Halley Wars is a Taito-published shoot-'em-up - though the development work was done by intermediary studio ITL Co. - that focuses on rebuffing an alien invasion that approaches Earth by hiding within Halley's Comet. Halley's Comet was last observable to the naked eye in 1986, when this game was originally released for the Arcade.
Though the game is an otherwise fairly generic vertical shoot-'em-up, it had one interesting challenge in that the player had to prevent too many enemies from leaving the bottom of the screen. Each enemy that got past the player's ship would then head on to Earth and cause untold damage, so minimizing this number was a necessary condition for victory. If the player lets the "Earth Damage" meter at the bottom of the screen hit 100%, the game is over.