Nintendo produced its own version for the NES as well as a version for the Game Boy. Both versions were commercially successful and Nintendo held the "Tetris" license for many years. With fewer than 100,000 copies known to exist, the Tengen release has since become a collector's item, due to its short time on the market. Various publications have since noted that Tengen's "Tetris" was in some ways superior to the official NES release, especially since the Tengen game featured a two-player simultaneous mode not available in Nintendo's version.