The object of the game is to be the player with the lowest score. Points are scored by adding the point value of your cards when each hand ends. The game ends when one player's score totals 100 points or more.
Each player is dealt four face-down cards. On their turn they will either draw a card from the deck or take the top-most discarded card. They will either switch it with one of their four cards, trying to make it lower (if drawn), or discard it. If the discard is selected, they must switch it with one of the four cards. All four cards are always face-down, forcing the player to remember them.
This continues until the deck runs out or someone has collected the one B-Low card and calls for the end of the round. Points are totaled by cards saved, lower is better.