|This article is written from the Real Life point of view|
In Adventure Mode, the fourth stage is Planet Zebes: Brinstar, where Samus is fought. Once defeated, a siren will sound, cuing the Warning Siren music to start. This plays on the 4-2DASSYUT level as the player character attempts to ascend the shaft. The entire sequence is meant to pay homage to the Countdown sequences in Metroid and Super Metroid.
The theme can be heard here: .