Sokoban

Sokoban
Sokoban official fan kit banner
Genre(s)Puzzle
Developer(s)Thinking Rabbit
ASCII
Unbalance
Publisher(s)Thinking Rabbit
ASCII
Unbalance
Creator(s)Hiroyuki Imabayashi
Platform(s)
  • Various
First releaseSokoban
1982
Latest releaseThe Sokoban
2021

Sokoban[a] is a series of puzzle video games in which the player pushes boxes around in a warehouse, trying to get them to storage locations. Hiroyuki Imabayashi created the first Sokoban game in 1981 as a personal project. It was the basis for the first commercial release, published in Japan in 1982 by his company Thinking Rabbit for the NEC PC-8801 computer. It was ported to various platforms, and new titles followed over the years. Sokoban became popular in Japan and internationally, and the series has remained active, with new titles released as recently as 2021. Sokoban has inspired unofficial versions, thousands of custom puzzles, similar games, and artificial intelligence research.

Gameplay

A Sokoban puzzle being solved

The warehouse is a grid composed of floor squares and impassable wall squares. Some floor squares contain a box and some are marked as storage locations. The number of boxes equals the number of storage locations.

The player, often represented as a worker character, can move one square at a time horizontally or vertically onto empty floor squares, but cannot pass through walls or boxes.

To move a box, the player walks up to it and pushes it to an empty square directly beyond the box. Boxes cannot be pushed to squares with walls or other boxes, and they cannot be pulled.

The puzzle is solved when all boxes are on storage locations.

Progressing through the game requires careful planning and precise maneuvering.[2] A single mistake, such as pushing a box into a corner or obstructing the path of others, can render the puzzle unsolvable, forcing the player to backtrack or restart. Anticipating the consequences of each push and considering the overall layout of the puzzle are crucial to avoid deadlocks and complete the puzzle successfully. A deadlock is a situation from which the puzzle cannot be solved, regardless of subsequent moves.[3]

Deadlocks

Common deadlocks are:[4]

  1. Two boxes placed together along a wall.
  2. A box in a corridor alongside a wall, which can still be pushed, but permanently lacks access to any storage location.
  3. A box in a corner.
  4. A box in a dead end.
  5. Four boxes in a square formation.
  6. Three boxes forming an L-shape in a wall corner.

History

In 1981,[5] Hiroyuki Imabayashi created the first Sokoban game as a personal project for the NEC PC-8001 computer.[6][7][8] He used it as the basis for the first commercial game, also titled Sokoban, published for the NEC PC-8801 computer in December 1982 by his company, Thinking Rabbit, based in Takarazuka, Japan. In subsequent years, ports and new titles for various platforms appeared. In 1988, Spectrum HoloByte published Sokoban in the U.S. for the IBM PC, Commodore 64, and Apple II as Soko-Ban.[9] In 1990, FCI released Boxxle for the Game Boy in both North America and Europe,[10] followed by Boxxle II in 1992.[11] Between 1996 and 2000, several Sokoban games were released for Windows and PlayStation in Japan.[12] In 2001, the Japanese software company Falcon acquired the copyright to the official Sokoban games and the trademarks for Sokoban and Thinking Rabbit.[13] Since then, Falcon has continued to develop and license official Sokoban games.

Versions

Since its debut in 1982, Sokoban has been released on various platforms, primarily in Japan but also in other regions. Most titles are independent without a continuous narrative, though a few are direct sequels to a specific earlier release—for example, Sokoban 2 (1984) follows Sokoban (1982), and Sokoban Revenge (1991) is a sequel to Sokoban Perfect (1989). The following tables list a selection of official Sokoban titles.[14]

Japan releases

Year Title Platform Developer Publisher
1982 Sokoban (倉庫番)[15][16] NEC PC-8801 Thinking Rabbit Thinking Rabbit
1983 Sokoban Extra Edition (倉庫番[番外編])[17] PC Magazine
1984 Sokoban 2 (倉庫番2)[18] Thinking Rabbit
1986 Namida no Sokoban Special (涙の倉庫番スペシャル) Famicom Disk System ASCII ASCII
1989 Sokoban Perfect (倉庫番Perfect) NEC PC-9801 Thinking Rabbit Thinking Rabbit
1991 Sokoban Revenge (倉庫番Revenge) Thinking Rabbit
2018 Sokoban Smart (倉庫番スマート) Windows Falcon Thinking Rabbit

US releases

Year Title Platform Developer Publisher
1988 Soko-Ban[19] IBM PC ASCII Spectrum HoloByte
1990 Boxxle Game Boy Atelier Double FCI
1990 Shove It! The Warehouse Game Sega Genesis NCS DreamWorks
1990 Boxyboy TurboGrafx-16 Thinking Rabbit NEC
1992 Boxxle II Game Boy Atelier Double FCI

Worldwide releases

Year Title Platform Developer Publisher
2016 Sokoban Touch Android, iOS Falcon Thinking Rabbit
2021 The Sokoban Nintendo Switch, PlayStation 4 Unbalance Unbalance

Reception

By June 1984, the first commercial release of Sokoban had sold 22,000 copies in Japan;[20] by March 1985, it had reached 30,000 copies.[21]

Sokoban was a hit in Japan. According to Spectrum Holobyte, the game had sold over 400,000 copies there before the 1988 release of the title Soko-Ban in the United States.[22][23] That title received a positive review from Computer Gaming World, which described the game as simple yet mentally challenging and praised its addictive nature.[24]

Legacy

Name genericization

The name Sokoban is a registered trademark for video game titles. However, the core mechanics—pushing boxes to storage locations on a grid—is not protected by copyright or patent. This has allowed the widespread creation of numerous unofficial versions.[25] Some feature only custom levels, while others include level designs that may be subject to copyright. As a result, the term Sokoban has become informally genericized and is commonly used to refer to any game with these mechanics, regardless of origin.[26] Standalone levels are frequently described as Sokoban puzzles.

Cultural impact

An active fan community has produced thousands of custom puzzles,[27] and software tools, including puzzle editors, solvers,[28] and solution optimizers.[29]

Derivatives

Sokoban is considered the originator of a puzzle game subgenre featuring box-pushing mechanics, commonly referred to as "Sokoban-like" games.[30][31]

Alternative tilings

While Sokoban is played on a square grid, its fundamental rules are, in principle, applicable to boards with other tilings. Hexoban[32] exemplifies this, utilizing regular hexagons.

Multiple pushers

In the variant Multiban,[33] the puzzle contains more than one pusher. In the game Sokoboxes Duo,[34] strictly two pushers collaborate to solve the puzzle.

Designated storage locations

In Sokomind Plus,[35] some boxes and target squares are uniquely numbered. In Block-o-Mania,[36] the boxes have different colours, and the goal is to push them onto squares with matching colours.

Alternative game objectives

Several variants feature different objectives from the traditional Sokoban gameplay. For instance, in Interlock[37] and Sokolor,[38] the boxes have different colours, and the objective is to move them so that similarly coloured boxes are adjacent. In CyberBox,[39] each puzzle has a designated exit square, and the objective is to reach the exit by pushing boxes, potentially more than one simultaneously. In Picoban,[40] the objective is to reach a green stone, although access may be blocked by one or more doors that are unlocked by different mechanisms, such as obtaining a key or placing a box on every storage location. In a variant called Beanstalk,[41] the objective is to push the elements of the puzzle onto a target square in a fixed sequence.

Additional game elements

Push Crate, Sokonex,[42] Xsok, CyberBox,[43] Block-o-Mania,[44] and Picoban[40] all add new elements to the basic puzzle. Examples include holes, teleports, moving blocks, one-way passages, doors, lasers, and mirrors.

Character actions

In Pukoban,[45] the character can pull boxes in addition to pushing them.

Unofficial game modes

There are a few unofficial game modes for Sokoban:

Reverse mode
Some Sokoban programs allow players to play a puzzle backward. Starting with all boxes on storage locations, the player pulls the boxes to return to the initial puzzle state.[46]
Strict limit mode
Implemented in Sokoban Limit, the objective is to solve a puzzle with a very strict number of moves, which transforms seemingly simple puzzles into an efficiency challenge.[47]

Computer science research

Sokoban has been studied using the theory of computational complexity. The computational problem of solving Sokoban puzzles was first shown to be NP-hard.[48][49] Further work proved it is also PSPACE-complete.[50][51]

Solving non-trivial Sokoban puzzles is difficult for computers because of the high branching factor (many legal pushes at each turn) and the large search depth (many pushes needed to reach a solution).[52][53] Even small puzzles can require lengthy solutions.[54]

The Sokoban game provides a challenging testbed for developing and evaluating planning techniques.[55] 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.[56][57] A later solver, Festival, introduced the FESS search algorithm and became the first automatic system to solve all 90 puzzles in the widely used XSokoban test suite.[58][59] Despite these advances, even the most sophisticated solvers cannot solve many highly complex puzzles that humans can solve with time and effort, using their ability to plan ahead, recognize patterns, and reason about long-term consequences.[60][61][62]

See also

Notes

  1. ^ Japanese: 倉庫番, Hepburn: Sōko-ban; lit. 'warehouse keeper'[1]

References

  1. ^ Yoshio Murase; Hitoshi Matsubara; Yuzuru Hiraga (1996). Norman Foo; Randy Goebel (eds.). Automatic Making of Sokoban Problems. Springer Science & Business Media. p. 592. ISBN 978-3-540-61532-3.
  2. ^ 倉庫番. MICOMGAMES (in Japanese). Vol. 1, no. 1. December 1983. p. 38. 考えずにスイスイ荷物を動 かすと, 最後は必ず行き詰まる。 倉庫番で最 も重要なのは、最初の一手、この一手を実行 する前に、先の先まで読み切ることが大切。 [If you move boxes around without thinking ahead, you will inevitably end up at a dead end. In Sokoban, the most critical move is the very first one — before making it, you must think several moves ahead and visualize all possible outcomes.]
  3. ^ Jean-Noël Demaret; François Van Lishout; Pascal Gribomont (2008). Hierarchical Planning and Learning for Automatic Solving of Sokoban Problems (PDF). pp. 1, 2. a bad move can lead in Sokoban to a deadlock, a situation in which the solution game state is not reachable anymore.
  4. ^ "こうなるとアウトだよ" [If it gets to this, it's unsolvable]. ja:ファミコン通信 (in Japanese). July 1986. p. 30.
  5. ^ "ごあいさつ" [Greetings]. Sokoban.jp (in Japanese). Falcon Co., Ltd. 「倉庫番」が生まれたのは1981年の桜の花びらが舞う春でした。 [Sokoban was born in the spring of 1981 [in Japan], when cherry blossoms danced through the air.]
  6. ^ 考えるウサギはパソコンの野を駆ける！ [The thinking rabbit runs through the fields of the computer!]. ログイン (雑誌) (in Japanese). December 1983. pp. 136–139. そのPC-8001で作ったゲームの中に シンキングラビットの第1作であり、 現在もヒット中の"倉庫番" の原型が ある。内容はほぼ同じだが、○×□の キャラクタ表示で画数は5面。 友人知 人を家に集めては、 内輪で楽しんでい たものだ。 ゲームセンスの卓抜さは、 3年前すでに目立っていたのである。 近くにある妻の実家のレコード店に、 パソコンコーナーを設けるという話が もちあがりまして、 直接僕はタッチし てなかったんですが、 そのとき倉庫 番"を見て、これは売れる!と助言 してくれた人がいたんです」 パソコンコーナーに入ったPC-8801 を利用して、デザインを決めグラフィ ックスをきれいにして、 20面まで制作。 [Among the games developed for the PC-8001 was the prototype of Sokoban, the first title by Thinking Rabbit and a game that is still popular today. The core design was nearly identical to the commercial release, but used text characters (○, ×, and □) for display and had only five levels. The creator, Hiroyuki Imabayashi, often invited friends to his home to play the game, where it became a hit in private circles. His exceptional game design skills had been evident since at least three years earlier. Around that time, plans came up to add a computer section to a nearby record store owned by Imabayashi's wife's family. Though not directly involved, Imabayashi received pivotal feedback when an observer saw Sokoban and insisted, "This will sell!" Using the more advanced PC-8801 from the store's computer corner, he enhanced the graphics, polished the design, and expanded the game to 20 levels.]
  7. ^ "Thinking Rabbit - 1983 Developer Interview".
  8. ^ "My conversation with Mr Hiroyuki Imabayashi".
  9. ^ Austin Barr; Calvin Chung; Aaron Williams (2021). Block Dude Puzzles are NP-Hard (and the Rugs Really Tie the Reductions Together) (PDF). CCCG (2021). p. 1. Spectrum Holobyte published the game under the name Soko-Ban for American personal computers in 1988, which was the same year it brought Tetris to the same platform.
  10. ^ "Put Your Brain Action". Electronic Gaming Monthly. No. 10. Sendai Publishing. May 1990. p. 17.
  11. ^ "Boxxle II". GB Action. No. 4. Future Publishing. September 1992. p. 20.
  12. ^ Kyuukuoku No Sokoban (Instruction manual). Itochu. 1996.
  13. ^ "Sokoban Official Site". Sokoban.jp (in Japanese). Retrieved August 19, 2025. "倉庫番", "sokoban", the rabbit mark and "THINKING RABBIT" are trademarks or registered trademarks of Falcon co.,ltd. in Japan and other countries. [...] COPYRIGHT©2001 FALCON CO.,LTD. ALL RIGHTS RESERVED.
  14. ^ "倉庫番の歴史" [The History of Sokoban] (in Japanese). Retrieved June 2, 2025.
  15. ^ 倉庫番. MICOMGAMES (in Japanese). Vol. 1, no. 1. December 1983. p. 38. 一度やりだしたらなかなかやめられない。 [Once you start playing, it's hard to stop.]
  16. ^ 倉庫番. ja:パソコンゲームランキングブック. October 1983. p. 28.: scored the game 94 points out of 100.
  17. ^ 倉庫番[番外編]. PCマガジン (in Japanese). August 1983. pp. 52–56. 今回はこのゲームを開発した THINKING RABBIT さんにお願いして, 市販品とは別に10の倉庫をつくってもらいましたので [This time, we asked THINKING RABBIT, the developer of this game, to build 10 warehouses separately from commercial release]
  18. ^ 倉庫番2. ログイン (雑誌) (in Japanese). July 1985. p. 76. パズルソフトのベストセラー倉庫番の新たな50面と迷路エディタがついた倉庫番 2 。 [Sokoban 2, the sequel to the bestselling puzzle game Sokoban, includes 50 new levels and a maze editor.]
  19. ^ Lesser, Hartley; Lesser, Patricia; Lesser, Kirk (April 1988). "The Role of Computers". Dragon. No. 132. p. 84.: reviewers rated the game 4+1⁄2 out of 5 stars.
  20. ^ ソフトハウス訪問 [Visiting a Software Company]. POPCOM (in Japanese). June 1984. p. 131.
  21. ^ 作者が語る自信のニューソフト [The creator proudly presents their new software]. POPCOM (in Japanese). March 1985. p. 29.
  22. ^ Lafe Low (November 1988). "News Line; Made in Japan". inCider. p. 14.
  23. ^ Given that Soko-Ban was licensed to Spectrum Holobyte by ASCII Corporation, which published console versions, like Famicom and MSX, but not the original 1982 release, the number may reflect cumulative sales across multiple Japanese titles, though the source does not specify.Soko-Ban (Media notes). Spectrum Holobyte. 1988. p. box. Licensed from ASCII Corporation.
  24. ^ Wagner, Roy (May 1988). "Puzzling Encounters" (PDF). Computer Gaming World. No. 47. pp. 42–43.
  25. ^ Marçal Mora Cantallops (2023). Rompecabezas: Cinco décadas de videojuegos y puzles (in Spanish). Héroes De Papel. ISBN 978-84-947149-3-1. la web está llena de múltiples clones de Sokoban [the web is full of multiple Sokoban clones]
  26. ^ Austin Barr; Calvin Chung; Aaron Williams (2021). Block Dude Puzzles are NP-Hard (and the Rugs Really Tie the Reductions Together) (PDF). CCCG (2021). p. 1. the term "Sokoban" has become genericized
  27. ^ Petr Jarusek; Radek Pelánek (2010). "Difficulty Rating of Sokoban Puzzle". Frontiers in Artificial Intelligence and Applications. 222: 140–150. doi:10.3233/978-1-60750-675-1-140. There is a very large number of levels of the puzzle freely available on the Internet. These available levels span wide range of difficulty.
  28. ^ Several efficient Sokoban solvers aim to find short, but not necessarily optimal, solutions, including JSoko, YASS, and Takaken. Balyo, Tomáš; Froleyks, Nils (2022). "AI Assisted Design of Sokoban Puzzles Using Automated Planning". In Wölfel, Matthias; Bernhardt, Johannes; Thiel, Sonja (eds.). ArtsIT, Interactivity and Game Creation. Springer. pp. 429–430. doi:10.1007/978-3-030-95531-1_29. ISBN 978-3-030-95531-1.
  29. ^ Austin Barr; Calvin Chung; Aaron Williams (2021). Block Dude Puzzles are NP-Hard (and the Rugs Really Tie the Reductions Together) (PDF). CCCG (2021). p. 1. There are over 100 publications with "Sokoban" or "倉庫番" in the title, ranging from artificial intelligence solvers and optimizers, to level generation
  30. ^ Austin Barr; Calvin Chung; Aaron Williams (2021). Block Dude Puzzles are NP-Hard (and the Rugs Really Tie the Reductions Together) (PDF). CCCG (2021). p. 1. the term "Sokoban" [...] is synonymous with the genre of box-pushing puzzle games
  31. ^ Robert Aubrey Hearn (2006). Games, Puzzles, and Computation (PDF) (PhD thesis). Massachusetts Institute of Technology. p. 106.
  32. ^ David W. Skinner. "Hexoban". Archived from the original on April 3, 2002. Using hexagons, instead of squares as in standard Sokoban, offers a new realm of possibilities.
  33. ^ Alfred Pfeiffer. "Multiban". Archived from the original on March 9, 2005. the well known Sokoban game is extended to mazes that contain (often also require) more than one pusher.
  34. ^ Aymeric du Peloux. "Multicosmos". Archived from the original on June 16, 2025. I'm creating some new levels with two wharehousemen. Above, I illustrate a level where, to be solved, a penguin and a bear have to play alternately in cooperation. It's inspired of the Sokoban game of course
  35. ^ Gerald Holler. "SokoMind Plus is here!". Archived from the original on April 10, 2001. SokoMind Plus is a new game variant [...] boxes and target squares are marked with a number tag. Each box has to be placed on the target square with the same number.
  36. ^ Crystal Shard. "Block-O-Mania". Archived from the original on October 29, 2005. The object of the game is to push all blocks onto the right storages: red blocks onto red storages, green on green, and blue on blue.
  37. ^ Mark Mainwood. "Interlock". Archived from the original on February 6, 2007. Use the ball to push like-coloured blocks together.
  38. ^ Games4Brains. "Sokolor". Archived from the original on February 7, 2000. Tiles of the same colour need to be pushed together{{cite web}}: CS1 maint: numeric names: authors list (link)
  39. ^ Doug Beeferman. "CyberBox". Archived from the original on December 12, 1998. Avoid trapping yourself or blocking an exit with careful forethought.
  40. ^ a b "Picoban". Archived from the original on August 1, 2025. Retrieved August 1, 2025. Picoban is a sokoban-style puzzle game [...] the red orbs need to be moved onto buttons and that keys need to be collected before you can make it to the green teleport stone.
  41. ^ Ziwen Liu; Yang Chao (2017). "The Non-Deterministic Constraint Logic and Its Applications in Computational Complexity" (PDF). Computer Science and Application (in Chinese). 7. Hans Publishers: 407–413. doi:10.12677/csa.2017.75049. Retrieved June 4, 2025.
  42. ^ Games4Brains. "Sokonex". Archived from the original on February 7, 2000. Push all Connector-tiles together! Don't be disturbed by movable lasers, holes in the ground and broken plates.{{cite web}}: CS1 maint: numeric names: authors list (link)
  43. ^ Doug Beeferman. "Cyberbox". Archived from the original on December 12, 1998. Push and get pushed by blocks with various functions.
  44. ^ Crystal Shard. "Block-O-Mania". Archived from the original on October 29, 2005. Your progress will be hindered by one-arrows, one-time passages that turn into solid walls after you pass through them, and many other devious traps.
  45. ^ Zubaran, Tadeu; Ritt, Marcus (2011). Agent motion planning with pull and push moves (PDF). 8th National Meeting on Artificial Intelligence (ENIAC 2011). Sociedade Brasileira de Computação. pp. 358–369. Archived from the original (PDF) on April 16, 2024. Retrieved June 16, 2025. Pukoban is a game on an integer grid [...] The agent can push or pull a box one cell horizontally or vertically if the destination cell is free and he has enough space to do so.
  46. ^ "Feature list: Game Play". Sokoban Wiki. Retrieved August 14, 2025. reverse mode play starting at end position (pull instead of push)
  47. ^ "Sokoban Limit". Retrieved August 18, 2025. This Sokoban game has a very strict moves limit
  48. ^ Michael Fryers; Michael Greene (1995). "Sokoban" (PDF). Eureka (54): 25–32. Archived from the original (PDF) on September 5, 2024.
  49. ^ Dorit Dor; Uri Zwick (1999). "SOKOBAN and other motion planning problems". Computational Geometry. 13 (4): 215–228. doi:10.1016/S0925-7721(99)00017-6.
  50. ^ Joseph C. Culberson (1997). "Sokoban is PSPACE-complete" (PDF). Technical Report TR 97-02, Dept. Of Computing Science, University of Alberta. Archived from the original (PDF) on May 28, 2024.
  51. ^ Robert Aubrey Hearn (2006). Games, Puzzles, and Computation (PDF) (PhD thesis). Massachusetts Institute of Technology. pp. 98–100.
  52. ^ Andreas Junghanns; Jonathan Schaeffer (2001). "Sokoban: Improving the Search with Relevance Cuts" (PDF). Theoretical Computer Science. 252 (1–2): 5. doi:10.1016/S0304-3975(00)00080-3.
  53. ^ Yaron Shoham (2020). "FESS Draft" (PDF). p. 3.
  54. ^ David Holland; Yaron Shoham. "Theoretical analysis on Picokosmos 17". Archived from the original on June 7, 2016.
  55. ^ Timo Virkkala (2011). Solving Sokoban (PDF) (MSc thesis). University of Helsinki. p. 1.
  56. ^ Andreas Junghanns (1999). Pushing the Limits: New Developments in Single-Agent Search (PhD thesis). University of Alberta. doi:10.7939/R3W95103S.
  57. ^ Andreas Junghanns; Jonathan Schaeffer (2001). "Sokoban: Enhancing general single-agent search methods using domain knowledge". Artificial Intelligence. 129 (1–2): 219–251. doi:10.1016/S0004-3702(01)00109-6.
  58. ^ Yaron Shoham; Jonathan Shaeffer (2020). The FESS Algorithm: A Feature Based Approach to Single-Agent Search (PDF). 2020 IEEE Conference on Games (CoG). Osaka, Japan: IEEE. doi:10.1109/CoG47356.2020.9231929.
  59. ^ Yaron Shoham (2020). "FESS presentation at the CoG conference (17.5 minutes)" (video). archive.org.
  60. ^ Petr Jarusek; Radek Pelánek (2010). "Difficulty Rating of Sokoban Puzzle". Frontiers in Artificial Intelligence and Applications. 222: 140–150. doi:10.3233/978-1-60750-675-1-140. There exist small instances that can be quickly solved by computer (using a trivial brute force algorithm) but take humans hours to solve. At the same time, there are also instances of the puzzle, which humans can solve but which are beyond capabilities of [...] artificial intelligence solvers.
  61. ^ "Let's Logic Bots Statistics" (PDF). Retrieved October 6, 2024.
  62. ^ "Sokoban Solver Statistics - Large Test Suite". Retrieved April 14, 2024.
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