Drag the king to it's landing square (two squares, either direction)
Umm... pass pawn.. u mean en passant (yeah I know, we have to use french whether we hate it or not ;).
yes, en passant is a 'manditory' part of the game.. anything else is a variant (such as fisher chess.. try it).
Is it mandatory to play with the pass-pawn rule? Also how do you perform a 'castle-king' move?,