They were able to control the environment of the terrain by moving some markers. Moving the sun to the center of the camera would result in making a desert while moving it away from the center made the terrain snowy.
All this changes affected a little character placed in the center. Extreme weathers would make him feel bad. But, when having nice weathers, he would wave his hat and say hi to the people.
Here are some photos from the event:
Thanks a lot for everyone who tried it out!