We made an attempt to a Soccer game using 2 robots in each team. They were supposed to pass the IR ball at least once before they could attempt to score. We built a ceiling and installed the RCXs vertically so the robots can communicate using IR bounced off by the ceiling. The protocol was token based and it worked nicely. The play field was based on a greyscale mat with 6 inch walls. The only problem was locating the position on the play field, as the robots could not tell where they were sideways. Anyway, it didn’t work, but using a NXT kit it can definitely worth a try.