The game starts with players holding 16 cards. These cards will have 0-4 microbes drawn on them (Sun, Moon, Mountain, Cloud). At the start of the game, the players may look at any and all of the cards in their hands. The game starts when the starting player places a card face up in the middle. The first player to find a card in their hand that either has one more microbe or one less microbe than the card in the middle and shouts out the name of the microbe that appears or disappears may play their card next. When a player places a new card in the middle, the other players must search for a card that matches the above criteria for the newest top card.

If a player places the wrong card in the middle or says the wrong microbe name,then shout """"ZOGEN!"""" to call them out. The player that made a mistake will be penalized. But making a mistake is no problem as long as no one shouts Zogen. If a player can't find the correct card to play, they may choose to intentionally play the wrong card .

Play continues until a player only has 3 cards remaining in their hand. This player is declared the winner. Ranking is decided by how many cards remain in a player's hand. The rules are very simple, but your head may begin to spin as new cards are quickly played on top of others. Players might also decide to give the microbes new names.