Threshold

About Threshold

The player moves a spaceship, the Threshold, left and right along the bottom of the screen and uses its laser weapon to destroy waves of aliens attacking from above. When a wave is eliminated, another appears. As in Astro Blaster, firing the laser increases its temperature, and it cools when not in use. If the temperature bar fills completely, then the weapon is disabled until it fully cools. Once per ship, pulling back on the joystick activates a "warp drive" that briefly slows the action.

In the Atari 2600 conversion, the ship can be freely moved in eight directions in the lower portion of the screen, but lacks the warp drive ability.