Stargate

In Stargate (aka Defender II), you flies a spaceship above a long landscape, saving humanoids from alien invaders who are out to abduct and mutate them. The gamefield wraps around, so flying constantly in one direction will eventually bring the player back to their starting point.
The spaceship main weapon is a laser cannon that can be fired rapidly in a long horizontal line, but also has a limited supply of smart bombs (which can destroy every enemy on the screen) and “Inviso” cloaking energy (which makes the ship invisible, being able to destroy any enemies it comes in contact with), both activated by the second controller.
A central feature of the gamefield is the Stargate itself, a series of concentric rectangles. The operation of the Stargate depends on the current game conditions.
If a lander is in the process of abducting a humanoid, flying into the Stargate will teleport the ship to where the humanoid is under attack.