[douglas]

There is a storyline, but I don't think you can affect it significantly except by failing certain crucial missions and dooming the galaxy. I think there is some potential in the game mechanics for the player to make decisions that actually affect the story, but I don't think the stock game actually has any branches set up beyond whether you get praised or scolded after succeeding or failing a non-crucial mission. Some mods might have branching storylines, but I haven't played anything but stock.