The founders of id Software met in the offices of Softdisk developing multiple games for Softdisk's monthly publishing, including "Dangerous Dave". In September 1990, John Carmack developed an efficient way to rapidly side-scroll graphics on the PC. Upon making this breakthrough, Carmack and Tom Hall stayed up late into the night making a replica of the first level of the popular 1988 NES game "Super Mario Bros. 3", inserting stock graphics of John Romero's Dangerous Dave character in lieu of Mario. When Romero saw the demo, entitled "Dangerous Dave in Copyright Infringement", he realized that Carmack's breakthrough could have potential. The team that would later form id Software immediately began moonlighting, going so far as to "borrow" company computers that were not being used over the weekends and at nights while they designed their own remake of "Super Mario Bros. 3".