Ikari no Yousai is a top-down overhead shooter by Jaleco and features a heavy armed warrior whose given task is to infiltrate a science laboratory and to find out what happened there. The uninviting place is now filled with legions of hostile aliens and odd-looking devices are scattered around every corner of the sprawling station. The player first comes equipped with a single Vulcan gun and a triple direction laser, but more sophisticated weaponry and items are later available such as the flamethrower or the reflective laser. As the game progresses, maps of the visited areas reveal their secrets and special booths give the player some clues on what exactly happened in the station (through simple animated cutscenes). But Ikari no Yousai is more than a simple overhead shooter, the game features many puzzled and some areas can be only unlocked by using a specific weapon or item.