Shows the location of what appears to be a broken switch or button in Doom 64 level 7, Research Lab. In reality it's meant to be a camera lens for a wall screen, seen at about 18 seconds here.
This video starts at the blue key's location. See https://youtu.be/xz2ukvCoGuU for a video showing how to reach all keys and the exit.
This is a 'no monsters'-style demo, made to quickly show the stated objectives without additional minutes of combat.
Timestamps:
0:00 - Blue key acquired
0:10 - Field of view from corner
0:18 - Screen shows same view
0:21 - Switch removes barrier
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