The goal of Lose Your Marbles is to do exactly that. The game screen is divided into thirds: on the left are your marbles, and on the right are your opponent's; the middle third is open space. Each side gets five vertically sliding columns of different-colored marbles. When you line up a row of three, four, or five like-colored marbles, they disappear from your grid. If you manage five, you knock those marbles over to your opponent's side. Of course, your opponent is working to do the same. If marbles accumulate faster than you can dispense with them, you'll run out of room to maneuver your columns. Eventually, you'll get boxed in and lose the round.