This game is also available on PS2, PC and Mobile + Flash.
the dot is obtained by pressing shift and apostrophe, which comes up with a small dot. when you activate it, you become a memeber of the green team, a hidden bug that makes you disappear from the player list and you can attack both teams : but be warned. if they see you then they will hammer on you, for both teams will eventually suss it out, and you will have a hard time staying alive :)