stores for $39.99 that includes the base “Enemy Unknown,” the “Enemy Within” expansion, and the additional content packs that were released previously. The problem with the console purchase is that you essentially have to repurchase “Enemy Unknown” if you already own it.

All that said, though, “Enemy Within” is well worth the money, and it’s an outright steal if you don’t already own it for a console.

So, with all that taken into account, I’d give “XCOM: Enemy Within an “A-” It’s not a perfect expansion, but it is pretty darn close.