Klotski (from ) is a sliding block puzzle thought to have originated in the early 20th century. The name may refer to a specific layout of ten blocks, or in a more global sense to refer to a whole group of similar sliding-block puzzles where the aim is to move a specific block to some predefined location.
Rules
Like other sliding-block puzzles, several different-sized block pieces are placed inside a box, which is normally 4×5 in size. Among the blocks, there is a special one (usually the largest) which must be moved to a special area designated by the game board. The player is not allowed to remove blocks, and may only slide blocks horizontally and vertically. Common goals are to solve the puzzle with a minimum number of moves or in a minimum amount of time.
Naming
The earliest known reference of the name Klotski originates from the computer version for Windows 3.x by ZH Computing in 1991, which was also included in Microsoft Windows Entertainment Pack. The sliding puzzle had already been trademarked and sold under different names for decades, including Psychoteaze Square Root, Intreeg, and Ego Buster. There was no known widely used name for the category of sliding puzzles described before Klotski appeared.
History
It is still unknown which version of the puzzle is the original. There are many confusing and conflicting claims, and several countries claim to be the ultimate origin of this game. One game—lacking the 5 × 4 design of Pennant, Klotski, and Chinese models but a likely inspiration—is the 19th century 15-puzzle, where fifteen wooden squares had to be rearranged. It is suggested that unless a 19th-century Asian evidence is found, the most reasonably likely path of transmission is from the late 19th century square designs to the early 20th century rectangular, such as Pennant, thence to Klotski and Huarong Road.
United States
The 15-puzzle enjoyed immense popularity in western countries during the late 19th century. Around this time, patents appeared for puzzles using differently shaped blocks. Henry Walton filed in 1893 for a sliding puzzle of identically shaped rectangles. Frank E. Moss filed in 1900 for a sliding puzzle of six squares and four rectangles, which is one of the first known occurrences of sliding puzzle with non-equal blocks. However, the early cognate of Klotski closest in design dates to 1909 in Chicago.
Lewis W. Hardy obtained copyright for a game named Pennant Puzzle in 1909, manufactured by OK Novelty Co., Chicago. The aim of this puzzle is identical to Klotski, and only its default blocks and arrangement are different. Hardy also filed in 1907, which is about a sliding-block puzzle similar to Pennant Puzzle, but with a slightly different combination of blocks and a different goal—not only must the largest block be moved to a specific location, but all of the other blocks must achieve a specific configuration as well. The patent was granted in 1912.
England
John Harold Fleming obtained patent for a puzzle in 1934 in England, with almost identical configuration as described in this page. The puzzle concerned has the same blocks and almost identical placement as forget-me-not, only that the unique horizontal 2×1 block is placed at the bottom instead of beneath the 2×2 block. The patent included a 79-step solution.
China
The Klotski puzzle—with its two-by-two and one-by-two cells and with the same 4 × 5 dimensions—also closely resembles the Chinese game known as (), also known as Pass or Road. Popular versions of used cells with names or images of Han dynasty heroes and villains, based on a famous battle from the Yuan dynasty novel Romance of the Three Kingdoms. The Chinese design, commonly using Chinese names for the heroes, villains, and soldiers, has clear inspiration from the Chinese version of chess, which problematizes the origins of the genre of sliding puzzles.
The first account of occurrence of Klotski in China is in Shaanxi Province, where Lin Dekuan from the Northwestern Polytechnical University noted that children in a village, a countryside in Chenggu county, were playing a version of Klotski made with pieces of paper in 1938.
In 1943, the was publicized by Liang Qing, a teacher in the New Fourth Route Army who learnt it from people living in northern Jiangsu province, among soldiers to enhance their cultural life.