If a group of game players asked me to open the portal I spun them some story about the reactor mass being unstable, and sent them out to an area in front of the theatre, where they had to hold hands and jump up and down (in front of all the tourists LOL) in order to damp down the column of mercury blah blah some nonsense I made up. It was hilarious. They were also running the risk of being caught by the scary robot, so I got one or more travellers to stand on the balcony, scanning for danger, and sending messages via walkie-talkie to their friends out on the forecourt. I don't know if that explains how the game worked, but it was terrific fun, I think for everyone.
If the robot caught them all he did was cross out one of their scores, so not too horrible, but psychologically they were genuinely terrified of being caught - people would run up to me literally screaming with the robot (guy in tinfoil) on their heels. It's visceral I think.
several_bees was really on top form, coping with myriad problems, and organising an army of helpers like me and about 100 game players. I will look out for further events of this kind and I hope some of my lj-friends will come along with me.