BS-04 is the fourth boss from Raiden III.
Details
BS-04 is a giant cone-shaped spaceship which uses a series of rocket boosters on it's body. The boss has three phases fought in sequence. It has guns all over it's body, most of which can be destroyed. Whenever a series of guns on a portion of it's body is destroyed, that portion is detached. Since the boss will be constantly sweeping the screen with bullets, it is recommended to destroy the guns to lower it's firepower.
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Concept art