Planet Cannon

Planetary Defense. Invading fleets must fight and destroy the Cannon before they can capture the planet. You can upgrade the Planet Cannon in several ways and add a Planet Shield to make it harder to defeat.

Double Rate
Causes the planet standard cannon fires twice as often.
Shockwave
Adds a Shockwave Bomb launcher.
Nuclear
Adds a Nuclear Missile launcher.
Fleet
Creates an orbital fleet around the planet.
Auto-Destruct
Buildings and facilities are destroyed if the planet is taken over.