The dynamics of the human population are complicated. New players arrive at a steady pace, but at the same time many veterans keep coming back (fig. 3.15), resulting in a relatively stable experience distribution. The median is 87 games, meaning that half of the games are played by users with a previous experience of 87 or more matches (25% with 387 or more).
The uniquely adaptive quality of the Tron web site is one of the reasons for such enthusiasm. One of our visitors described it in an eloquent e-mail message:
``I can actually see that the best robots now are better than the best robots of yesterday. (Specifically, all of a sudden when I logged in at 7PM yesterday, I could swear that there were sentient beings behind some of the robots)''3.8 .