flamebirde's rule: when playing a card of the same suit. must be either 1 higher or lower than the previously played card.
rob_gandy's rule: when three cards of the same value are played consecutively, order reverses.
brainy's rule. diamonds skip next player's turn.
miss kitten's rule: spades can only be changed to hearts.
framm's rule: a face card played on top of another face card skips that player's next turn.