Controls consist of a trackball and two buttons, Energy and Decoy. The player controls a ship that can move freely within a nuclear reactor, seen from the top down. Swarms of particles follow the player and bounce off each other, the player's ship, and the reactor core. Any object touching the outer "kill wall" of the reactor is destroyed. Pressing the Energy button during a collision with a particle will cause it to bounce away at a higher speed.
While touching the core is not harmful, it continually grows in size, restricting the available space for movement. Two sets of control rods protrude from the kill wall; if the player knocks particles into all the rods of one set, the core shrinks to its minimum size before starting to grow again. The player starts the game with a limited number of decoys, which can be deployed by pressing the Decoy button in order to lure particles toward the kill wall, control rods, or either of two small "bonus chambers" at opposite corners of the screen. An extra decoy is earned by knocking out both sets of rods.
The player earns points for destroying particles or luring/knocking them into the bonus chambers so that they bounce off the walls. A set number of particles must be destroyed in order to complete each level.
In later levels, the core is replaced by a slowly expanding vortex that can attract the player's ship and destroy it on contact. One or both of the bonus chambers may be briefly sealed off at times, and the kill wall becomes invisible as well.
One life is lost whenever the player's ship touches the kill wall or vortex. The game ends when all lives are lost, with bonus points awarded for each unused decoy.