Turn-based tactical games are all about tough choices, and XCOM: Enemy Within does an outstanding job of piling more of those into the first half of the campaign against the alien invasion that began in last year’s excellent XCOM: Enemy Unknown. But as awesome as it is that developer Firaxis has given us so many more toys in this expansion (on PC – it's available as a stand-alone game on Xbox 360 and PlayStation 3), the aliens could’ve used some more help to keep the last months of the war competitive.

Performance Enhancement

There are a ton of great changes here, but the biggest is the addition of a new resource to most of the tactical maps. Known as Meld, it’s used to buy powerful new genetic and cybernetic upgrades, and Enemy Within deviously dangles randomly placed cannisters in front of our noses. Their ticking self-destruct timers forced me out of my usual conservative patterns by pushing me to explore the map quickly, and prompted me to take exciting risks with the lives of my troops. As a direct result, my XCOM body count was much higher in Enemy Within than it has been on recent Enemy Unknown playthroughs (on Classic difficulty), and that’s reinvigorated the sense of danger. Loading

Meld leads to another big improvement: a broader early technology tree with several viable paths. Almost immediately you can choose to delay important weapon and armor research in favor of unlocking enhancements that let soldiers auto-heal, aim better after a miss, jump to rooftops, and more. Layering those abilities on top of the existing skill tree (which has also received some notable rebalancing) makes the number of useful combinations and possible new tactics huge, and the drive to gather more Meld strong.

Alternatively, you can spend Meld to convert a soldier into a mech trooper for access to a whole new skill tree, and some powerful heavy weaponry. They’re not as indestructible as they look, though – they can take a lot of damage, but they’re also huge targets and can’t take cover, so they end up as useful tools that reward good tactics and working with the rest of the team rather than blunt instruments. But speaking of blunt instruments, the Kinetic Strike is joyfully satisfying to use, as it blasts enemies clear through walls if you can get close enough.

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The Late-Game Beatdown

Between those upgrades and new stat-boosting medals, Enemy Within poses another difficult choice: do you spread out your upgrades to slightly enhance your whole lineup, or pile them onto a few elite soldiers and risk losing it all at once if a Sectopod gets off a lucky shot?The Foundry upgrades have become much more important as well, due largely to the new Tactical Rigging upgrade which allows every XCOM soldier to carry two pieces of equipment instead of just one. That’s a hugely powerful change, and it makes Experimental Warfare a viable choice for research right off the bat, further widening your options and replay value.

Here’s the thing: even playing on Classic difficulty, once you reach the mid-game and build up some momentum, XCOM starts beating up the alien menace and taking its lunch money. If you thought the squad of high-ranking soldiers you had in Enemy Unknown was badass, Enemy Within’s enhanced squad puts them to shame. With a few well-equipped majors and colonels, neither the aliens nor the new Exalt faction have anything capable of standing in their way.

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Getting going in the early months is tougher, though. The invaders get some nasty new flying stealth enemies called Seekers, who wait to prey on exactly the kind of behavior the hunt for Meld promotes: spreading your soldiers out thinly across the map. That builds some great tension before you develop detection technology, but they become pretty weak once you have Snipers with battle scanners or, better yet, a soldier with skin that tingles when enemies are near. We also meet the Mechtoids, cybernetically enhanced sectoids who gain a shield when buffed by a regular sectoid. They look cool, and bring the sectoids back for another round after they become obsolete, but Mechtoids are pretty straightforward fighters and not much different from tackling other heavy enemies.Where the fight gets interesting, at least for a few rounds, is in Covert Operations missions against new human enemy called Exalt. Fighting them feels dramatically different because of two new mission objectives: one that’s basically an escort mission but without the dead weight VIP, and another that’s a two-stage territory holdout mission against waves of troops. The Exalt soldiers that swarm you with huge numbers use equipment comparable to XCOM’s, and they can put up a good fight if you don’t kill them quickly. But by the time I narrowed down the location of their hidden base by completing several CO missions, they were no match for me.

The lopsided late-game balance is made worse by the two series of scripted missions that come with big rewards at the end. Both the Slingshot DLC missions from Enemy Unknown and a new set play out identically each time you play them, allowing you to easily ambush enemies after the first couple of times through. The new set loads you up with extremely juicy rewards that make the ending even easier, and defeat the purpose of psi testing. Fortunately, Firaxis allows us to disable those mission sets when starting new games.

Endless Invasion

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Over the past year I’ve grown to know Enemy Unknown’s maps like the back of my hand, so Enemy Within’s large injection of new maps and locations is a huge improvement. Finally, UFOs can be shot down in urban environments or a rural farm, not just in forests anymore. Just as importantly, it reuses lots of Enemy Unknown’s maps in new contexts, starting your squad in a different location or using them for terror missions. Combined with having to take different approaches to existing maps to chase Meld cannisters, there’s a lot more variety. Plus, a pair of new scripted story missions, which I won’t spoil here, are both surprising events that play out unlike any other mission in the campaign.

There are still quite a few minor bugs around, including occasional frustrating line-of-sight problems and goofy animation glitches where a sniper will use the model for his rifle when firing his pistol. But the good news is that I experienced zero instances of the dreaded teleporting aliens bug – that one appears to be vanquished at last – so I never lost a soldier due to a bug.

I’ve also successfully played several multiplayer matches without the desync bugs that crippled Enemy Unknown. So even though it has an absolutely terrible and confusing squad loadout screen, taking a squad against a human opponent is now a good tactical challenge. Losing a head-to-head match because of a bad roll kinda stings, though, so you can’t take that too seriously.