This is a very gentle, fun crystallization game that speeds up as it goes.

G.19. Prui Prui

Everyone stands in a group, closes their eyes, and starts milling about, looking for the Prui, who doesn't talk. Explain all the rules about seeking and joining up with the Prui.

When players bump into someone, they should shake his/her hand and ask, “Prui?” once.
If the other person asks “Prui?” back, then he or she has not found the Prui. [If there is no answer, the person is to repeat the question, to make sure.]
Keeping their eyes closed, each person moves on and finds another person to ask.

When everybody is bumping about, shaking hands, with strains of “Prui? Prui? Prui?” floating around the crowd, the leader whispers to one of the players that s/he is the Prui and how to play to the end.

The Prui is a sighted person, s/he opens his/her eyes, but must remain mute.
When someone bumps into him or her, and shakes their hand, asking gently, "Prui?" there will be no response. If this happens, players should ask a second time, to make sure: “Prui?” If there is still no answer, Eureka, the player has found the Prui at last!

Now the finder can open his or her eyes – becoming part of the Prui, too, and holding the Prui’s hand. When someone bumps into the new partner, s/he can shake with whichever hand is free, but not respond to the question. That’s how the Prui grows!

Players can only shake the Prui’s hand at either end, so if a player bumps into two clasped hands, he or she will know that the Prui is somewhere in the middle. To join the Prui, he or she should feel their way to the end of the group.

Soon enough, everybody’s happily holding hands, except one or two lost souls groping their way along the line of bodies. When the last stray joins up and opens his/her eyes, the smiling Prui usually breaks the silence by letting out a spontaneous cheer.