In Silly Cow, players start with a hand of nine cards, each showing one of four different farm animals. In turn, they either play one of the cards to the discard pile, triggering an effect that depends on the kind of animal: draw a card, everyone passes a card, etc., or they play two of the same cards. In that case, the normal effect doesn’t apply, but the next player gets a negative card and places it openly in front of them. This card is passed on whenever someone plays a pair of that animal.

When a player gets rid of their last card, the round ends and the two players with most remaining hand cards receive penalty points, to which they add the penalty points on the negative cards in front of them.

The player with the fewest points after three rounds wins.