Oh, it's a mess. If you're really curious there are some in-depth faqs that go into it. The good people on system11 regrettably sometimes mistake obscurity and bizarre hidden counters for depth, even though the list is pretty reasonable otherwise.
so ok it's time to defend garegga because i think it's objectively one of the best games out there. let's not toss this one aside just yet!
but first let's make a couple blanket statements up front (to the haters) and just trust me
1)
the rank system is opaque and that's ok. nobody was ever supposed to understand it down to the precise numbers. rather, the numbers are just necessary to create trends. i think the idea was that, since the game was designed for the arcade, people could get together and figure these trends out via experimentation. i personally think this is way past cool. you might not. but i don't think the game is at fault for being this way and not another way.
2)
if you accidentally read 1) and don't know what it means then ignore it3) fuck shmups forumanyway
why should i care about battle garegga? the #1 cool thing about battle garegga is that, in contrast to shooting games who only aspire to be about shooting or whatever, garegga has a single core focus that drives every aspect of its design. it knows what it wants to be. it has a reason to exist.
above all else,
garegga is an exploration of player autonomy.
and this thesis resonates throughout the whole game. your powerup system is designed so that, with a bit of strategy, you can get to almost-max power by the end of the first stage. your bomb system is designed so that you can hoard them for defensive use or fire off quick blasts offensively. and your option system is designed to allow you to deftly send firepower to where you need it most.
everything is permissiblenevertheless, while everything is permissible,
everything has consequences. and this is where the "rank system" comes into play. for those who don't know, rank is what people call this game's dynamic difficulty system. and the best way to think about it is
for every resource that you take advantage of, your opposition will take advantage of another of their resources in turn.
see, the rank system is crucial for giving all of these elements meaning. for example, take a game like dodonpachi. when a powerup appears, it's sort of a loaded proposition. you have no reason
not to take the powerup. same with bombs. the ideal of using no bombs is set forth, and any deviation from this ideal is a result of human flaw.
but in garegga's world, when a powerup appears, you're forced to consider the consequences. do you take it right now, or wait to power up? the answer is largely situational, and almost never black-and-white. the consequences are presented, but it's up to the player to act in awareness of them. a mantra is suggested—
take only what you need, make the most of what you're given—but it's up to the player to put it into action.
this is the soul of battle garegga, and it's why i strongly feel that it is worth playing by every student of game design.
(also: everything above is only the mechanical interpretation of the thesis. the way this thesis of autonomy actually plays out in the stage/boss design is even more incred. seriously)
oh and i'd also recommend batrider (it's basically an orgy in honor of player autonomy) and this lesser-known doujin called hellsinker which is a noble attempt to use the shmup fetish for systems to make a statement about that world and our world too. i'm not exactly sure what that statement is supposed to be though