You must defend the starbase L-5 against a constant stream of blue Megalyte warrior ships and their deadly death ships. As the warriors reach the bottom, they launch an attack on your base, which can harm one of your four lives. The death ship takes aim at your base as it descends, firing as it goes, and will destroy your generator if it reaches your base, also losing a life.
As hordes of Megalyte ships descend, you can hold down the fire button to keep your anti-matter launcher in place. Moving the paddle left or right with the button released will shift the cursor and adjust your aim. If you're under attack or need to destroy a death ship, simply release the button.
Encounter at L-5 features 26 different game variations, with odd-numbered ones playable solo and even-numbered ones offering two-player action. Your score is determined by destroying death ships, which earns you ten points each. The further away the warrior ships are from you, the more points you'll receive.