Shows how to get the blue key in Doom 64 level 20, Breakdown.
There are 2 shootable switches in the starting area, and each will function only once. The switch shown in this video makes the blue key accessible; the other causes 1 or 2 Cacodemons to appear (number varies depending on the chosen Skill level).
These switches, like all shootable switches in the game, can be activated with pistol, shotgun(s) or chaingun. In some modern ports of Doom 64, the Unmaker can also be used to trigger shootable switches; but that doesn't work in the original N64 version.
Timestamps:
0:00 - Head upstairs
0:06 - Use pistol, shotgun or chaingun
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