Question: does your whole body have to be offside

Answer: No, Offside is one of the laws of association football, codified in Law 11 of the Laws of the Game. The law states that a player is in an offside position if any of their body parts except the hands and arms is in the opponents' half of the pitch and closer to the opponents' goal line than both the ball and the second-last opponent (the last opponent is usually but not necessarily the goalkeeper).