Zombie Defense Squad is a first-person shooter in which the player has to defend a small town from zombie waves. To win a round, a certain amount of zombies have to eradicated from the map. Each killed zombie is rewarded with experience points (which leads to level-ups and automatically assigned bonuses like faster reloads or higher walking speed) and money. The latter is used between rounds to buy better weapons and ammo in the store. Each round adds zombies to the wave.
Kikou Heidan J-Phoenix + is an Action game released in Japan in 2002. The game adds some PF and an EX mode. In EX mode, each of the three PF can be customized, and each can be alternated in the middle to fight.
Attack of the Zolgear is an arcade game for one to six players released by Namco. It is a sequel to Galaxian3. This game used two LaserDisc players simultaneously for the outer space background, while computer generated graphics were overlaid on top. The environmental "theater" used for Galaxian 3 received this upgraded sequel in 1994.