Video game clone
A video game clone is either a video game or a video game console very similar to, or heavily inspired by, a previous popular game or console. Clones are typically made to take financial advantage of the popularity of the cloned game or system, but clones may also result from earnest attempts to create homages or expand on game mechanics from the original game. An additional motivation unique to the medium of games as software with limited compatibility, is the desire to port a simulacrum of a game to platforms that the original is unavailable for or unsatisfactorily implemented on. Legally, video game clones are not generally considered to be copyright infringement as mechanical elements are broadly uncopyrightable, an essential factor for creative development of new games based on past ideas. More recent case law has identified that game developers can protect their games' look and feel from clones, while methods like patents, trademarks, and industry regulation also help to fend off clones.
Cloning a game in digital marketplaces is common. It is hard to prevent and easy to compete with existing games. Developers can copyright the graphics, title, story, and characters, but have more difficulty protecting software design and game mechanics. A patent for the mechanics is possible but expensive and time-consuming. Popular game concepts often lead to that concept becoming incorporated or expanded upon by other developers. In other cases, games may be developed with clear influence from one or more earlier games. Such derivations are not always considered clones though the term may be used to make a comparison between games. As copyright law does not protect game mechanics, the reuse of such ideas is generally considered acceptable. For example, Grand Theft Auto III spurred a number of games that have been called GTA clones but which are not direct copies of assets or mechanical ideas. In these cases, games that are "clones" of another are generally not implied to have committed any intellectual property infractions, and otherwise considered legally acceptable practices, although calling such games clones is generally considered derogatory.
True video games clones occur when competitors, on seeing the success of a video game title, attempt to compete by creating a near-copy of the existing game with similar assets and gameplay with little additional innovation; developer Jenova Chen compared the nature of these clones similar to plagiarism in which there is little attempt to distinguish the new work from the original. Video game clones are seen by those developing them as low risk; knowing that a game or genre is popular, developing a clone of that game would appear to be a safe and quick investment, in contrast with developing a new title with unknown sales potential. Further, cloning of games from smaller developers, particularly indie developers, is more frequent as these small teams lack the financial resources to pursue legal recourse. Instead, these teams often appeal to social influence to try to have the cloner take corrective actions.
Hardware cloning (1970s–2000s)
Cloning of video games came early in the arcade video game industry shortly after the release of Pong by Atari in 1972. Its success led to numerous companies buying a copy of the arcade machine to try to make their own versions. Atari's Nolan Bushnell called these vendors "jackals", but took no legal action and instead focused on making new games to try to outpace them. Bushnell also maintained contractual agreements with Bally Manufacturing and Midway Manufacturing; in the case of Midway, Atari providing Midway with a licensed Pong design that Midway released as Winner.
One of those companies that had copied Pong was Allied Leisure, which had released its Paddle Battle arcade game in early 1973. When the market shifted from the two-player to four-player table tennis versions in mid-1973, Allied Leisure produced two new arcade games, Tennis Tourney and Ric-o-chet, both which Midway stated caused demand for the two-player Winner to drop dramatically. To stay competitive, Midway acquired one of Allied's games to compare the printed circuit board to that from Winner as to determine what was the new components for making it a four-player game, and added that to Winner's board, and released as Winner IV. Allied Leisure filed suit against Midway claiming copyright infringement of using its printed circuit board design in making Winner IV and unfair competition, but the judge failed to agree to a preliminary injunction, ruling that while a drawing of the printed circuit board may have copyright protection, the physical board itself would not and instead would be covered by patents, which were not involved in this case. The case was settled out of court in 1974 for undisclosed terms, believed due to factors relating to a short downturn in the market, as David Braun, the CEO of Allied Leisure had said in 1974 that "th[e] video game is yesterday's newspaper." The settlement was also likely due to pressure from the patent issues that had arisen around the home versions of Pong in the first generation of consoles that were occurring simultaneously.
The base ideas of a home video game console were developed by Ralph H. Baer while working at Sanders Associates, where in 1966 he began work on what ultimately became his "Brown Box" prototype. After securing approval of a proposal for his idea from his superiors, Baer worked with Sanders engineers Bill Harrison and Bill Rusch to execute its design while keeping it within a low cost target. By 1967, the optimized design was ready to be shopped to other manufacturers as Sanders was not in that market area. To protect the idea, Sanders applied for and received three patents in Baer's, Harrison's, and Rusch's names, covering their "television gaming apparatus"; this included the 1974 reissued U.S. Patent RE28,507 for a "television gaming apparatus", U.S. Patent 3,659,285 for a "television gaming apparatus and method", and U.S. Patent 3,728,480 for a "television gaming and training apparatus". Sanders eventually licensed the technology and the patents to Magnavox, which used it to make the Magnavox Odyssey, released in 1972. In 1974, Magnavox sued several companies on patent infringement for creating and distributing table-tennis arcade games including Atari and Midway. Atari settled in 1976 and agreed to pay Magnavox US$1,500,000 for a perpetual license to the three patents and other technology sharing agreements, allowing them to continue to release their home version of Pong. This case was ultimately decided in Magnavox's favor against the remaining defendants in early 1977.
However, just as with the arcade version, the home version of Pong drew a number of third-party hardware manufacturers to make Pong clones on the market, to a point where it was estimated that Atari's Pong console represented only about a third of sales of home Pong consoles. Magnavox continued to pursue action against these Pong clones using the three patents, estimated to have won over US$100 million in damages from suits and settlements through the lifetime of the patents. However, threats of lawsuits did not prevent more clones of the home console systems from being built, as these dedicated consoles were relatively risk free and easy to manufacture. This led to a flooded dedicated-game console market, and creating the industry's first market crash in 1977.:81–89
The original Atari Pong home console, labeled with Sears' "Tele-games" brand
Eventually, home consoles switched from built-in games to programmable microprocessor-based systems that operated from software stored in game cartridges within the second generation, making it more difficult to clone at the hardware level. However, off-brand manufacturers attempted to make bootleg copies of these consoles that has a similar form as the known console, but typically could only play built in games frequently on a liquid-crystal display (LCD). Other bootleg consoles would take the workings of older systems and repackage them in a newer housing that appears like the known consoles capable of playing the games from the original system. The latter was particularly true of consoles that attempted to clone the Nintendo Entertainment System (known as the Famicom system in Japan), which was not available in some countries in the Eastern European and Chinese regions, leading manufacturers within those nations to make numerous bootleg versions, knowing that it would be near-impossible for Nintendo to seek legal action against them.
The Pegasus, sold only in Eastern European states, was a Famicom clone though styled after the Super Famicom system
Software cloning (1980s–present)
While hardware itself became difficult to clone, the software of games were subsequently used in unlicensed copies for other systems. Cloning of arcade video games was popular during the arcade's "golden age" in the early 1980s. Arcade games, prior to mass production, were made in limited numbers for field testing in public spaces; once news got out that a new arcade game from industry leaders like Atari was out in the open, third-party competitors would be able to scope the game and rush to make a clone of the game, either as a new arcade game or for home consoles; an occurrence which happened with Missile Command in 1980. This ultimately diluted the market for new arcade games.
The most widely cloned arcade games in the early 1980s included Space Invaders (1978), Pac-Man (1980) and Donkey Kong (1981), clones of which were available for various different platforms by 1983; there were more than a hundred Space Invaders clones, at least 57 Pac-Man clones, at least 37 Frogger clones, and at least seventeen Donkey Kong clones by professional and amateur coders for platforms ranging from desktop microcomputers to graphing calculators. Nintendo estimated a loss of over $100 million to Donkey Kong clones on various different platforms despite attempts at litigation to stop them; the matter was further complicated by the Universal City Studios, Inc. v. Nintendo Co., Ltd. case where Universal Studios who claimed ownership over King Kong attempted to take action against Donkey Kong and its clones, notably the Tiger Electronics handheld electronic game King Kong, but the court ruled in Nintendo's favor along with ordering Tiger to pay damages to Nintendo.
BYTE reported in December 1981 that at least eight clones of Atari's arcade game Asteroids existed for personal computers. The magazine stated in December 1982 that that year "few games broke new ground in either design or format ... If the public really likes an idea, it is milked for all it's worth, and numerous clones of a different color soon crowd the shelves. That is, until the public stops buying or something better comes along. Companies who believe that microcomputer games are the hula hoop of the 1980s only want to play Quick Profit". The degree of cloning was so great that in 1981, Atari warned in full-page advertisements "Piracy: This Game is Over", stating that the company "will protect its rights by vigorously enforcing [its] copyrights and by taking appropriate action against unauthorized entities who reproduce or adapt substantial copies of ATARI games", like a home-computer clone.
Third parties continued to attempt or clone concepts or ideas from popular and successful games. Games like Tetris and Breakout inspired many games that used similar core concepts but expanded beyond that; the Breakout-inspired Arkanoid itself inspired many other clones that built upon its unique additions to Breakout. Gameplay elements of Street Fighter II and Mortal Kombat became common gameplay elements in the fighting game genre, A large number of games that tried to capitalize on the success of the 3D adventure game Myst were grouped as "Myst clones". Some video game genres are founded by archetypal games of which all subsequent similar games are considered derivatives; notably, early first-person shooters were often called "Doom clones", while the success of the open-world formula in Grand Theft Auto led to the genre of GTA clones. The genre of endless runners is based on the success and simplicity of the game Canabalt. Such cloning can also cause a relatively-sudden emergence of a new genre as developers attempt to capitalize on the interest. The battle royale genre grew rapidly after the success of PlayerUnknown's Battlegrounds and Fortnite Battle Royale across 2017 and 2018, while Dota Auto Chess released in January 2019 spawned several commercial games in the auto battler genre by mid-2019.
Another type of clone arose from developers in the modding, open source, and indie game communities, where these developers seek to recreate the mechanics of a popular title through reverse engineering, sometimes using their own original assets, and releasing the game typically for free and in homage to the original title. This allows the teams and users to expand upon original elements of the commercial game, such as software bugs that were not fixed, improving gameplay concepts, support for different and newer computers or console platforms, or adding new ideas to the base gameplay principles, as well as easing game extensions through user-created mods or add-ons. Some examples of these clones include Freeciv based on the Civilization series, Osu! based on Osu! Tatakae! Ouendan, and Frets on Fire based on Guitar Hero. The open source nature of these clones also enable new utilities, such as developing artificial intelligence agents that have learned and improved their play in Freeciv which in turn can help advance artificial intelligence research. Such games must be careful not to redistribute the original game's assets or they could face legal issues. OpenSC2K, an open-source recreation of SimCity 2000, was shut down by Electronic Arts after it was found that OpenSC2K used assets from SimCity 2000. One loophole is that some clones are or become engine recreations, faithful enough to directly use separately distributed assets from the original game by players who own it, such as GemRB, a clone of Baldur's Gate. Some of these games, may later incorporate code from the original game if it is relicensed, becoming a source port, as did OpenRA, a C&C:RA clone. For cloning of original indie games by other indie developers, while such practices do exist, indie developers tend to rely on an informal code of honor to shun those who do engage in cloning.
New concerns related to cloned video games came with the rise of social network and mobile games, typically which were offered as freemium titles to entice new players to play. The rising popularity of these games with casual players led to widespread clones. Zynga was one of the first major developers in social network games, and had long been criticized by the video game industry as cloning popular social and casual games from other developers, includes those of smaller developers without the resources to fight back in courts (as in the case of Tiny Tower by NimbleBit, which Zynga has cloned in their game, Dream Heights) or that are willing to settle out of court (as in the case of Zynga's Mafia Wars, which was accused of cloning David Maestri's Mob Wars). In August 2012, Electronic Arts (EA), via its Maxis division, put forth a lawsuit againstZynga, claiming that its Facebook game, The Ville was a ripoff of EA's own Facebook game, The Sims Social. The lawsuit challenges that The Ville not only copies the gameplay mechanics of The Sims Social, but also uses art and visual interface aspects that appear to be inspired by The Sims Social. Pundits have noted that EA, unlike these previous developers, are financially backed to see the case to completion; EA themselves have stated in the lawsuit that "Maxis isn’t the first studio to claim that Zynga copied its creative product. But we are the studio that has the financial and corporate resources to stand up and do something about it." The two companies settled out of court on undisclosed terms in February 2013.
Despite the Zynga case, clones of social and mobile games continued to flourish as the format gained popularity; the low cost, ease and simplicity of the tools needed to develop these made cloning in that sector a significant problem. For example, Flappy Bird had been cloned dozens of times due to programming code clearinghouses offering templated code to which others could easily add their own art assets. The creators of Threes! spent 14 months developing the game and tuning its mechanics, but the first clone was released 21 days after Threes! and the original was quickly overshadowed by 2048, a clone that was developed over a weekend. In the early period of social media games around 2012, Zynga had gained a negative reputation of making copycat clones in that space. However, according to their lead gameplay designer, Brian Reynolds, they see potential new genres and game ideas that gain popularity, and then strive to add their own innovation and concepts to at, so that "[their] goal is to have the highest-quality thing".
Another major area of concern for software clones arises within China. From 2000 to 2015, the Chinese government had numerous restrictions on imports of hardware and software, and access to non-Chinese storefronts. While this allowed gaming on personal computers to flourish within China, the cost of acquiring both hardware and software was too expensive for many, leading to Chinese developers to create low-cost clones of popular Western and Japanese titles for the Chinese market, which persist today. Foreign companies are faced with difficulties in seeking legal action against the Chinese developers that have created these clones, making cloning a far less risky process. Thus, it is common for popular games from both Western and Japanese markets to see near-exact clones appear within China, often within weeks of the original game's release. A notable example is a clone of Blizzard Entertainment's Hearthstone called Sleeping Dragon: Heroes of the Three Kingdoms created by Chinese developer Unico, released within a few months of Hearthstone's beta release. Blizzard was ultimately successful in suing Unico for US$1.9 million in damages in 2014. In other cases, clones are made to address elements of the original game that are unsuitable under China's content restriction laws; for example, Tencent, which operated the publishing of PlayerUnknown's Battlegrounds in China, was forced to pull the game due to content related to violence and terrorism, and instead replaced it with a clone, Game for Peace, which otherwise reused assets from Battlegrounds but removed blood and gore.
Video game clones are generally difficult to prevent through intellectual property laws such as copyright, patents, or trademarks. The game industry has generally been built on the concept of building atop gameplay concepts from other developers to make novel games, but avoiding outright copying element for element as to make a direct clone. Broadly, video games lack a fixed medium, and fall into the same area as software copyright where underlying source code as well as art and other assets quality for copyright, but the gameplay does not. In the United States specifically, video games fall into the idea-expression distinction, that one cannot copyright the underlying gameplay but can copyright a specific implementation of it. Case law until 2012 has generally favorable to clones, often ruling that clones of a game do not violate copyright since they meet scènes à faire principle, elements necessary for a specific theme of a game.
However, in two separate U.S. cases in 2012, Tetris Holding, LLC v. Xio Interactive, Inc. and Spry Fox, LLC v. Lolapps, Inc., courts found using the Abstraction-Filtration-Comparison test that clones that not only copy gameplay without excessive changes but also too much of the original game's look and feel were in violation of copyright law. This new approach gave developers a better means to fight against direct clones.
Patents have been used in a limited fashion to protect novel gameplay ideas, such as the navigation system in Sega's Crazy Taxi games. Sega sued Fox Interactive for patent infringement for their use of a similar system in The Simpsons: Road Rage, a case that was ultimately settled out of court. Trademarks have also been used in a very limited fashion to block other developers from using the same terminology for their games or gameplay.
More recently, with the popularity of social and mobile game stores like Apple's App Store for iOS system and Google Play for Android-based systems, a large number of likely-infringing clones have begun appearing. While such storefronts typically include a review process before games and apps can be offered on them, these processes do not consider copyright infringement of other titles. Instead, they rely on the developer of the work that has been cloned to initiate a complaint regarding the clone, which may take time for review. The cloned apps often are purposely designed to resemble other popular apps by name or feel, luring away purchasers from the legitimate app, even after complaints have been filed. Apple has released a tool to streamline claims of app clones to a team dedicated to handle these cases, helping to bring the two parties together to try to negotiate prior to action. While Apple, Google, and Microsoft took steps to stem the mass of clones based on Swing Copters after its release, experts believe it is unlikely that these app stores will institute any type of proactive clone protection outside of clear copyright violations, and these experts stress the matter is better done by the developers and gaming community to assure the original developer is well known, protects their game assets on release, and gets the credit for the original game.
Valve, which operates the Steam digital storefront for games on personal computers, also takes steps to remove games that are clearly copyright-infringing clones of other titles on the service, once notified of the issue.
- Chen, Brian X. (March 11, 2012). "For Creators of Games, a Faint Line on Cloning". The New York Times. Retrieved September 6, 2019.
- "Hunt for Grand Theft Auto pirates". BBC News. 2004-10-21. Retrieved 2008-08-26.
- Calixto, Joshua (April 20, 2016). "The False Legacy Of Grand Theft Auto 3". Killscreen. Retrieved September 6, 2019.
- Webster, Andrew (2009-12-06). "Cloning or theft? Ars explores game design with Jenova Chen". Ars Technica. Retrieved 2015-10-20.
- Kelly, Tadhg (2014-01-05). "Why all the Clones". TechCrunch. Retrieved 2015-10-20.
- Kent, Steven (2001). "The Jackals". Ultimate History of Video Games. Three Rivers Press. pp. 60–61. ISBN 0-7615-3643-4.
- Ford, William (2012). "Copy Game for High Score: The First Video Game Lawsuit". Journal of Intellectual Property Law. 20 (1): 1–42. Retrieved August 4, 2020.
- "Meet the video games godfather: Ralph Baer". The Guardian. Archived from the original on December 22, 2015. Retrieved December 13, 2015.
- Smith, Alexander (2015-11-16). "1TL200: A Magnavox Odyssey". They Create Worlds. Archived from the original on 2016-02-02. Retrieved 2016-04-25.
- US patent RE28,507, Rouch, William, "Television gaming apparatus", issued August 5, 1975
- US patent 3,659,285, Baer, Ralph; William Rouch & William Harrison, "Television gaming apparatus and method", issued April 25, 1972
- US patent 3,728,480, Baer, Ralph, "Television gaming and training apparatus", issued April 17, 1973
- "Magnavox Game Suit". Weekly Television Digest, with Consumer Electronics. December 13, 1976. p. 13.
- Kent, Steven (2001). "The King and Court". Ultimate History of Video Games. Three Rivers Press. p. 58. ISBN 0-7615-3643-4.
- Kent, Steven (2001). "And Then There Was Pong". Ultimate History of Video Games. Three Rivers Press. pp. 45–48. ISBN 0-7615-3643-4.
- "Magnavox Patent". The New York Times. 1982-10-08. Archived from the original on 2016-03-04. Retrieved 2007-02-25.
- "Magnavox Settles Its Mattel Suit". The New York Times. 1983-02-16. Archived from the original on 2016-03-13. Retrieved 2007-02-25.
- Mullis, Steve (2014-12-08). "Inventor Ralph Baer, The 'Father Of Video Games,' Dies At 92". National Public Radio. Archived from the original on 2016-03-22. Retrieved 2016-05-03.
- Clark, Pamela (December 1982). "The Play's the Thing". BYTE. p. 6. Retrieved 19 October 2013.
- Herman, Leonard (2012). "Ball-and-Paddle Controllers". In Wolf, Mark J.P. (ed.). Before the Crash: Early Video Game History. Wayne State University Press. ISBN 978-0814337226.
- Jensen, K. Thor (August 8, 2016). "8 Super Weird Bootleg Game Consoles". PC Magazine. Retrieved September 5, 2019.
- Plunkett, Luke (November 4, 2011). "The Wonderful, Shady World of Knock-Off Nintendo Consoles". Kotaku. Retrieved September 5, 2019.
- Jou, Eric (February 5, 2014). "A Brief History of Chinese Game Consoles". Kotaku. Retrieved September 5, 2019.
- Rubens, Alex (August 15, 2013). "The Creation Of Missile Command And The Haunting Of Its Creator, Dave Theurer". Polygon. Retrieved September 5, 2019.
- "Gorilla Keeps on Climbing! Kong". Computer and Video Games. No. 26 (December 1983). 16 November 1983. pp. 40–1.
- Grace, Lindsay (June 19, 2018). "The Original 'Space Invaders' Is a Meditation on 1970s America's Deepest Fears". Smithsonian Magazine. Retrieved April 22, 2021.
- Hague, James (April 13, 2021). "The Giant List of Classic Game Programmers". Dadgum. Retrieved 20 April 2021.
- Altice, Nathan (2015). "Chapter 2: Ports". I Am Error: The Nintendo Family Computer / Entertainment System Platform. MIT Press. pp. 53–80. ISBN 9780262028776.
- Kent, Steven L. (2001). The Ultimate History of Video Games: From Pong to Pokémon and Beyond- The Story behind the Craze that Touched Our Lives and Changed the World. Roseville, California: Prima Publishing. p. 217. ISBN 0-7615-3643-4.
- Williams, Gregg (December 1981). "Battle of the Asteroids". BYTE. pp. 163–165. Retrieved 12 August 2015.
- "Atari Software / Piracy: This Game is Over". BYTE (advertisement). October 1981. p. 347. Retrieved 16 March 2016.
- Nelson, Mark. "Breaking Down Breakout: System And Level Design For Breakout-style Games". Gamasutra. Retrieved 2007-11-29.
- Patterson, Eric L. (November 3, 2011). "EGM Feature: The 5 Most Influential Japanese Games Day Four: Street Fighter II". Electronic Gaming Monthly. Retrieved 17 April 2012.
- "How hackers reinvented Street Fighter 2". Eurogamer.net. 21 February 2014. Retrieved 10 December 2015.
- Scott Patterson. "Innovation Has Never Been the Cornerstone of the Video Game Industry". Kotaku. Gawker Media. Retrieved 10 December 2015.
- Parrish, Jeremy. "When SCUMM Ruled the Earth". 1UP.com. Archived from the original on February 29, 2016. Retrieved May 2, 2008.
- Turner, Benjamin & Bowen, Kevin, Bringin' in the DOOM Clones, GameSpy, December 11, 2003, Accessed February 19, 2009
- Parkin, Simon (2013-06-07). "Don't Stop: The Game That Conquered Smartphones". New Yorker. Retrieved 2015-10-20.
- Fillari, Alessandro (May 26, 2018). "Battle Royale Games Explained". GameSpot. Archived from the original on May 26, 2018. Retrieved May 26, 2018.
- Gilroy, Joab. "An Introduction to Auto Chess, Teamfight Tactics and Dota Underlords". IGN. Archived from the original on July 4, 2019. Retrieved July 10, 2019.
- Grayson, Nathan. "A Guide To Auto Chess, 2019's Most Popular New Game Genre". Kotaku. Archived from the original on July 3, 2019. Retrieved July 21, 2019.
- Schramm, Mike (May 15, 2013). "FreeCiv now playable in browsers, including on iOS devices". Engadget. Retrieved September 6, 2019.
- Carpenter, Nicole (2019-07-16). "Gamers with godlike reflexes are racing to break world records in this rhythm game". PC Gamer. Retrieved 2019-08-12.
- Stubbs, Mike (May 1, 2018). "The spirit of Guitar Hero lives on in a bizarre community-made clone". Eurogamer. Retrieved September 6, 2019.
- Etherington, Darrell (December 6, 2016). "Arago's AI can now beat some human players at complex civ strategy games". TechCrunch. Retrieved September 6, 2019.
- Chalk, Andy (July 31, 2018). "EA takes down open source SimCity 2000 remake for using copyrighted assets". PC Gamer. Retrieved September 6, 2019.
- Phillips, Tom (2015). ""Don't clone my indie game, bro": Informal cultures of videogame regulation in the independent sector". Cultural Trends. 24 (2): 143–153. doi:10.1080/09548963.2015.1031480. S2CID 145650507.
- Glasser, AJ (2011-07-27). "Clone Wars: What Copycats Really Do To The Social Games Industry". Adweek. Retrieved 2015-10-20.
- Kelly, Tadhg (2012-08-04). "Zyngapocalypse Now (And What Comes Next?)". TechCrunch. Retrieved 2012-08-07.
- Kelly, Tadhg (2009-12-18). "Zynga and the End of the Beginning". Gamasutra. Retrieved 2012-08-07.
- Griffen, Daniel Nye (2012-08-06). "EA Sues Zynga, But Deeper Social Issues Threaten". Forbes. Retrieved 2012-08-07.
- Brown, Nathan (2012-01-25). "How Zynga cloned its way to success". Edge. Retrieved 2012-08-07.
- Jamison, Peter (2010-09-08). "FarmVillains". SF Weekly. Retrieved 2012-08-07.
- Tassi, Paul (2012-08-03). "Zynga Pokes a Giant: EA Files Lawsuit After The Ville Clones The Sims". Forbes. Retrieved 2012-08-07.
- Cifaldi, Frank (2013-02-15). "EA and Zynga settle The Ville copycat case out of court". Gamasutra. Retrieved 2013-02-15.
- Tassi, Paul. "Over Sixty 'Flappy Bird' Clones Hit Apple's App Store Every Single Day".
- Batchlor, James (2014-08-21). "Flappy Bird creator's new game Swing Copters has already been cloned. A lot". Develop. Retrieved 2014-08-21.
- Rigny, Ryan (2014-03-05). "How to Make a No. 1 App With $99 and Three Hours of Work". Wired. Retrieved 2014-03-05.
- Renaudin, Clement (2014-03-27). "Cloned to Death: Developers Release all 570 Emails That Discussed the Development of 'Threes!'". Touch Arcade. Retrieved 2014-03-28.
- "THREES - A tiny puzzle that grows on you". asherv.com.
- Takahashi, Dean (January 31, 2012). "Zynga CEO: We aren't the copycats on Bingo social game". Venture Beat. Retrieved September 11, 2019.
- Graft, Kris (January 31, 2012). "Talking Copycats with Zynga's Design Chief". Gamasutra. Retrieved September 11, 2019.
- Messner, Steven (May 23, 2019). "Censorship, Steam, and the explosive rise of PC gaming in China". PC Gamer. Retrieved May 23, 2019.
- Snyder, Matt (May 17, 2018). "China's Digital Game Sector" (PDF). United States-China Economic and Security Review Commission. Retrieved September 6, 2019.
- Goh, Brenda; Jiang, Sijia (May 7, 2019). "Tencent pulls blockbuster game PUBG in China, launches patriotic alternative". Reuters. Retrieved September 6, 2019.
- Lampros, Nicholas M. (2013). "Leveling Pains: Clone Gaming and the Changing Dynamics of an Industry". Berkeley Technology Law Journal. 28: 743.
- Lunsford, Christopher (Fall 2013). "Drawing a Line between Idea and Expression in Videogame Copyright: The Evolution of Substantial Similarity for Videogame Clones". Intellectual Property Law Bulletin. 18 (1): 87–118.
- Sirlin, David (2007-02-27). "The Trouble With Patents". Gamasutra. Retrieved 2012-08-07.
- Dredge, Stuart (2012-02-03). "Should Apple take more action against march of the iOS clones?". The Guardian. Retrieved 2012-08-10.
- Epsom, Rip (2011-12-11). "Can We Stop The Copycat Apps?". TechCrunch. Retrieved 2012-08-10.
- Constine, John (2012-02-03). "Apple Kicks Chart Topping Fakes Out Of App Store". TechCrunch. Retrieved 2012-08-10.
- Foresman, Chris (2012-09-04). "Apple now provides online tool to report App Store ripoffs". Ars Technica. Retrieved 2012-09-04.
- Batchelor, James (2014-09-05). "Experts explain difficulties in policing mobile marketplaces". Develop. Retrieved 2014-09-05.
- Li, Zihao (Spring 2019). "The Copyright Protection of Video Games from Reskinning in China - A Comparative Study on UK, US and China Approaches". Tsinghua China Law Review. 11 (2): 293–340.
- Wilde, Tyler (September 26, 2017). "Valve removes 173 'spam' games from Steam, all published by one person". PC Gamer. Retrieved September 6, 2019.