Fortified Zone was ahead of its time in allowing the player to switch between characters during game play. Each character has their own strengths and weaknesses: Masato (the male mercenary) uses all the special weapons, but cannot jump. Mizuki (the female mercenary) can jump, but cannot use the special weapons. A top-down shoot-'em-up, the game had four multi-room levels, titled 'Field', 'Jungle', 'Caves' and 'Complex'. At the end of each level the player faces a 'boss' character: a cannon installation, a supertank, a dragon, a bulldozer and a large assault vehicle as the final boss. Items that can be picked up in gameplay include medical packs, flamethrowers, hand grenades, rocket launchers, 3-way machine guns and chain guns.
