I was lucky enough to visit Dynamicland at one point. The computing environment they had set up there was interesting. Programs are stored on a central server, but are executed by putting a printout of the code (with colored dots around the edges serving as a barcode) on a tabletop that has a camera and a projector above it. I/O between programs happens by putting cards next to each other. The programs also affect what the projector displays on the board, but the only persistent state is the presence and position of cards on the table.