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.

Meld leads to another big improvement: a broader early technology tree with several viable paths. 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.

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. 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. There are a ton of great changes here, but the biggest is the addition of a new resource to most of the tactical maps. 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. 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.

Xcom enemy unknown vs enemy within