XCOM: Enemy Within

XCOM: Enemy Within is an expansion pack for XCOM: Enemy Unknown - not a sequel or a spin-off, despite arriving as a separate, full-price app.

So it's still the same taut strategy game about fighting turn-based battles against aliens before returning to base to research new weapons, launch satellites, build labourites, and sort out the world's ET problem.

And it has the same story, same missions, same mechanics, same alien enemies, and same cutscenes we described in our 2013 review. There's just more of it, and more to it.

Take Meld for example - a new resource that can be used to give your soldiers cybernetic implants like super pupils that improve your aim, chameleon-like skin that renders you invisible, and bionic legs that let you leap onto rooftops.

You can also use it to craft mechanised exosuits called MECs, which turn soldiers into walking tanks that can't take cover (but can provide it), and can fire flamethrowers and rail guns.

These new powers are introduced almost immediately and change battles radically. Plus, the way you uncover this stuff completely alters the way XCOM is typically played.

As these precious few Meld canisters self destruct after a few turns, you must rush into battle to collect them in time. This forces you to mix up the old play style of slowly creeping from cover to cover, hammering on overwatch and clearing out buildings room by room.

You need to dash, use the assault class's run and gun ability, and throw caution to the wind. It's risky, but more fun and a nice change of pace compared to vanilla XCOM.

Enemy Within also adds new enemies. There's an invisible squid-like nightmare called the Seeker which slowly strangles a soldier to death unless someone else shoots it off, and human combatants who bring significantly different mission types to the campaign.

Aside from that, there are lots of little changes, including more maps for random battles and the asynchronous multiplayer, a second item slot for each soldier, and medals that give even more stat boosts to your favourite soldiers before they're cruelly snatched away by the jaws of permadeath.

This iOS port is pretty similar to the last one, with the same low-resolution textures and flat lighting, despite interim advances in Android tech and iOS 8's Metal framework.

Then again, that only affects the rare up-close scenes and the game still looks quite stunning in the standard isometric view (flickering shadows not withstanding).

The controls seem better so it's easier to spin or zoom the camera on command, and while entering buildings or scampering up to a higher elevation is still a little fiddly it's less of a hassle.

This expansion annoyingly adds a new problem where sounds sometime come out super loud from one ear of your stereo headphones in an annoying, unnatural fashion - hopefully just a bug that's fixed in a patch.

Enemy Within certainly makes XCOM feel fresh and exciting again, and the new additions will appeal to diehard fans of the original who want something different for their next ironman run

But as it's delivered as a separate app, rather than an in-app purchase for the original game, it's tricky to recommend to fans of the original game unless you absolutely adored it and crave more innovation, variety, and depth to the career. In which case, fill your boots.

But if you've never played an XCOM game before? This is an ideal entry point - it might be a little less accessible (and you can't turn off the complex new features like in FTL) but it's undoubtedly the superior version of an already excellent game.