O.S. is the Bright, enthusiastic A.I. that is responsible in charge of the game's UI. she speaks in very bright, happy enthusiastic tones. Think of a hyperactive version of Cortana from the Halo series, however the performance should be a bit more emotional and over the top, like some kind of infomercial announcer. (on a side note I swear to god that if anyone does a Billy Mays voice I will be livid).