in 1979, is often considered the first such handheld video game console, as well as the first handheld to use interchangeable games, though the unit never caught on due to short-term technical struggles. Revolutionary at the time, the Microvision featured a 16x16 pixel LCD that a variety of games could be played by swapping out its faceplate, which contained the game's ROM data and controls. Nintendo's line of Game & Watch titles, first introduced in 1980, was based on inspiration from Gunpei Yokoi after seeing a man playing on an LCD calculation while passing time on a bullet train, and had devised the idea of an electronic game that doubled as a watch. Taking advantage of the technology used in the credit-card-sized calculators that had appeared on the market, Yokoi designed the series of LCD-based games to include a digital time display in the corner of the screen. While the Game & Watch series were considered handheld electronic games rather than handheld video game consoles, their success led Nintendo, through Yokoi's design lead, to produce the Game Boy in 1989, considered to be the defining basis of the current handheld game console. Console generations The history of video game consoles are typically segmented into "generations" which are used to group consoles that have shared a competitive market. These console generations typically last about five years, following a Moore's law progression where a rough aggregrate measure of processing power doubles every 18 months or increases ten-fold after five years. This cyclic market has resulted in an industry-wide adoption of the razorblade model in selling consoles at minimal profit margin while making revenue from the sale of games produced for that console, and then transitioning users to the next console model at the fifth year of the generation as the new generation comes on line, and thus incorporate planned obsolescence into the products to continue to bring consumers into the newer generations. However, the exact definition and delineation of console generations has not been consistently defined in the literature. Some schemes have been based on direct market data (including a seminal work published in an IEEE journal in 2002), while others are based on technology shifts. Wikipedia itself has been noted for creating its own version of console generation definitions that differ from other academic sources, the definitions from Wikipedia has been adopted by other sources but without having any true rationale