hardware as the console type, but put inside a keyboard instead of a console lookalike. They are usually supplied with a cartridge containing some computer-style software, such as a simple word processor and a version of BASIC (most common are G-BASIC, a counterfeit version of Family BASIC, and F-BASIC, an original but more limited version), and some "educational" typing and mathematics games. Some even include a computer mouse and a GUI-style interface. Note that, while the interface is similar to Nintendo's Family BASIC keyboard, clone keyboards are generally not fully compatible with official software (and vice versa) due to differing key layouts. Software game titles Since none of these unlicensed clones contain the 10NES authentication chip, most are capable of running games which an official NES model would not run. In addition, many modern NES clones come with a built-in selection of games, typically stored on an internal ROM which can range from 128 KB up to several megabytes in size. These built-in games are usually designed to complement, rather than replace, the traditional cartridge slot, although some devices omit such a slot entirely, allowing only the built-in games to be played. Typical numbers for the built-in "distinct" games range from as low as three to as high as fifty or one hundred games for more expensive products. The number of "distinct games" is important, because while many NES clones claim to have thousands of built-in games, most of these games are usually nothing more than hacks that allow the player to start the same game at different levels or with different numbers of lives. The games are usually direct unlicensed copies of official NES and Famicom game titles, usually with copyright information removed and sometimes featuring other minor changes. The most commonly found games in NES clones are generally games below 64 K of ROM size and which can be easily split into distinct subgames or levels. As such, Track & Field and Circus Charlie are present in a large percentage of NES clones, usually blown up to count as 6 or 7 "distinct" games each. Duck Hunt (often with its clay shooting mode shown as a separate game) is also a common NES clone feature as they justify the existence of the light gun accessory. Other popular, although less common choices, are Super Mario Bros. hacks, Excitebike, Tetris, Magic Jewelry (an unlicensed clone of Columns), older sports titles