The story is set in the future, as aliens have invaded in an attempt to harvest all of Earth's carbon resources (C-12 is a reference to 12C, the most abundant isotope of carbon). The player uses Lieutenant Riley Vaughan, a cybernetic human soldier, and member of the underground resistance. The player undertakes missions played out in a third-person view, killing aliens and cyborgs, collecting weapons and keys, and the like. Source: Wikipedia, "https://en.wikipedia.org/wiki/C-12:_Final_Resistance," available under the CC-BY-SA License.