Trap the J-atoms into smaller spaces in order to make at least 75 percent of the chamber disappear. You can check on your progress by looking at the area cleared at the bottom of the screen. The wallbuilder can sustain only a limited number of atomic hits. Each time it is hit, it loses one chamber life. The number of lives left is displayed in the upper-left corner of the screen. If two atoms are free in a chamber, a wall progress can be hit once. A second hit by a J-atom ends the game. You are allowed an additional hit for each atom in the chamber. The game ends when the wallbuilder is destroyed by atoms or when you run out of time.