Besides handling the rights and distribution for every official version of Tetris, The Tetris Company is also responsible for protecting the Tetris brand from unlicensed knock-offs. In the recent past, it's done this by forcing platform holders like Apple to remove unofficial copies of the game from the iOS App Store as soon as they pop up, for instance.
-But the company went a little farther further in the case of iPhone Tetris clone Mino, taking developer Xio Interactive to court to protect the Tetris copyright. A New Jersey circuit court judge recently ruled in favor of The Tetris Company in that case, issuing a ruling that highlights the legal challenges in determining what separates a hackneyed clone from a game that is merely "inspired" by an existing title.
While game designers usually have a pretty easy time telling when their game design has been ripped off by a clone, proving actual copyright infringement in court is usually an uphill battle. That's because copyright law doesn't actually protect the basic idea and underlying rules of a game, which need a duly filed and approved patent to be locked down. The copyright on a game only protects the "expression" of those rules, which usually covers things like character art, music and sound effects. That makes it relatively easy for a clone to mimic the successful engine of a game while making just enough changes on the surface to avoid a successful legal challenge.
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