Strange Occurrences at Midnight

I was in the library last night for a long time reading my psychology book. A LONG time. By the time I left, the actual library part had closed and only the 24 hour cafe area was still open and it was well into the morning hours. I blame my RA Laurie for planning a floor activity that lasted until close to 10. (Just kidding Laurie!)
As I exited the library, tired and weary from my psych studies, I came across something strange in the middle of the campus.

It appeared to be some sort of game that they were all playing. Standing in a circle, they would take turns making a singular move and then freezing. The look of it was quite strange. I didn't understand it!

The resulting look of all the movements and such was comical to say the least, but I still don't understand. If they are out there again tonight, I might be joining them if for no other reason except to figure out this strange occurrence at midnight.