The card deck consists of cards numbered 0-19, and to start a round of play each player takes three cards from the deck and places one in their "campfire" (a card holder) and the other two in their hand. They then do this twice more to have a hand of six cards and a campfire of three cards. Each player starts with a number of brain tokens.

On a turn, you must play to the central pile, playing a number higher than the current highest number. You can play multiple copies of the same number, and if you do, you place all copies of that number after the first one into the campfire of one or more opponents. You can always play a 0, which restarts the pile. If you play an 8, the next player must play lower than an 8, then the pile ascends again. If you play an 11, you take another turn. If you play certain high or low cards, you must roll the special die, which may have you play again, steal a brain from another player, swap campfires with an opponent, or take some other action.

If you cannot play, you lose a brain token, clear the pile, draw two cards, place one of those cards in your campfire, then start the pile again by playing from your hand. If you have fewer than three cards in hand at the end of a turn, refill your hand to three from the cards in your campfire. If you have played all of your cards, success! You have fended off the zombie animals, and all opponents lose a brain token for each card in their hand and campfire. If any player has no brains remaining, the player with the most brain tokens wins; otherwise, shuffle the cards and play another round, starting with the player who has the fewest brains.