Interesting concept that you have to watch and spot suspicious behaviour. In the current state I found it a bit easy after the first two runs in singleplayer because most of the time the first person going to a terminal is the spy. If the spy and the authorised personnel would behave a little more alike it might spice things up. Maybe adding another one or two NPCs might help also or instead.

I didn't test multiplayer with another person, only by myself, but the fact that both players stand still unless they hit a key gives the other one away if you don't hold down a key right when the game starts. At least it seemed common that the NPCs started moving immediately. You could try to add some random delay to the NPCs before they start moving, or let the spy chose one before the game starts.

This could become a really intriguing game if you add some different things to do for the spy and the other NPCs and introduce some kind of routine they have to do, randomised at some extent, so it's more challenging for the spy to blend in and more challenging for the detective to spot a good spy!

Wow, an extra multiplayer mode in 3 hours? That's nice accomplishment. The game kept me on my heels all the time and I was mostly running around trying to prevent anyone from touching the terminal; it was fun xD I also like the aesthetics.