Sokoban [a] is a puzzle video game series in which the player pushes boxes in a warehouse to get them onto storage locations. The game is viewed from a top-down perspective. Boxes can only be pushed, never pulled, and only one box can be pushed at a time. The principal challenge is planning moves correctly to avoid deadlocks, i.e., situations where a box or the player becomes permanently trapped, making the puzzle unsolvable.
Hiroyuki Imabayashi created the first Sokoban game as a hobby in 1981; his company, Thinking Rabbit, commercially released the first enhanced version in December 1982. This initial title became a bestseller in Japan. Between 1982 and 2000, Thinking Rabbit and its licensed partners developed new titles for various platforms. The series made its international debut in 1988 with the U.S. release Soko-Ban. In 2001, Falcon acquired the Sokoban rights and the Thinking Rabbit brand, becoming the series' main developer and licensor; since then, new titles have been published either by Falcon under the Thinking Rabbit brand or by licensed partners.
Over its history, the series has sold over 4.1 million copies worldwide, with more than 40 official games released across various platforms. Reviewers have consistently praised the game's simplicity, its addictive and challenging nature, and the level of thought required. However, it has been criticized for a lack of variety.
Due to the creation of numerous clones, the name "Sokoban," a registered trademark, has become genericized to describe the genre. The series has inspired thousands of custom puzzles, as well as Sokoban-like games. Its core concept of pushing objects to targets has been widely used in puzzles within other video games. Moreover, Sokoban puzzles have been studied in the fields of computational complexity and artificial intelligence.
Sokoban takes place in a warehouse viewed from above and composed of walls and floor squares. A floor square may be empty, occupied by the player, or occupied by a box. Some floor squares are storage locations. The number of storage locations equals the number of boxes. The objective of the puzzle is to push all boxes onto storage locations. [1]
The player can move one square at a time, either horizontally or vertically, onto an empty floor square. [2] Boxes and walls block the player's movement, but the player can walk up to a box and push it to an empty square directly beyond it. If a box is pushed against a wall or another box, it does not move. Pulling boxes is not possible. [3]
Sokoban requires players to plan several moves ahead and consider all possible outcomes. [4] Careful decision-making is essential to avoid pushing a box into a position where it becomes permanently trapped against a wall, another box, [2] or in a dead end; [5] or pushing boxes that permanently trap the player and prevent access to the remaining boxes. [6] : 38 Such situations create deadlocks that make the puzzle unsolvable, regardless of future moves. [7]
In 1981, Hiroyuki Imabayashi created the first Sokoban game for the NEC PC-8001 as a hobby, featuring text-based graphics and five original levels. The core mechanic was inspired by Hudson Soft's 1980 game Aldebaran #1 for the MZ-80K, [8] where players pushed luggage to block radiation. [9] Imabayashi envisioned a warehouse setting where incorrect box placement could make further progress difficult or even impossible, and designed levels that proved challenging even for his friends. At the time, his wife's parents owned a record store with a small computer section. A salesman who saw the game suggested it had commercial potential. [10] Imabayashi later ported the game to the NEC PC-8801, enhancing the graphics and expanding it to twenty levels. In 1982, he founded Thinking Rabbit in Takarazuka, Japan, and released the NEC PC-8801 version as the first commercial Sokoban game in December. [11] [12]
In 1983, the Japanese magazine PC Magazine published Sokoban Extra Edition as a type-in program with ten new puzzles, developed by Thinking Rabbit on request. [13] In 1984, Thinking Rabbit released Sokoban 2, which included a puzzle editor. [14] Throughout the 1980s, new titles appeared on various Japanese platforms, including home computers such as the MSX and PC-9801, and consoles like the Famicom, Sega SG-1000, Sega Mega Drive, and Game Boy. [15] These releases were either developed by Thinking Rabbit or licensed to other companies. [11] In 1987, Spectrum HoloByte in California licensed Sokoban from Japan's ASCII, adapted the MSX version for IBM PC, Apple II, and Commodore 64, added features for the U.S. market, and released it as Soko-Ban in early 1988. [16] [17] The official series continued in Japan during the 1990s with new titles for the Super Famicom, Windows, Macintosh, and PlayStation. [18]
Around 2000, Thinking Rabbit became inactive but remained a legal entity. [9] In 2001, the Japanese software company Falcon acquired the copyrights and trademarks for Sokoban and Thinking Rabbit, [19] becoming the official developer and licensor. From 2004 to 2007, Falcon developed several titles for Japanese mobile phones. [20] [21] Between 2015 and 2018, Falcon developed five Sokoban titles for Windows and the smartphone game Sokoban Touch (2016), all of which were published by Falcon under the Thinking Rabbit brand. [18] In 2018, Falcon developed three Sokoban titles for Japanese digital terrestrial television broadcasters. [18]
Since its debut in 1982, more than 40 official Sokoban games have been released on various platforms, primarily in Japan but also internationally. Most titles are standalone, with a few sequels. The core mechanic of pushing boxes to storage locations has remained consistent in nearly all official titles, with the following exceptions:
The following table lists the titles in the Sokoban series. [18] [15]
| Title | Release | Platform | Developer | Publisher | Region |
|---|---|---|---|---|---|
| Sokoban (倉庫番) | 1982-1983 | NEC PC-8801 NEC PC-6001mkII NEC PC-8001mkII Fujitsu FM-7 Sharp MZ-2000 Sharp X1 | Thinking Rabbit | Thinking Rabbit | Japan |
| Sokoban Extra Edition (倉庫番[番外編]) | 1983 | NEC PC-8801 | Thinking Rabbit | PC Magazine | Japan |
| Sokoban 2 (倉庫番2) | 1984 | NEC PC-9801 NEC PC-8801 NEC PC-6001mkII NEC PC-8001mkII Fujitsu FM-7 Sharp X1 MB-S1 | Thinking Rabbit | Thinking Rabbit | Japan |
| Sokoban ROM Pack (倉庫番 ROM Pack) | 1984 | MSX | ASCII | ASCII | Japan |
| Sokoban Tape Pack (倉庫番 Tape Pack) | 1984 | MSX | |||
| Sokoban (倉庫番) | 1985 | Game Pocket Computer | Epoch | Epoch | Japan |
| Sokoban (倉庫番) | 1985 | SG-1000 | Sega | Sega | Japan |
| Sokoban Special of Tears (涙の倉庫番スペシャル) | 1986 | Famicom Disk System | ASCII | ASCII | Japan |
| Soko-Ban | 1988 | IBM PC Commodore 64 Apple II | Spectrum HoloByte [16] | Spectrum HoloByte | North America |
| Sokoban Perfect (倉庫番Perfect) | 1989 | NEC PC-9801 Sharp X68000 FM Towns | Thinking Rabbit | Thinking Rabbit | Japan |
| MSX2 | Micro Cabin | Micro Cabin | |||
| Sokoban (倉庫番) BoxxleNA | 1989 | Game Boy | Pony Canyon | Pony CanyonJP FCI NA | Japan, North America |
| 1991NA | |||||
| Sokoban 2 (倉庫番2) Boxxle IINA | 1990 | Game Boy | |||
| 1992NA | |||||
| Sokoban Deluxe (倉庫番Deluxe) | 1990 | Namco System 1 | Namco | Namco | Japan |
| The Greatest Sokoban in History (史上最大の倉庫番) Shove It! The Warehouse GameNA | 1990 | Sega Genesis | NCS [26] | Masaya JP DreamWorksNA | Japan, North America |
| Sokoban (倉庫番) | 1990 | Game Gear | Riverhill Soft | Riverhill Soft | Japan |
| Sokoban World (倉庫番World) BoxyboyNA | 1990 1991 | TurboGrafx-16 | Media Rings | Media RingsJP NEC NA | Japan, North America |
| Sokoban Revenge (倉庫番Revenge) | 1991 | NEC PC-9801 | Thinking Rabbit | Thinking Rabbit | Japan |
| Super Sokoban (Super倉庫番) | 1993 | Super Famicom | Pack-In-Video | Pack-In-Video | Japan |
| Sokoban for Windows (倉庫番 for Windows) | 1995 | Windows | Itochu | Itochu | Japan |
| Sokoban for Macintosh (倉庫番 for Macintosh) | 1996 | Macintosh | |||
| Ultimate Sokoban (究極の倉庫番) | 1996 | PlayStation | |||
| Sokoban Basic (倉庫番ベーシック) | 1997 | PlayStation | |||
| Sokoban Selection (倉庫番セレクション) | 1997 | Windows Macintosh | |||
| Sokoban Special 102 (倉庫番スペシャル102) | 1998 | Windows | Itochu | Fujitsu Parex | Japan |
| Ultimate Sokoban (究極の倉庫番) | 1998 | Windows | Itochu | Itochu | Japan |
| Sokoban Basic 2 (倉庫番ベーシック2) | 1998 | PlayStation | |||
| Sokoban Basic (倉庫番ベーシック) | 1998 | Windows | Unbalance | Unbalance | Japan |
| Power Sokoban (Power倉庫番) | 1999 | Super Famicom | Nintendo | Nintendo | Japan |
| Sokoban Legend: Land of Light and Darkness (倉庫番伝説 光と闇の国) | 1999 | Game Boy | J Wing | J Wing | Japan |
| Sokoban: Guide to Difficult Puzzles (倉庫番 難問指南) | 1999 | PlayStation | Unbalance | Unbalance | Japan |
| 2000 | Windows | ||||
| Sokoban (倉庫番) | 2000 | Windows | |||
| Sokoban First Step (倉庫番ファーストステップ) | 2004 | EZweb | Falcon [20] | Square Enix | Japan |
| Sokoban Perfect (倉庫番パーフェクト) (1/2/3) | 2004 | EZweb | |||
| Sokoban First Step (倉庫番ファーストステップ) | 2004 | i-mode | Falcon [21] | Dwango | Japan |
| Sokoban Perfect (倉庫番パーフェクト) (1-1/1-2/1-3/2-1/2-2/2-3/3-1/3-2/3-3) | 2004-2005 | i-mode | |||
| Konami Wai Wai Sokoban (コナミワイワイ倉庫番) | 2007 | i-mode | Konami [27] | Konami | Japan |
| Sokoban Perfect Plus A-side (倉庫番パーフェクト プラス A面) | 2015 | Windows | Falcon | Thinking Rabbit | Japan |
| Sokoban Perfect Plus B-side (倉庫番パーフェクト プラス B面) | 2015 | Windows | |||
| Sokoban First Step Plus (倉庫番ファーストステップ プラス) | 2016 | Windows | |||
| Sokoban Revenge Reprint (倉庫番リベンジ 復刻版) | 2016 | Windows | |||
| Sokoban Touch | 2016 | Android iOS | Worldwide | ||
| Sokoban Smart (倉庫番スマート) | 2018 | Windows | Japan | ||
| Chukyo-kun no Sokoban (チュウキョ~くんの倉庫番) | 2018 | Digital terrestrial television | Falcon | Chukyo Television | Japan |
| Dayon no Sokoban (だよんの倉庫番) | 2018 | Digital terrestrial television | Miyagi Television | ||
| Kumojiro no Sokoban (くもジローの倉庫番) | 2018 | Digital terrestrial television | Nippon Television | ||
| Minna no Sokoban (みんなの倉庫番)JP The Sokoban | 2019JP | Nintendo Switch PlayStation 4 | Unbalance | Unbalance | Japan |
| 2021 | Worldwide |
The first Sokoban title became a bestseller in Japan, with over 25,000 copies sold by July 1984. [28] [29] [30] Early releases for Japanese home computers, such as the NEC PC-9801 and Sharp X1, sold more than 100,000 copies combined. [31] The MSX version, published by ASCII, sold over 400,000 copies and was considered a commercial success. [16] [32] The U.S. release, Soko-Ban, sold over 50,000 copies by mid-September 1988. [16] By 2018, Chukyo Television Broadcasting reported that the series had sold over 4.1 million copies worldwide since its 1982 debut. [33]
In 1990, Famicom Winning Guide recognized Sokoban as a staple puzzle game, noted for its difficulty, depth, and continued presence across multiple platforms. [34] Reviewers often emphasized the game's addictive nature. Micomgames staff remarked that players would find it difficult to stop playing the first Sokoban. [4] In 1988, Roy Wagner of Computer Gaming World suggested that anyone trying the US version, Soko-Ban, would likely remain absorbed for an extended period. [35] The Computer Entertainer newsletter described the game as fascinating and almost impossible to stop playing. [36] In its console reviews, Computer and Video Games magazine called Sokoban for Game Boy "an infuriatingly addictive little title" and compared its appeal to Tetris . [37]
Commentators often highlighted one of three aspects of the game: its simplicity, the level of thought it required of players, or its challenging nature. Micomgames staff, however, emphasized both simplicity and the thinking required of players, describing the first Sokoban as simple yet requiring deep thought comparable to playing Go or Shogi. [4] Family Computer magazine's All Catalog supplement described Sokoban for Game Boy as great due to the simplicity of its gameplay, [38] and Computer and Video Games magazine staff described it as one of the Game Boy's "simple but effective puzzle games." [37] Reviewers for the German magazine Happy Computer praised Soko-Ban as a brilliant logic puzzle that kept players thinking without pressure and recommended that players carefully observe a level before moving a box, [39] and in Computer Gaming World, Wagner summarized it as "very playable and mentally challenging." [35] In Game Player's magazine, Tom R. Halfhill reviewed Shove It! for the Sega Genesis, noting it was challenging and would require players to plan their moves carefully, [40] and reviewing Boxxle for Game Boy, he stated that it required careful planning or plenty of trial and error (usually both). [41] He later commented on Boxyboy for the TurboGrafx-16 that while the initial rooms were not difficult, players would eventually encounter one that "seems impossible." [42]
The series faced criticism for its lack of variety. Tom R. Halfhill observed that all puzzles in Shove It! were essentially the same. [40] He also noted that Boxxle's gameplay could become repetitive, with only the number and arrangement of crates and the room shape varying. [41] In his review of Boxyboy, he found it "virtually identical" to Shove It! and Boxxle, concluding that these games required players to enjoy solving the same type of puzzle repeatedly. [42]
Numerous clones have been created, [43] and the term "Sokoban," a registered trademark, has become genericized to describe the genre. [44] Thousands of custom Sokoban puzzles, spanning various difficulty levels, are freely available online, [45] [46] along with software tools such as solvers [47] and solution optimizers. [44] The Sokoban puzzle principle, which involves pushing objects to the correct targets, is widely used in gaming. [48] Despite advances in computer and console power during the 1980s and 1990s, many games continued to use tile- and grid-based movement, making object-pushing puzzles common. [49] As a result, many older games featured puzzles similar to Sokoban. [49] Titles such as Adventures of Lolo (1989), LIT (2009), and The Legend of Zelda series incorporated this principle in their gameplay. [48] [49] Resident Evil 2 (1998) also used this mechanic in a puzzle, requiring players to move statues to marked areas with attention to their orientation. [49] Additionally, Sokoban-like games such as Sokomania 2 (2014) introduced new mechanics, including switches and conveyor belts. [48]
The computational problem of solving Sokoban puzzles has been studied using computational complexity theory, and is known to be NP-hard [50] [51] and PSPACE-complete. [52] [53] Solving non-trivial Sokoban puzzles is difficult for computers because of the high branching factor (many legal pushes at each turn) and the considerable search depth (many pushes needed to reach a solution). [54] [55] Even small puzzles can require lengthy solutions. [56]
Sokoban puzzles provide a challenging testbed for developing and evaluating automated planning techniques. [57] The first documented automated solver, Rolling Stone, was developed at the University of Alberta. It employed a conventional search algorithm enhanced with domain-specific techniques such as deadlock detection. [6] [58] A later solver, Festival, introduced the FESS search algorithm and became the first automatic system to solve all ninety puzzles in the widely used XSokoban test suite. [59] [60] Despite these advances, even the most sophisticated solvers cannot solve many complex puzzles that humans can solve with time and effort, using their ability to plan, recognize patterns, and reason about long-term consequences. [61] [62] [63]