Change the Game: Uno

If at any given time a player has one card in his or her hand they must call out "Uno" before the turn is ended or before the card is played. If they do not, exile the card.
Whenever a player plays a land card or spell only spells that share a color with that card may be cast. If a player casts a spell that does not share a color with the most recent land played, all other players may draw two cards, then discard a card.