Activate a System and take the action associated with it (moving the Space Sheep and Shepherds),
Play a card to move a Shepherd clockwise, or Play any card face down to the Defense Mat.
Additionally, a player may play a card matching the System occupied by the Wolf to attack (and knock the Wolf token on its side).
One player acts as the Supreme Flock Commander, managing the one-minute sand timer. If the sand runs out, Wolf attacks and players must discard cards from the Defense Mat, the deck, or their hands; if they can't, they lose the game. If the Wolf token has been knocked on its side, the Supreme Flock Commander may flip the sand timer before it runs out to avoid the Wolf attack, standing up the Wolf token and moving it to another System in the process.
Players who are Infiltrators will, of course, be attempting to delay action, make poor moves, and subtly manipulate the other players into making poor choices of their own. At any time players may point at one another in an accusatory fashion. If more than half the players simultaneously point at one player, this player is out of the game. He then reveals his Allegiance and:
If players have found an Infiltrator, shuffle the player's cards in hand and place them on the bottom of the deck.
If players have found a Defender, place the player's cards in hand on the face-down discard pile. On the ousted player's turn, Wolf attacks.
If the Defenders get all shepherds and space sheep to their matching systems, then they win the game. If the sand timer runs out and players can't discard enough cards – or if the number of Infiltrators matches the number of Defenders in the game – then the Infiltrators win. Players can customize Space Sheep! by varying the number of Systems in play (more Systems = more complexity), the number of tactic cards in the deck (fewer cards = greater difficulty), the strength of Wolf, the ratio of Infiltrators to Defenders, and the types of direction cards (more directions = greater variability)