I think I understand the meaning of this ending. Yes Origins is a game, and it is played by Samantha and Eddie. I think this because the map seems to imaginative, not realistic at all. The robots and dr. maxis having his brain chopped out and turned into a robot? I definatly think this is a game that Samantha and eddie are playing, thats why we see all the symbolic stuff in samantha's room. BUT at the end we here the alarms and maxis calling samantha downstairs and they talk about wishing it were real and that her dad, maxis, has a plan. I think this is taking place during WW2, the begging of when zombies takes place,I think this because of the alarms. Then her dad could have had the plan that made there game a reality and maxis successfully created the zombies!Then as we know Samantha Actually ended up controling them! and eddie could have grown up with samantha and he is edward, maybe. so now we come to what we have know about zombies previously and its a fight between samantha and edward for control of the zombies. so yes this is the origins and after their "game" maxis made it a reality. This is just my Thought.