The constant appearance of those golden disks really bring to mind the red crystals you see in the Raiden series. However, these have a more 'lost ancient advanced civilisation' aesthetic to them. Which is kind of reflected in the latter bosses' designs. And some of the background areas you fight in. Quite interesting.
Finally! Shadowserg does Takumi shmups bosses! For your information, the mysterious pilot is actually named Stranger, and it's an unlockable ship in the Dreamcast version.
Fact : Akio Otsuka voiced both Stranger and Stuck, with both of them being former closed acquaintances to the point Stranger was responsible that Stuck's wife was turn into a golden stone, hence Stuck willing to destroy the Medallion.
I personally hate games like this that punish the player for even the slightest imperfection and only reward players that have perfectly memorized every part of every level. These games, to me, seem too punitive to be fun. I like hard games, but this is OCD fifteen Ritalin levels of difficulty. I don't even enjoy watching this incredibly skilled player beat this game because I understand entirely too well how much work and effort went into the game just to get to this point.