Bag of Butts is a "push everybody's luck game".
When it is your turn, you announce how many butts you want to draw for which butt group before your first draw. Then you draw exactly three butt groups from the butt bag. Once you have drawn all the butts from the butt bag, you choose which one butt group you want to score. Not only you yourself though but everybody will get butt points for each of their butts in the butt group that you are scoring. The next player will then add a random special butt to the butt bag before they, too, draw all the butts. These change the game up a little but, more importantly, each player butt is also worth an additional butt point for each special butt that is in play.
Once you reach at least 28 butt points, the game ends with the next reset. A reset happens either because a player decides against adding another special butt to the bag or because there happens to be one or more special butts in each of the three butt groups that a player draws. Just because you are the first player who reaches 28 butt points does not necessarily mean that you will actually win the game.
—description from the publisher