respectively to add elements of a strategy to what initially was a shooter game of pure reflexes. Russell had previously wanted to add gravity, but was unable to get the program to perform the calculations fast enough; Edwards optimized the drawing functions to free up processing time to calculate the effects of gravity. The initial version of the hyperspace function was limited to three jumps, but carried no risk save possibly re-entering the game in a dangerous position; later versions removed the limit but added the increasing risk of destroying the ship instead of moving it. Additionally, in March 1962, Saunders created gamepads for the game, to counter "Space War Elbow" from sitting hunched over the mainframe toggles. The game was a multiplayer-only game because the computer had no resources left over to handle controlling the other ship. Similarly, other proposed additions to the game such as a more refined explosion display upon the destruction of a spaceship and having the torpedoes also be affected by gravity had to be abandoned as there were not enough computer resources to handle them while smoothly running the game. One feature, having the speed and direction of torpedoes differ slightly with each shot, was added and then removed by Russell after player complaints. With the added features and changes in place, Russell and the other programmers shifted focus from developing the game to preparing to show it off to others such as at the MIT Science Open House at the end of April 1962. The group added a time limit, the hyperspace function, and a larger, second screen for viewers at the demonstration, and in May Graetz presented a paper about the game, "SPACEWAR! Real-Time Capability of the PDP-1", at the first meeting of the Digital Equipment Computer Users' Society. The demonstration was a success, and the game proved very popular at MIT; the laboratory that hosted the PDP-1 soon banned play except during lunch and after working hours. Visitors such as Frederik Pohl, the editor of Galaxy Science Fiction, enjoyed playing the "lovely game" and wrote that MIT was "borrowing from the science-fiction magazines", with players able to pretend to be Skylark characters. Beginning in mid-1962 and continuing over the next few years, members of the PDP-1 programming community at MIT, including Russell and the other Hingham Institute members, began to spread out to other schools and employers such as Stanford University