Blackjack

{4}{u}: All players reveal cards from the tops of their libraries until they reach a total mana cost of at least 17. After that, they have the option of stopping or continuing to reveal cards. If a player reaches 21, they win the game. If they go over 21, they lose the game. Otherwise, the player with the highest total draws four cards. Then put all cards revealed this way at the bottom of each library, then shuffle.