Nintendo released the Game Boy in Japan on 21 April 1989, designed under the direction of Gunpei Yokoi and the Nintendo Research & Development 1 team. It used a 160 × 144-pixel monochrome LCD screen and interchangeable cartridges known as Game Paks. Unlike contemporary handheld systems that opted for colour displays, Nintendo prioritised size, battery life and cost. The Game Link cable allowed two units to be connected for compatible games. Tetris played a fundamental role in its international launch and demonstrated that a cartridge-based handheld could sustain a software library conceptually comparable to that of a home console.