Last night's Arcade Archiver stream saw former Athena programmer (and current Cosmo Machia CTO) Tsutomu Tabata reminiscing on the making of Daioh, the 1993 Athena-made vertical STG that was just reissued for the first time via Arcade Archives—it's a solid imitation of the popular arcade STG of its day, and Tabata was very upfront about how it started development as a straight Tatsujin clone until they played Raiden, at which point it was retuned to split the difference between those two particular games.
(The international version, included with this reissue, has a unique wrinkle: instead of a traditional two-button, shot/bomb system with pickups, it uses a six-button control scheme that lets you access every shot & bomb type at will via individual buttons.)
It's also known for being quite tough: on top of having a relatively high bullet speed from the jump and a relatively large player hitbox, it also features an aggressive rank system that shoots up very quickly and is hard to mitigate, so you kinda just have to muscle through some bullshit if you want the full clear. For reference, the big Japanese STG community difficulty ranking index puts the Daioh 1-ALL alongside 1-ALLs for games like Same!Same!Same! and Gunbird 2, and the full 2-ALL alongside full clears for games like Ketsui, Mushihimesama Futari Black Label God, Image Fight and one of the games they were imitating, Tatsujin Ou.
The rank system was broadly understood to hinge on the typical factors (DIP settings, lives/bomb stocks, collecting items, basic rank-over-time, etc) but, as Tabata explained, it's actually a little more involved than anyone would naturally presume—dubbed the "Oyaji System", Tabata endeavoured to engineer a rank system with the specific purpose of identifying the typical tactics employed by the average flailing salaryman or other casual/novice players... and it ultimately ensnared everyone else, too, but not anymore! (Most of these systems apparently also made it to Daioh's unofficial successor, 1997's Shienryu.)
heads up: at the request of the original programmer, Hamster patched Arcade Archives Daioh with an optional display for the rank value, like so
