Game Genie

The Game Genie is a series of cheat systems designed by Codemasters and sold by Camerica and Galoob for the Mega Drive, Sega Genesis and Game Gear that modifies game data, allowing the player to cheat, manipulate various aspects of games, and sometimes view unused content and functions. It is known as the first example of consumer-friendly "game enhancement" by means of (temporarily) directly altering the binary code of a game. Although there are currently no Game Genie products on the market, over 5 million units have been sold worldwide, and most video game console emulators feature Game Genie support. Emulators that have Game Genie support also allow a near-unlimited number of codes to be entered, whereas the actual products have a much smaller limit that usually tops between three and six codes. The Action Replay, Code Breaker, and GameShark are similar hacking devices, some acting as a spiritual successor on later generation consoles, although they were created by entirely different companies.

Operation and design
The Game Genie attaches to the end of a cartridge and is then inserted into the cartridge port of the console for which it was designed. The addition of the Game Genie causes the cartridge to protrude from the console when fully inserted, making the depression impossible. Therefore, the Game Genie was designed in such a way that it did not need to be depressed in order to start the game.

Upon starting the console, the player may enter a series of characters referred to as a "Cheat codes" or several such series that reference addresses in the ROM of the cartridge. Each code contains an integer value that is read by the system in place of the data actually present on the cartridge.

Because the Game Genie patches the program code of a game, the codes are sometimes referred to as patch codes. These codes can have a variety of effects. The most popular codes give the player some form of invulnerability, infinite ammunition, level skipping, or other modifications that allow the player to be more powerful than intended by the game developers. In rare cases, codes even unlock hidden game features that developers had scrapped and rendered unreachable in normal play. Nonetheless, inputting a random code is as effective as using PEEK and POKE operations randomly. The results can yield a useful code, but will most likely result in anything from a mundane or highly unnoticeable change to freezing the game and possibly corrupting saved data.

The Game Genie's innovations are covered by U. S. Patent #5112051, "Interfacing device for a computer games system", filed May 30, 1990. This patent expired on May 30, 2010 according to current US patent law.

Sega Game Gear
The Sega Game Gear's Game Genie had a more complicated design than those for other systems. When inserted into the cartridge slot, another slot would pop up to insert the Game Gear cartridge. It also had a compartment which contained a book of codes. The codes were printed on sticky labels to put on the back of the Game Gear cartridge. When entering codes, the player could easily see what to type in rather than looking through the book.

On the screen in which a code is entered for the Game Gear Game Genie, a player typing the word "DEAD" will cause the screen to move up and down, possibly as an Easter egg.

Sega Genesis
On the Sega Genesis, the Game Genie can function as a country converter cartridge since most of these games are only regional locked to their respective regions by the shape of the cartridges and a set of a few bytes in the header of the ROM.

Controls (Genesis version)

 * Move “Swirling Star” cursor–D-Pad or joystick
 * Erase a letter in code–move Swirling Star on letter, press C button
 * Change letter–hold B button while moving Star, release B button on letter, press A button for new letter
 * Erase one code–position Star on any letter in code, hold B and C buttons for a few seconds
 * Erase all codes–press buttons A-C for a few seconds

Creating own codes (Genesis version)
Although not all codes will work, changing either the sixth character and/or the first and second characters in a code could create a custom code.

Updates throughout the years
The Game Genie was usually sold with a small booklet of discovered codes for use with the system. However, these booklets would eventually become obsolete as new codes were discovered and new games were released that were not covered. To address this, an update system was implemented, where subscribers would receive quarterly booklet updates or buy them individually for $1.50 U. S. each. Some of the codes were also later reported as to being problems or not working at all (for instance, in the volume one, first issue of these booklets, it reported that some codes for Sonic the Hedgehog would not work when the player started games on special stages using Code 13). In addition, Galoob also ran ads in certain gaming publications GamePro that featured codes for newer games. Today, these codes and many others discovered by players can be found for free online.

There was also a second version of the Game Genie created for the Genesis in 1994, which came in much smaller packaging (the original box and printed instructions were a lot bigger), having some of the newer games since the first addition came out as well as some of the older games' codes left out of the booklet, such as Star Control, Starflight and Ultimate Qix, as a few of several examples. However, even though not mentioned in the booklet, codes for those games still worked with the unit though, along with others that were left out.

Distribution in the UK
Distribution of the Game Genie product in the UK was handled by Hornby Hobbies, usually associated with model railways and the Scalextric brand. Working closely with Codemasters, they were also responsible for setting up a dedicated telephone helpline to cater for the ever increasing need for newer codes required to cheat/enhance the latest games. This service was manned by the Game Genie Guru of the early 90s, Mark Stoneham, who also regularly featured in console magazines listing his latest collection of up-to-date codes and making the odd guest appearance on Channel 4's GamesMaster and Sky's Games World.