St. Peter Erosion (web)
On this website, the user is presented with a screen asking them to click to continue. When they click, the computer records the coordinates of that click and then displays a pixellated drawing of a foot with a spot worn away where they clicked. Again this is recorded so that the next viewer sees their clicked spot worn away plus the wear caused by all the previous viewers.
Visitors to the Vatican regularly touch the foot of this statue and, as a result, the foot has become worn down over time.
