Once development on "Sonic 2" concluded, Cerny departed and was replaced by Roger Hector. STI was divided into two teams: the Japanese developers led by Naka, and the American developers. The Japanese began work on "Sonic the Hedgehog 3". "Sonic 3" was initially developed as an isometric game using the Sega Virtua Processor chip, but was restarted as a more conventional side-scrolling game after the chip was delayed. It introduced Sonic's rival Knuckles, created by artist Takashi Thomas Yuda. Due to an impending promotion with McDonald's and cartridges size constraints, the project was split in two: the first half, "Sonic 3", was released in February 1994, and the second, "Sonic & Knuckles", a few months later. The "Sonic & Knuckles" cartridge contains an adapter that allows players to connect it to "Sonic 3", creating a combined game, "Sonic 3 & Knuckles". "Sonic 3" and "Sonic & Knuckles", as with their predecessors, were acclaimed. To release a "Sonic" game in time for the 1993 holiday shopping season, Sega commissioned the American team to make a new game, the spin-off "Sonic Spinball". While "Spinball" received poor reviews, it sold well and helped build the reputation of its developers.