NEW YORK (Reuters) – The Rubik’s Cube has delighted and confounded millions of players since Hungarian architecture professor Erno Rubik created it in 1974. Now the company that makes the twisting puzzle wants to stop the maker of Duncan yo-yos from selling an alleged knockoff.

Rubik’s Brand Ltd has sued Duncan Toys Co and the retailer Toys “R” Us to halt sales of a puzzle cube, which Duncan calls “Quick Cube,” that it said copies the world’s best-selling puzzle game.

According to the complaint filed on Monday night in U.S. District Court in Manhattan, Duncan’s 3X3 cube “mimics the features and overall appearance” of the Rubik’s Cube, mainly differing in its colors and “slight rounding” of the corners.

Rubik’s Brand, which is based in London, said this amounted to trademark infringement and unfair competition, and that Toys “R” Us was also liable for selling Duncan’s cubes.

“Consumers who expect to receive plaintiff’s Rubik’s Cube puzzle, for which plaintiff has developed a national and international reputation, will be disappointed when using defendants’ imitation,” which causes “irreparable harm” to Rubik’s Brand’s reputation and goodwill, the complaint said.

Toys “R” Us sells the Rubik’s Cube for $15.99 and Duncan’s Quick Cube for $4.99, according to its website.

Duncan spokesman Mike Burke on Tuesday said the allegations are without merit, and that the company intends to vigorously defend itself. Toys “R” Us did not immediately respond to requests for comment.

The lawsuit seeks to recoup alleged illegal profits and triple damages, and the destruction of unauthorized cubes.

Duncan is based in Middlefield, Ohio, and its parent, Baraboo, Wisconsin-based Flambeau Inc, is also a defendant. Toys “R” Us is based in Wayne, New Jersey.

Rubik’s Cube became a fad in the United States soon after its launch there in 1980, under a license to Ideal Toy Co, but remained on the market after demand fell. Roughly 100 million Rubik’s Cubes have been sold worldwide, the complaint said.