When entering Proef Rotterdam at the opening day, guests were asked for their date of birth. According to this information we could track their astrological element; water, fire, earth or air and tied a coloured ribbon around their wrist to distinguish between each. We served everybody his or her own element-specific food. The opening lasted the whole day. In the first two hours I noticed that there were only air and earth people visiting. I started to get worried that we would run out of white and brown food and have lots of red and green leftovers. Finally the water and fire guests came and balanced things up. Later on I read that apparently water and fire people have a tendency to be late.