Galaga: Demons of Death (1988)
Action - Shooter

Publisher	Bandai
Developer	Namco

There are larger enemies in the back that are green, and turn blue when you first shoot them. They sometimes send out a wave that will suck you up. Let them. When you are given your next ship, shoot the one that has your previous ship, being careful not to actually shoot your ship. If you destroy them and not your old ship, it will come down and dock next to you - you'll now have double the firepower.