Star Castle

Star Castle is an arcade game released in 1980. It was also ported to the Vectrex.

Gameplay
You control a small spaceship that, like the one in Asteroids, can rotate, thrust, and fire. You have been assigned to take out a gun turret that is hiding behind three layers of shields, but the job is not easy. First of all, each section of shield requires two hits to be destroyed, and if you destroy all its sections, the gun turret simply generates a new layer of shield from the inner layer out. Secondly, the gun turret sends out tiny heat-seeking missiles that go after your ship. You can easily destroy them, but they will earn you no points. Thirdly, when you open enough gaps in the shield layers, the gun turret can launch a fireball at you if you're in its line of sight. Destroy the gun turret within and you'll earn a bonus ship as you are taken to destroy another gun turret hiding behind layers of shields. The game gets difficult as the heat-seekers get faster and the gun turret takes less time to be within line-of-sight of you to destroy you.