Daioh (Great King) is an arcade game developed by Athena Co. Ltd., and released in the US by Sammy in 1993. It is a conventional vertical-scrolling shooter, but with uniquely immense enemies and bosses.
In the near future, Earth is invaded by warrior aliens who worship crustacean deities and are looking for sacrifices and new believers when they discover Earth. With the alien's advanced technology in mech construction, they cripple Earth's military with Earth's oldest religious structures being their first target; in their places the aliens build their extraterrestrial temples and enslave mankind to serve in the alien's religious bidding. A strike team is eventually assembled to rid Earth of the aliens before they start running out of human sacrifices.
The gameplay to Daioh was typical of most shoot 'em ups in that the player had a trio of different weapons such as a vulcan cannon that, once powered up, spread out across the screen, a missile barrage that would eventually launch homing missiles and an electrical-dsicharge weapon that would shock enemies until destroyed and could spread on to weaker enemies. Players were also able to accumulate bombs of various types. While the Japanese version used a typical power-up system where roaming colored icons change the player's weapon, similar to Toaplan or Seibu Kaihatsu games, the North American version had a very different gameplay system with a 6-button layout, where players had access to each weapon with a different button press, similar to Radiant Silvergun.
Missiles - An array of homing missiles and straight firing rockets that increase in number with upgrades.
Lightning - Homing electricity weapon that seeks everything within the space-jet's range.
Fire ring - A ring of fire that spirals out from the space jet and covers a fair radius of damage.
Large bomb - A large powerful bomb that detonates in front of the space jet and does a serious amount of damage, but has a small blast range.
Laser bomb - Three large blue laser beams that covers the vertical length of the ship, but only does acceptable damage.