In spite of the game saying that time only moves when you move, time only actually slows down when you are still. This doesn't make sense until you realize that the main character probably has to breathe.
Confirmed by one of the secret terminals.
The red-text entity that contacts the protagonist in the beginning repeatedly tells them to stop playing, despite actively brainwashing them to keep playing, through the SUPER HOT hypnotic message. This is to force the protagonist to ''choose'' to keep going, seemingly of their own will, and thus reinforcing the brainwashing.
The fourth level has police cars, which implies the enemies you're killing are police officers. Another simply says "BREAK IN" as you crash into what seems to be an antique shop through the skylight and kill everyone inside. With the revelation that those levels really happened, who else have you been killing throughout the game?
In Superhot VR, you hijack a plane.
The very first enemy you kill in the first level. Usually he dies before you even take control of the character, but if you're doing the unarmed challenge he just... stands there. He's unarmed and doesn't react, and if you attack him he moves around but unlike every other enemy in the game, never attacks you. Innocent bystander?
Player: Why do my enemies shatter when I kill them?
Red: WHY DO YOU ASSUME THEY ARE ENEMIES?
The main benefit from completing the Story mode is to unlock Endless mode. And the last mission? To kill yourself.
[You are now free...to play SUPERHOT forever.]
The elevator level. It's possible that 2 people with shotguns were waiting for the elevator to arrive so they could kill everyone in it but one of the 4 people on the elevator went crazy and started killing everything that moved. No survivors on either side.
