Missing Link is a mechanical puzzle invented in 1981 by Steven P. Hanson and Jeffrey D. Breslow.
The puzzle has four sides, each depicting a chain of a different color. Each side contains four tiles, except one which contains three tiles and a gap. The top and bottom rows can be rotated, and tiles can slide up or down into the gap. The objective is to scramble the tiles and then restore them to their original configuration.
The two middle rows cannot be rotated. To move tiles in these rows, you need to loop the tiles from one row to another, up and down.
There are 15 tiles and a gap, giving a maximum of 16! arrangements. However, the middle tiles of each four-tile chain are identical, and each position is equivalent to seven other positions obtained by rotating the entire puzzle (about its axis or upside-down), reducing the number of arrangements to 16! / 8 / 8 = 326,918,592,000. If the three long chains are also considered interchangeable, then the number of arrangements is further reduced to 16! / 8 / 8 / 6 = 54,486,432,000.
Monosaccharides, also called simple sugar, are the simplest form of sugar and the most basic units of carbohydrates. They cannot be further hydrolyzed to simpler chemical compounds. The general formula is C nH 2nO n. They are usually colorless, water-soluble, and crystalline solids. Some monosaccharides have a sweet taste.
Pentomino tiling puzzles and games are popular in recreational mathematics. Usually, video games such as Tetris imitations and Rampart consider mirror reflections to be distinct, and thus use the full set of 18 one-sided pentominoes.
Rubik's Cube is a 3-D combination puzzle invented in 1974 by Hungarian sculptor and professor of architecture Ernő Rubik. Originally called the Magic Cube, the puzzle was licensed by Rubik to be sold by Ideal Toy Corp. in 1980 via businessman Tibor Laczi and Seven Towns founder Tom Kremer and won the German Game of the Year special award for Best Puzzle that year. As of January 2009, 350 million cubes had been sold worldwide, making it the world's top-selling puzzle game. It is widely considered to be the world's best-selling toy.
SameGame (さめがめ) is a tile-matching puzzle originally released under the name Chain Shot! in 1985 by Kuniaki Moribe (Morisuke). It has since been ported to numerous computer platforms, handheld devices, and even TiVo, with new versions as of 2016.
The Rubik's Revenge is a 4×4×4 version of Rubik's Cube. It was released in 1981. Invented by Péter Sebestény, the Rubik's Revenge was nearly called the Sebestény Cube until a somewhat last-minute decision changed the puzzle's name to attract fans of the original Rubik's Cube. Unlike the original puzzle, it has no fixed facets: the centre facets are free to move to different positions.
Rubik's Magic, like Rubik's Cube, is a mechanical puzzle invented by Ernő Rubik and first manufactured by Matchbox in the mid-1980s.
The 15-puzzle is a sliding puzzle that consists of a frame of numbered square tiles in random order with one tile missing. The puzzle also exists in other sizes, particularly the smaller 8-puzzle. If the size is 3×3 tiles, the puzzle is called the 8-puzzle or 9-puzzle, and if 4×4 tiles, the puzzle is called the 15-puzzle or 16-puzzle named, respectively, for the number of tiles and the number of spaces. The object of the puzzle is to place the tiles in order by making sliding moves that use the empty space.
The Professor's Cube is a combination puzzle, a 5×5×5 version of the Rubik's Cube. It has qualities in common with both the original 3×3×3 Rubik's Cube and the 4×4×4 Rubik's Revenge, and knowing how to solve either can help when working on the 5×5×5 cube.
The Pyraminx is a regular tetrahedron puzzle in the style of Rubik's Cube. It was made and patented by Uwe Mèffert after the original 3 layered Rubik's Cube by Erno Rubik, and introduced by Tomy Toys of Japan in 1981.
Rubik's Clock is a mechanical puzzle invented and patented by Christopher C. Wiggs and Christopher J. Taylor. The Hungarian sculptor and professor of architecture Ernő Rubik bought the patent from them to market the product under his name. It was first marketed in 1988.
The Square-1, also known as Back to Square One and Cube 21, is a puzzle similar to the Rubik's Cube. Its distinguishing feature among the numerous Rubik's Cube variants is that it can change shape as it is twisted, due to the way it is cut, thus adding an extra level of challenge and difficulty. The Super Square One and Square Two puzzles have been recently introduced. The Super Square One has two additional layers that can be scrambled and solved independently of the rest of the puzzle, and the Square Two has extra cuts made to the top and bottom layer, making the edge and corner wedges the same size.
Zoo Keeper is a tile-matching puzzle video game developed for the Web by Robot Communications and later ported to the Nintendo DS by Japanese video game publisher Success. Zoo Keeper was released for arcades in 2004. The game was then brought to American and European shores by Ignition Entertainment, and has since been released for iOS and Android devices under the title Zookeeper DX Touch Edition by Kiteretsu.
The V-Cube 6 is a 6×6×6 version of Rubik's Cube. The first mass-produced 6×6×6 was invented by Panagiotis Verdes and is produced by the Greek company Verdes Innovations SA. Other such puzzles have since been introduced by a number of Chinese companies, some of which have mechanisms which improve on the original. Unlike the original puzzle, it has no fixed facets: the center facets are free to move to different positions.
The V-Cube 7 is a combination puzzle in the form of a 7×7×7 cube. The first mass-produced 7×7×7 was invented by Panagiotis Verdes and is produced by the Greek company Verdes Innovations SA. Other such puzzles have since been introduced by a number of Chinese companies, some of which have mechanisms which improve on the original. Like the 5×5×5, the V-Cube 7 has both fixed and movable center facets.
The Pyraminx Crystal is a dodecahedral puzzle similar to the Rubik's Cube and the Megaminx. It is manufactured by Uwe Mèffert and has been sold in his puzzle shop since 2008.
The Void Cube is a 3-D mechanical puzzle similar to a Rubik's Cube, with the notable difference being that the center pieces are missing, which causes the puzzle to resemble a level 1 Menger sponge. The core used on the Rubik's Cube is also absent, creating holes straight through the cube on all three axes. Due to the restricted volume of the puzzle it employs an entirely different structural mechanism from a regular Rubik's Cube, though the possible moves are the same. The Void Cube was invented by Katsuhiko Okamoto. Gentosha Education, in Japan, holds the license to manufacture Void Cubes.
The Helicopter Cube is a Rubik's Cube-like puzzle invented by Adam G. Cowan in 2005 and built in 2006. It is also in the shape of a cube. At first glance, the Helicopter Cube may seem like a combination of the 2x2x2 and the Skewb, but it actually cuts differently, and twists around cube edges rather than cube faces. The purpose of the puzzle is to scramble the colors, and then restore them back to their original state of a single color per face.
Alexander's Star is a puzzle similar to the Rubik's Cube, in the shape of a great dodecahedron.
The V-Cube 8 is an 8×8×8 version of the Rubik's Cube. Unlike the original puzzle, it has no fixed facets: the center facets are free to move to different positions. The design was covered by Panagiotis Verdes' patent from 2007 but Verdes Innovations SA did not produce it for sale until 2014. Other 8×8×8 cubes are produced by the Chinese companies ShengShou, MoYu, and YuXin.
The Gear Cube is a 3-D combination puzzle designed and created by Dutch puzzle maker Oskar van Deventer. It was initially produced by Shapeways in 2009 and known as "Caution Cube" due to the likeliness of getting fingers stuck between the gears while speedcubing. Later, in 2010, it was mass-produced by Meffert's as the "Gear Cube".
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