A small anecdote, I learned/realised this when visiting CERN (many years ago) and seeing someone in the control room playing a computer game on a laptop next to his big displays. So I asked and they said something along the lines that yes, it's allowed because otherwise the people would fall asleep, especially during the night shifts when their job is just to sit there and let the experiment run an be ready to react if necessary.

This seems like a useful solution, but I guess it's hard to do as a policy as there is a fuzzy line between the game taking too much attention and not being interesting enough.