In this arcade shoot'em up your mission is to infiltrate the alien fortress during eight levels, and to destroy the fortress and the alien.
Sitting in Ajax H.Q., you must pilot the remote controlled drone ship to do this. The drone represents jet fighter (behind view) and helicopter gunship (top-down view). It may be moved on the screen, fire air-to-air and air-to-ground guns and pow bomb. Limitless hordes of mechanoid invaders, whose sole intent is the total domination of the Earth, will try to stop you. Exit from each level is guarded by the powerful boss, who you should eliminate.
There are two versions of the arcade version (Typhoon in Europe and Ajax in Japan) which only differ in the order of the eight stages. The DOS and Sharp versions are based on Ajax while the Commodore 64, CPC (five levels) and ZX Spectrum (six levels) versions are based on Typhoon. The PlayStation 4 version includes both arcade versions.