back and forth as players found ways to avoid the program—or simply turn it off, as the system had no security mechanism to prevent it. Project MAC was part of the nascent ARPANET, the precursor to the Internet, which connected several research institutions around America. Many of these institutions owned PDS-1 terminals, and Maze spread to them as well, allowing multiplayer games across the ARPANET. According to Lebling, the first multiplayer game between institutions was between students at MIT and the University of California, Santa Cruz, although the slow speed of the network left the non-MIT players at a disadvantage. The code for the game was adjusted by Harrenstien and Frankston to account for the extra network delay these cross-country games incurred. Maze was particularly popular at the University of Southern California and Stanford: it was later reported that at one point DARPA banned it from the network as half of the communication traffic between Stanford and MIT was for the game. The Maze Game and Mazewar Programmers have created several variants of the original Maze game. The first was partially developed by Thompson himself; in the fall of 1976 he took an electrical engineering digital electronics design class, in which he had to do a group project with Mark Horowitz and George Woltman. For the project, they created a hardware system that could run Maze titled "The Maze Game"; Thompson designed the computer hardware, Woltman wrote the software, and Horowitz created the display system. In this version, the maze was a 16 by 16 by 16 cube with no gravity in which the player could move up and down just as they did forward and back, as they found it easier to create hardware that did not need to treat the floor and ceiling differently than other sides. Woltman added robot players like in the computer version of the game, but the trio discovered that since humans found it difficult to visualize where they were in the multi-level maze, the robot players were much harder to beat despite their simple algorithm. They made the difficulty adjustable in response by letting the player adjust the hardware speed, in turn making the robots react slower. As the hardware could not use a computer monitor, the team used oscilloscopes that Horowitz made act as vector displays. After the class, the game remained as an example for future students for several years. In