Polygon: "During a hands-on demo with the game at PAX Prime 2013, we played through a level of Enemy Within where we had to collect meld and fight the alien invaders at the same time. Meld, which is a new resource that has been added to both new and old maps, is used to create mecs and to give soldiers genetic mutation (g-mod) abilities. The introduction of meld means that players don't need to dig into their other resources in order to create mecs and g-mods, allowing them to allocate resources like alloys to other projects."
