The Officer class is your stereotypical buff machine, who gives out bonus to nearby teammates.
However, as a note, you will always need someone to play as the Tech class, as he provides the only tools necessary to progress through levels. There are several classes for you to play as, each with its own characteristics. Also, for those who prefer to get down and dirty, there are a few console commands that can be entered to turn the view into a first person fillet-fest. The game itself is played using slightly slanted top-down view, which is great for this style of game, mainly due to you being able to see the carnage in its surreal beauty. Good thing the story itself isn’t all that important.
The humans being mauled by alien creatures that happen to be coloured green thing, has been done a million times.
Humans struggling to survive using conventional means against, you guessed it, aliens. The story itself is your typical space survival deal. This gem does everything (for the most part) right.