This article has multiple issues. Please help improve it or discuss these issues on the talk page. (Learn how and when to remove these template messages)(Learn how and when to remove this template message)
Speedcubing (also known as speedsolving) is the activity of solving a variety of twisty puzzles, the most famous being the Rubik's Cube, as quickly as possible. For most puzzles, solving entails performing a series of moves that alters a scrambled puzzle into a state in which every face of the puzzle is a single, solid color. Some puzzles have different requirements to be considered solved, such as the Clock, for which all the dials must be moved into the 12 'o clock position.
Most cubes are sold commercially in variations of 2×2×2, 3×3×3, 4×4×4, 5×5×5, 6×6×6, and 7×7×7, although variations of the puzzle have been designed with as many as 22 layers, although not mass produced for the public. The current record for a single solve is held by Feliks Zemdegs, who presented a 4.73 second solve at the POPS Open 2016 in December 2016. Feliks Zemdegs also holds the world record for the average of five solves at 6.45 seconds, which he set in July 2016 at the WLS Lato 2016 competition.
Speedcubing is a popular activity among the international Rubik's Cube community, or cubers. Members come together to hold competitions, work to develop new solving methods, and seek to perfect their technique. As a part of the community, puzzle builders and modders try to invent new forms of combination puzzles.
- 1 History
- 2 Solving methods
- 3 Competitions
- 4 World records
- 5 Lubrication
- 6 Building and Modification
- 7 Terminology
- 8 See also
- 9 References
- 10 External links
The Rubik's Cube was invented in 1974 by Hungarian professor of architecture, Ernő Rubik. A widespread international interest in the cube began in 1980, which soon developed into a global craze. On June 5, 1982, the first world championship was held in Budapest, Hungary. 19 people competed in the event and the American Minh Thai won with a single solve time of 22.95 seconds. Other notable attendees include Jessica Fridrich and Lars Petrus, two people who would later be influential in the development of solving methods and the speedcubing community. The height of the Rubik's Cube craze began to fade away after 1983, but with the advent of the Internet, sites relating to speedcubing began to surface. Simultaneously spreading effective speedsolving methods and teaching people new to the cube to solve it for the first time, these sites brought in a new generation of cubers, created a growing international online community, and raised the profile of the art. People prominent in this online community, such as Ron Van Bruchem, Tyson Mao, Chris Hardwick, and Ton Dennenbroek, eventually wanted to meet in person and compete, so twenty years after the first world championship they orchestrated a second one in Toronto in 2003, and another smaller competition in the Netherlands later that same year. This revival of competition sparked a new wave of organized speedcubing events, which include regular national and international competitions. There were twelve competitions in 2004, 58 more from 2005 to 2006, over 100 in 2008, and over 450 in 2014, with more happening every year. There have been seven more World Championships since Budapest's 1982 competition, which are traditionally held every other year, with the most recent in São Paulo, Brazil, in 2015. This new wave of speedcubing competitions have been and still are organised by the World Cube Association (WCA), founded by Ron van Bruchem.
The standard Rubik's Cube can be solved using a number of methods, not all of which are intended for speedcubing. Although some methods employ a layer-by-layer system and algorithms, other significant (though less widely used) methods include corners-first methods, and the Roux method. CFOP, Roux, ZZ, and Petrus are often referred to as the "big four" methods, as they are the most popular and can be used to achieve faster times than the others. The CFOP method is considered the fastest method currently as it is has been used to set the fastest times.
The CFOP (Cross - F2L - OLL - PLL) method, also known as the Fridrich Method, was named after one of its inventors, Jessica Fridrich, who finished second in the 2003 Rubik's Cube World Championships. While it is known as the Fridrich method, its origins are actually credited to David Singmaster, who was one of the first to publish a layer by layer method of solving in 1980, and Guus Razoux Schultz, who built upon this and developed a more efficient system for the first two layers (F2L). Jessica Fridrich then finished developing the method and published it online in 1997, an event that was very influential in the revival of competitive speedcubing. The first step of the method is to solve a cross-shaped arrangement of edge pieces on the first layer. The remainder of the first layer and all of the second layer are then solved together in what are referred to as "corner-edge pairs" or slots. Finally, the last layer is solved in two steps — first, all of the pieces in the layer are oriented to form a solid color (but without the individual pieces always being in their correct places on the cube). This step is referred to as orientation and is usually performed with a single set of algorithms known as OLL (Orientation of Last Layer). Then, all of those pieces are permuted to their correct spots. This is also usually performed as a single set of algorithms known as PLL (Permutation of Last Layer).
The CFOP method can be used as a less-advanced method by dividing the steps into more steps, reducing the number of algorithms you need to learn but sacrifices time. Most people start learning CFOP with 4LLL (Four-look last layer), which is the less advanced, slower, and algorithm-reducing way to learn CFOP. The 4 steps are divided into Edge Orientation, Corner Orientation, Corner Permutation, and Edge Permutation. Later on, you can learn Full PLL which replaces the permutation of the edges and corners, making the solve more efficient and therefore faster. Even later, you can learn Full OLL which will replace the Orientation of the corners and edges, again making the solve faster.
The CFOP method is a widely used speedcubing method. Its popularity stems from the speed at which it can be easily performed. Many advanced speedcubers have also learned additional sets of algorithms for the last layer, such as Corners of Last Layer (COLL), which orients and permutes the corners when the edges are oriented.
The Roux method was invented by French speedcuber Gilles Roux. The first step of the Roux method is to form a 3×2×1 block usually placed in the lower portion of the left layer. The second step is to create another 3×2×1 on the opposite side, such that each block is sharing a bottom color. The remaining four corners are then solved using a set of algorithms known as CMLL (Corners of the Last Layer, without regard to the M-slice), which leaves six edges and four centers that are solved in the last step, L6E or LSE (Last Six Edges).
This method is not as dependent on algorithm memorization as the CFOP method, since all but the third step is done with intuition as opposed to predefined sets of algorithms. The Roux method can be performed without rotations (unlike the CFOP method) which means it is easier to look ahead (solving a collection of pieces while at the same time looking for the solution to the next step) while solving.
The ZZ method, short for Zbigniew Zborowski, is a modern speedcubing method originally proposed by Zbigniew Zborowski in 2006. The method was designed specifically to achieve high turning speed by focusing on move ergonomics, and is the combination of a block-building method and a layer-by-layer method. The initial pre-planned step is called EOLine, and is the most distinctive hallmark of the ZZ method. It involves orienting all edges while placing two oppositely placed down-face edges aligned with the correspondingly colored center. The next step solves the remaining first two layers using only left, right, top and bottom face turns, one of the advantages of ZZ. On completion of the first two layers, the last layer's edges are all correctly oriented because of edge pre-orientation during EOLine. The last layer may be completed using a number of techniques including those used in the CFOP method. An expert variant of this method (ZZ-a) allows the last layer to be completed in a single step with an average of just over 12 moves and knowledge of at least 472 algorithms.
The Petrus method, named after its inventor Lars Petrus, is considered to be more intuitive than the structured CFOP method. The first step of the Petrus method is to solve a 2×2×2 block of the cube. This block is then extended to a solved 2×2×3 block. All edges that are unoriented are then oriented, and then the first and second layers are completed using only turns of the right layer and the upper layer. Next, the top corners are put in the right place and the layer is oriented correctly (all stickers facing up) and finally the last edges are permuted (moved around). Lars Petrus developed this method to address what he felt were inherent inefficiencies in layer-by-layer approaches. This method is often used as the basis of a method for fewest moves competitions.
Corners-first methods involve solving the corners then finishing the edges with slice turns. Corners-first solutions were common in the 1980s, and was one of the most popular methods that 1982 world champion Minh Thai used. Currently corners-first solutions are less common among speedsolvers. Dutch cuber Marc Waterman created a corners-first method in the cube craze, and averaged 18 seconds in the mid-late 1980s.
World Cube Association
Since 2003, speedcubing competitions have been held regularly. The World Cube Association (WCA) was formed in 2004 to govern all official competitions. For a competition to be official, it must be approved by the WCA and follow the WCA regulations. Included in the regulations is the necessity of having one or more WCA delegate in attendance. A delegate's main role is to ensure all regulations are followed during the competition. Once the competition has finished, the results are uploaded on to the WCA website.
The majority of puzzle competitions are held using an average of 5 format. This involves the competitor solving 5 times in the round; the fastest and slowest solve are disregarded and the mean of the remaining 3 is used. The 6×6×6, 7×7×7 and solving-with-the-feet events are ranked by mean of 3. This is the same but only three solves are done, and no solves are disregarded when calculating the mean. 3×3×3 blindfolded and fewest moves challenge are held either by mean of 3 or best of 3. 4×4×4 blindfolded, 5×5×5 blindfolded and multiple blindfolded are held using best of 1, 2 or 3, depending on the competition. Occasionally an event is held using an uncommon format, for example best of 3 for 3×3×3.
When a round begins, competitors hand in the puzzle they will use. Puzzles are scrambled using a computer-generated scramble. Each round, five, three or one (depending on the format, mentioned above) scrambles are used. Every competitor in the round will receive each scramble once. Before starting a solve, a competitor has up to 15 seconds to inspect the puzzle (inspection is removed for blindfolded events). This is monitored by a judge with a stopwatch. Once the solve is complete, the judge records the time on the competitor's scorecard and it is signed by both. If the puzzle is unsolved and the timer is stopped, the time is recorded as "DNF" (did not finish). There are also numerous reasons why the solve can receive a two-second addition to the solve time, such as a face being more than 45 degrees off, or the competitor going over the allowed inspection time. A competitor can also receive an extra solve to replace the one just completed, for example having a timer malfunction or being deliberately distracted by another person.
Currently[when?], the official timer used in competitions is the StackMat timer. This device has touch-sensitive pads that are triggered by the user lifting one or both of their hands to start the time and placing both their hands back on the pads after releasing the puzzle to stop the timer.
Official competitions are currently being held in several categories.
|Speedsolving||2×2×2, 3×3×3, 4×4×4, 5×5×5, 6×6×6, 7×7×7|
|Blindfolded solving||3×3×3, 4×4×4, 5×5×5|
|Solving with feet||3×3×3|
|Solving in fewest moves||3×3×3|
Competitions will often include events for speedsolving these other puzzles, as well:
World Rubik's Cube Championships
The WCA organizes the World Rubik's Cube Championship as the main international competition once every two years. The latest championship was held in São Paulo, Brazil, from July 17–19, 2015. The next championship will be held in Paris, France, in July 2017.
|I||1982||Budapest||June 5||19||1||1||Minh Thai||22.95|||
|II||2003||Toronto||August 23–24||15||9||13||Dan Knights||20.00|||
|III||2005||Lake Buena Vista||November 5–6||16||9||15||Jean Pons||15.10|||
|IV||2007||Budapest||October 5–7||28||10||17||Yu Nakajima||12.46|||
|V||2009||Düsseldorf||October 9–11||32||12||19||Breandan Vallance||10.74|||
|VI||2011||Bangkok||October 14–16||35||12||19||Michał Pleskowicz||8.65|||
|VII||2013||Las Vegas||July 26–28||35||10||17||Feliks Zemdegs||8.18|||
|VIII||2015||São Paulo||July 17–19||37||11||18||Feliks Zemdegs||7.56|||
Note: For averages of 5 solves, the best time and the worst time are dropped, and the mean of the remaining 3 solves is taken. When only 3 solves are done, the mean of all 3 is taken as normal.
|Event||Type||Result (Min:Sec.100ths)||Person||Competition||Result Details (Min:Sec.100ths)|
|2×2×2||Single||00:00.49||Maciej Czapiewski||Grudziądz Open 2016||—|
|Average||00:01.51||Lucas Etter||Music City 2015||00:01.24 / 00:01.69 / 00:02.21 / 00:01.45 / 00:01.39|
|3×3×3||Single||00:04.73||Feliks Zemdegs||POPS Open 2016||—|
|Average||00:06.45||Feliks Zemdegs||WLS Lato 2016||00:07.16 / 00:06.58 / 00:06.79 / 00:05.88 / 00:05.99|
|4×4×4||Single||00:21.54||Feliks Zemdegs||China Championship 2015||—|
|Average||00:26.03||Sebastian Weyer||German Nationals 2014||00:26.06 / 00:27.08 / 00:26.36 / 00:25.68 / 00:24.86|
|5×5×5||Single||00:41.27||Feliks Zemdegs||Melbourne Cube Days 2016||—|
|Average||00:49.32||Feliks Zemdegs||Euro 2016||00:53.08 / 00:48.25 / 00:52.00 / 00:45.52 / 00:47.71|
|6×6×6||Single||01:32.47||Feliks Zemdegs||Sydney Championship 2016||—|
|Average||01:37.85||Feliks Zemdegs||Melbourne Cube Days 2016||01:40.81 / 01:36.66 / 01:36.07|
|7×7×7||Single||02:20.66||Feliks Zemdegs||Euro 2016||—|
|Average||02:22.55||Feliks Zemdegs||Sydney Championship 2016||02:21.91 / 02:21.06 / 02:24.69|
|Megaminx||Single||00:33.17||Yu Da-Hyun||Busan Winter 2016||—|
|Average||00:37.25||Yu Da-Hyun||Busan Winter 2016||00:38.36 / 00:33.17 / 00:38.48 / 00:34.90 / 00:38.74|
|Pyraminx||Single||00:01.32||Drew Brads||Lexington Fall 2015||—|
|Average||00:02.14||Drew Brads||US Nationals 2016||00:02.01 / 00:03.42 / 00:02.32 / 00:01.57 / 00:02.08|
|Square-1||Single||00:06.84||Tommy Szeliga||Indiana 2016||—|
|Average||00:09.07||Brandon Lin||Clifton Winter 2017||00:07.61 / 00:10.24 / 00:10.49 / 00:08.81 / 00:08.17|
|Rubik's Clock||Single||00:03.73||Nathaniel Berg||Danish Open 2015||—|
|Average||00:05.33||Evan Liu||Birmingham Open 2016||00:05.21 / 00:07.10 / 00:05.77 / 00:04.95 / 00:05.02|
|Skewb||Single||00:01.10||Jonatan Kłosko||ŚLS Wodzisław Śląski 2015||—|
|Average||00:02.63||Michał Rzewuski||GLS Cup V 2016||00:02.33 / 00:02.64 / 00:02.53 / 00:03.68 / 00:02.71|
|Łukasz Burliga||Elektryk Cube Race 2016||00:02.34 / 00:04.32 / 00:02.82 / 00:02.21 / 00:02.73|
|3×3×3: Blindfolded||Single||00:18.50||Kaijun Lin||Shanghai Winter is Coming 2016||—|
|Average||00:24.38||Kaijun Lin||Shanghai Winter is Coming 2016||00:25.40 / 00:18.50 / 00:29.24|
|4×4×4: Blindfolded||Single||01:41.90||Kaijun Lin||Big 'n Blind 2016||—|
|5×5×5: Blindfolded||Single||04:42.06||Roman Strakhov||Finnish Championship 2016||—|
|3×3×3: Multiple Blindfolded||Single||41/41||Marcin Kowalczyk||SLS Swierklany 2013||54:14|
|3×3×3: One-handed||Single||00:06.88||Feliks Zemdegs||Canberra Autumn 2015||—|
|Average||00:10.59||Max Park||2FTI San Diego 2016||00:11.43 / 00:10.20 / 00:11.49 / 00:09.42 / 00:10.15|
|3×3×3: With feet||Single||00:20.57||Jakub Kipa||Radomsko Cube Theory 2015||—|
|Average||00:28.16||Jakub Kipa||Mielec Cube Day 2016||00:32.86 / 00:21.83 / 00:29.79|
|3×3×3: Fewest moves||Single||19||Tim Wong||Irvine Fall 2015||—|
|Marcel Peters||Cubelonia 2016||—|
|Vladislav Ushakov||PSU Open 2016||—|
|Average||24.33||Marcel Peters||Schwandorf Open 2016||24 / 25 / 24|
Members of the cubing community lubricate their cubes to allow them to be manipulated faster, easier, and more reliably than a non-lubricated cube. The WCA allows lubrication for official competitions.
Popular lubricants among speedcubers are:
- Lubicle Silk
- Lubix Cube Lubricant
- Maru Lubricant
- Traxxas 30/50K Differential Oil
- Cubesmith Lubricant
- Cubicle Silicone Lube/Lubicle
- SpeedCubeShop Speed Lube
Checking a lubricant's MSDS is often helpful in identifying cube-damaging ingredients.
Building and Modification
A smaller portion of the cubing community, known as modders, dedicate themselves to creating ideas for new cubes, modifying existing cubes, and designing and producing the new puzzles themselves.
The modding community, larger than the aforementioned, takes existing puzzles and executes a process to have some desired effect. Most mods consist of simply sanding pieces down, to reduce friction, while other, more complex ones, involve cutting, shaping, and adding plastic to the puzzle to change shape and its overall mechanism and difficulty. These kinds of mods can range from simple ones such as the Cutter Cube, in which the center layer is misaligned, and the pieces are shaved down to make it seem as though it isn't, to more complex ones such as the Ghost Cube. It can be of any type.
Below are some definitions of words generally used by the speedcubing community. For a more complete list of speedcubing terminology, see the cubefreak.net glossary.
- A predefined sequence of moves used to effect a specific change on the cube. Often referred to as alg or (less commonly) an algo.
- Blindfolded solving, i.e. memorize, don blindfold, then solve.
- Short for Bad Job, usually used to harass or tease a cuber on a bad solve.
- Center piece
- One of the centers of the faces of the cube. The centers never move relative to each other on an NxNxN cube, where N is odd. On NxNxN cubes where N>3, every piece with only one sticker is referred to as a 'center piece', including those pieces that can move relative to each other.
- Corners of the Last Layer. This is the first of two steps of one of the methods of solving the last layer of the cube. In the process, edges may be unoriented. This is used in Corners First methods for the last layer, in which the first all corners are solved, followed by the edges (see ELL). CLL is also commonly used to solve the last layer of a 2x2x2 cube in one step.
- A commutator is a sequence of the form X.Y.X'.Y' (also represented as [X:Y] or [X,Y]) which affects only specific portions of the cube, leaving the rest untouched. This is used in Blindfolded solving and Fewest Moves Competition.
- Corner piece
- One of the 8 pieces with exactly three stickers, called a "corner" piece because a corner is exposed.
- Someone who solves a Rubik's cube, any of its other sizes, and/or other shaped puzzles.
- One of the mechanically independent pieces that make up a puzzle. The cubies do not include fixed center pieces, the central axis to which they are attached, or any other internal pieces (Such as the internal edges of a 4x4 or 2x2).
- To rotate pieces' positions on the cube. e.g. a 3-cycle would make cubie set A-B-C become C-A-B.
- Initialism for Did Not Finish, used in competitions and self-timing. e.g. when a piece pop occurs and the competitor decides not to continue solving the puzzle, or when the solver stops the timer with the cube still unsolved.
- Did Not Start, used in competition when the competitor does not begin a solve, either by opting to skip it (common in Blindfold Cubing), by not showing up when he or she is called, or not qualifying for the remaining (usually three) solves of a certain round.
- Edge piece
- One of the 12 pieces with exactly two stickers, called an "edge" piece because only one edge is exposed.
- Edges of the Last Layer. The second of two steps of one of the methods of solving the last layer of the cube, solving the edge pieces without disturbing the corner pieces (see CLL).
- First two blocks. This is used in the Roux method.
- First two layers. This is used in the CFOP (Fridrich), Petrus, and ZZ methods.
- Short for Good Job, usually used to congratulate a cuber on a fast solve
- One section of a cube consisting of a number of cubies that turn as a unit. (e.g. A standard Rubik's Cube has 3 layers.)
- Last Layer. Usually refers to the top layer of the cube, but for the Roux method can refer to the middle layer between the left and right faces.
- A combination of steps that can be used to solve a cube.
- A turn of one of the sides of a puzzle, or knobs in the case of the clock.
- N-look, also known as X-Look
- Refers to the number of algorithms needed to complete a step in a particular solving method, often the last layer, e.g. '4-look LL'.
- Short for One-Handed, it is the event or practice of solving a cube with one hand, left or right.
- Orientation of the Last Layer, usually used in reference to the respective step of the CFOP and ZZ methods.
- Orientation of the Last Layer with Corner Permutation. An advanced technique where multiple algorithms are learned for one OLL case, in order to use one that will solve the case while also permuting the corners, which results in an easy PLL case.
- To change the orientation of a piece.
- Personal Best - personal record time to solve a puzzle. This can either be a single attempt or a trimmed average, depending on context.
- To relocate certain pieces in a way to achieve a desired result.
- Used in various methods, it is a technique that allows the shrinking of algorithm sets by using alternative moves. e.g. Using phasing with ZZ-a will turn it into a reduced subset known as ZZ-b.
- Permutation of the Last Layer. Usually used in reference to the respective step of the CFOP and ZZ methods, in which case it would follow the OLL step.
- Edge Permutation of Last Layer, specifically refers to the PLL cases in which only edges must be permuted to solve the cube.
- When, during a solve, one or more cubies come out of contact with the puzzle, usually causing the puzzle to be unstable, in which, upon turning, more pieces may become loose and possibly pop out too.
- A counter-clockwise move popularly denoted with a ', e.g. 'R Prime', denoted as R', R-, , or Ri. Also (less commonly) known as "inverse" or "inverted".
- The four center pieces and four edge pieces between two opposite layers of the cube. On a cube with four or more layers, it refers to any of the layers of the puzzle that don't have corner pieces.
- Two-Second Penalty, also known as +2
- A penalty of 2 seconds which is added to a solving time in official competitions when the cube is placed back on the timing pad with one or more faces misaligned 45 degrees or more. It can also be given in other cases, such as when the competitor starts the timer too slow or does not correctly stop the timer after finishing the solve.
- Unofficial World Record.
- World Cube Association, the international governing body for official cube competitions.
- Winter Variation, also known as WV
- A subset of algorithms for F2L that allows the user to force all upper-face corners to be oriented correctly, or an OLL-Skip, while the last F2L pair is already formed. It is used when the last F2L pair (One corner and its corresponding edge correctly positioned relative to each other) to be inserted is in the top layer, with the 3 top-layer edges oriented correctly. There are a total of 27 cases. WV has an average lower move-count than the standard OLL.
- Summer Variation
- A subset of algorithms for F2L that allows the user to force all upper-face corners to be oriented correctly, or an OLL-Skip, while the last F2L pair can be solved with R U R' or L' U' L.
- World Record. Can also be "World Rank" when referring to the rank of a person's record in a database.
- Completing an F2L pair during the cross setup, used almost exclusively in the CFOP method.
- Considered one of the holy grails of speedcubing. It is a set of 177 algorithms (Not including mirrors and inverses) with 494 cases to recognize in order to solve the last layer in one look while all of the top edges are oriented with an average move count of ~12.08. Can be used in any layer-by-layer method that ends in N-Look LL, but will only really be efficient in ZZ and Petrus, as these methods keep edges oriented, whereas methods such as CFOP do not keep the edges oriented, becoming a sometimes 2LLL solve.
- A set of 3915 algorithms to solve every possible state that the last layer could be in after completing F2L. The average move count is 12.58.
- YouTube Unofficial Word Record, the fastest of something that is posted on YouTube.
- "WCA Regulations". World Cube Association. Retrieved 2 August 2016.
- "22x22 rubik's cube World Record". YouTube. Retrieved 2 August 2016.
- "World Records for 3x3 single and average". World Cube Association. Retrieved 2 August 2016.
- "Competitions". World Cube Association. Retrieved 2 August 2016.
- "David Singmaster Solution". Van Ness Web. Retrieved 2 August 2016.
- "Guus Razoux Schultz". Speedsolving.com Wiki. Retrieved 2 August 2016.
- "Speed Cubing". Rubik's Official Website. Retrieved 2 August 2016.
- "Rubik's Cube: Algorithms for the last layer". Université Paris 8. Retrieved 2 August 2016.
- Lars Petrus. "Solving Rubik's Cube for speed". Retrieved 13 Jan 2017.
- "World Championship 2017 in Paris, France on July 13-16, 2017". World Cube Association. Retrieved 22 December 2016.
- "World Rubik's Cube Championship 1982". World Cube Association. Retrieved 2 August 2016.
- "World Rubik's Games Championship 2003". World Cube Association. Retrieved 2 August 2016.
- "World Rubik's Cube Championship 2007". World Cube Association. Retrieved 2 August 2016.
- "World Rubik's Cube Championship 2009". World Cube Association. Retrieved 2 August 2016.
- "World Rubik's Cube Championship 2011". World Cube Association. Retrieved 2 August 2016.
- "World Rubik's Cube Championship 2013". World Cube Association. Retrieved 2 August 2016.
- "World Rubik's Cube Championship 2015". World Cube Association. Retrieved 2 August 2016.
- "Records". World Cube Association. Retrieved 2 August 2016.
- "Speedcubing - an overview". Singapore champion guide on How to solve a Rubik's Cube. Retrieved 2 August 2016.
- "WCA Regulations and Guidelines" (PDF). World Cube Association. Retrieved 2 August 2016.