"Tony Hawk's Pro Skater" ("THPS") was released on the PlayStation in August 1999. Development of a sequel began immediately after its release. "Spider-Man" was also developed for Activision in 2000. Like "THPS", the technology for this game was based on the "Apocalypse" engine, which was in turn based on the "Big Guns" engine. Neversoft was now developing two major games in parallel, and expanded into two large teams. Activision acquired Neversoft in the summer of 1999 in a stock swap deal. The founders of Neversoft and several key employees signed four-year employment agreements.