Thompson showed him, it was soon re-added as the pair greatly expanded the game. The new version of the game used the PDP-10 as a centralized server and supported up to eight players or computer-controlled figures in a maze at once, which was now a 16 by 32 grid. Thompson worked on the PDS-1 code that allowed for more players, the visuals for the bullets, the score-keeping, the ability to see a top-down view of the maze, and a cheat command to move through walls. Lebling, meanwhile, wrote the PDP-10 code to connect all of the players and allow text messaging between terminals, a simple "robot" player that could play the game if there were not enough human players, and a program for players to create their own maze layouts. When he discovered that the robot players were too difficult for some players, he altered the robot players to move slower once they scored a certain number of points. Players were represented in the maze as their three-letter user id, along with an arrow pointing which way they were facing. The game was popular around the lab as well as with other MIT students, who would make accounts on the system just to play Maze. As users had to reserve time on the terminals due to the limited availability, some players would go to the lab in the middle of the night in order to play the game. According to Lebling, Maze was played almost constantly outside of the primary lab hours. Once Thompson and Lebling converted the game to the PDP-10, other programmers further developed the Maze code. Ken Harrenstien and Charles Frankston rewrote portions of the game to use fewer resources so that the PDP-10 could run more than one instance of the game at the same time. Another researcher, Tak To, wrote a "Maze Watcher" program that ran on an Evans & Sutherland LDS-1 terminal and would display a top-down view of the maze and players in a Maze game for onlookers. Although lab director J. C. R. Licklider and assistant director Al Vezza also played the game, as the lab was funded for serious purposes by the Defense Advanced Research Projects Agency (DARPA) they attempted to limit use of the program. At Vezza's request, Lebling created a "Maze Guncher" program that would run in the background and crash any running Maze games, leading to a continual