Sokoban

Template:Short description Template:Use mdy dates Template:Infobox video game series Template:Nihongo foot 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 hobby, and the following year, his company Thinking Rabbit published an enhanced commercial version in Japan for the NEC PC-8801 computer. Over the years, new titles were released for various platforms, developed by Thinking Rabbit or other companies under license. The game became popular in Japan and internationally, and the official series has remained active, with its most recent title released in 2021. Sokoban has inspired unofficial versions, thousands of custom puzzles, similar games, and artificial intelligence research.

File:Sokoban ani.gif

A Sokoban puzzle being solved

History

In 1981, Hiroyuki Imabayashi created the first Sokoban game as a hobby for the NEC PC-8001 computer. The game used text-based graphics and featured five levels designed by him. For the core mechanic, he was inspired by a part of the gameplay in Hudson Soft's 1980 action game, Aldebaran #1, for the MZ-80K, where the player pushed luggage to act as a wall to prevent radiation. Imabayashi conceptualized that in the warehouse, the boxes had to be organized, but they themselves also became obstacles in the process. He worked on designing levels that provided a real challenge, and friends he invited to his home to play the game struggled to solve them. At that time, his wife's parents owned a record store with a small computer section. By chance, a salesman saw the game and suggested that it would sell. Imabayashi used a NEC PC-8801 computer in the store's computer section to port the game, enhancing the graphics and expanding the levels to twenty. In 1982, he founded his company, Thinking Rabbit, based in Takarazuka, Japan, and released this PC-8801 version as the first commercial Sokoban game in December.

In August 1983, the Japanese magazine PC Magazine published Sokoban Extra Edition as a type-in program featuring ten new puzzles. This game was developed by Thinking Rabbit under request.

In 1984, Thinking Rabbit published Sokoban 2, featuring a puzzle editor.

Throughout the rest of the 1980s, new titles appeared on a variety of Japanese platforms, including home computers such as the MSX and PC-9801, and video game consoles such as the Famicom, Sega SG-1000, Sega Mega Drive, and Game Boy. These releases were developed either by Thinking Rabbit or by other companies under license.

In 1987, Spectrum HoloByte, under license from ASCII, ported and adapted the MSX version of Sokoban to IBM PC, Apple II, and Commodore 64, adding features for the U.S. market. The game was released in the United States early in 1988 as Soko-Ban.

In Japan, further titles followed in the 1990s for the Super Famicom, Windows, Macintosh, and PlayStation.

Around 2000, Thinking Rabbit became inactive but remained a legal entity. In 2001, the Japanese software company Falcon acquired the copyright to the official Sokoban games and the trademarks for Sokoban and Thinking Rabbit, becoming the official developer and licensor of the series. From 2004 to 2007, Falcon developed several titles for Japanese mobile phones. Starting in 2015, it also developed several Sokoban titles for Windows and later the smartphone game Sokoban Touch, all published under the Thinking Rabbit brand.

Critical reception

PC-8801 versions

• • A December 1983 issue of MICOMGAMES wrote that the puzzle's concept is simple but requires thinking comparable to Go or Shogi, and that "once you start playing, it is hard to stop" (translated from Japanese). The game's originality was rated 90 out of 100.
  • In the PC Game Ranking Book, the game received a score of 94 out of 100 points.

    Total Point	94
    Item	Difficulty	Addictiveness	Story	Originality	Value for money
    Stars (maximum 5)	4	5	5	5	5

IBM PC, Commodore 64, Apple II versions

• Soko-Ban
  • In 1988, Soko-Ban received a positive review from Computer Gaming World for its IBM PC and Commodore 64 versions, which described the game as simple yet mentally challenging, and noted its addictive nature.
  • The German magazine Happy Computer in its January 1988 issue gave the IBM PC version a rating of 87 out of 100, and called it "a brilliant, relaxed logic puzzle that keeps you thinking without pressure" (translated from German).

    Item	Graphics	Sound and Music	Happy (magazine) Rating
    Score	78	16	87

  • In Dragon magazine's mini-reviews, Hartley, Patricia, and Kirk Lesser rated the IBM PC version 4.5 out of five stars.
  • In the Computer Entertainer newsletter, the Apple II version was recommended and received 3.5 out of four stars for graphics, with the same rating for gameplay and entertainment.

Famicom Disk System versions

• • In the Japanese Family Computer magazine's All Catalog supplement, it was called "a pioneering puzzle game" (translated from Japanese) and received 13.45 out of 25 points.

    Item	Characters	Music	Controls	Addictiveness	Originality	Overall
    Score	3.79	2.51	2.53	2.05	2.57	13.45

Game Boy versions

• Boxxle
  • In the June 1990 issue of Game Player's magazine, Tom R. Halfhill reviewed Boxxle, stating that it also required careful planning or plenty of trial and error (usually both). He noted that the game's gameplay could become repetitive because the only variations in the 108 screens were the number and arrangement of crates and the shape of the rooms.
• • Computer and Video Games magazine rated the game 88% overall, indicating it as one of the "simple but effective puzzle games" for Game Boy. It compared the game's addictiveness with Tetris, stating the game "is an infuriatingly addictive little title; not quite on a par with Tetris, but not far off."

    Item	Graphics	Sound	Value	Playability	Overall
    Score	82%	76%	81%	88%	88%

  • Famitsu gave it a score of 25 out of 40.
  • In the Japanese Family Computer magazine's All Catalog supplement, the game was described as having simple gameplay that made it great. The game received 18.78 out of 30 points.

    Item	Characters	Music	Controls	Addictiveness	Value for money	Originality	Overall
    Score	3.02	2.99	3.31	3.26	3.10	3.10	18.78

• • In the Japanese Family Computer magazine's All Catalog supplement, it was noted that this second installment was significantly more difficult. It received 17.65 out of 30 points.

    Item	Characters	Music	Controls	Addictiveness	Value for money	Originality	Overall
    Score	2.81	2.86	3.01	3.14	2.91	2.92	17.65

Sega Genesis versions

• Shove It!
  • In the June 1990 issue of Game Player's magazine, Tom R. Halfhill reviewed Shove It!, noting it was a challenging game that required players to plan their moves carefully and that its unhurried pace was a refreshing respite from frenzied action games. However, all 160 puzzles were essentially the same.
• • In the March 1990 issue of the Japanese magazine BEEP! Mega Drive, the game received a total score of 25 out of 40. Three of the four reviewers recommended it for puzzle enthusiasts. One reviewer questioned the release of Sokoban on the Mega Drive, wondering whether people would buy the console specifically to play a puzzle game; another appreciated the user-friendly gameplay but noted its dated feel; and one commented that he did not find the game's main selling points—enhanced art and its 250 levels that could take months to complete—particularly appealing.

    Item	Reviewer 1	Reviewer 2	Reviewer 3	Reviewer 4	Overall
    Score	5	6	8	6	25

  • Famitsu gave it a score of 23 out of 40.

Game Gear versions

• • Famitsu gave it a score of 25 out of 40.

TurboGrafx-16 versions

• Boxyboy
  • In the December 1990 issue of Game Player's magazine, Tom R. Halfhill reviewed Boxyboy, highlighting its logical, untimed puzzles and describing it as a welcome change from typical action games. He noted that it was "virtually identical" to Shove It! and Boxxle.
• • Famitsu gave it a score of 27 out of 40.

PlayStation versions

• • Famitsu gave it a score of 25 out of 40.
• • Famitsu gave it a score of 22 out of 40.
• • Famitsu gave it a score of 22 out of 40.

Games

Since its debut in 1982, Sokoban has been released on various platforms, primarily in Japan but also in other regions. Most titles are independent, though a few are sequels.

Titles in the Sokoban series

Region	Title	Release	Platform	Developer	Publisher
Japan		1982-1983	NEC PC-8801 NEC PC-6001mkII Sharp MZ-2000 Sharp X1	Thinking Rabbit	Thinking Rabbit
		1983	NEC PC-8801		Template:Ill
		1984	NEC PC-8801 NEC PC-8001mkII Fujitsu FM-7 Sharp X1		Thinking Rabbit
		1984	MSX	ASCII	ASCII
		1984	MSX
		1985	Game Pocket Computer	Epoch	Epoch
		1985	SG-1000	Sega	Sega
		1986	Famicom Disk System	ASCII	ASCII
		1989	NEC PC-9801 Sharp X68000 Sharp X1 MSX2 FM Towns	Thinking Rabbit	Thinking Rabbit
		1989	Game Boy	Atelier Double	Pony Canyon
		1990	Game Boy
		1990	Namco System 1	Namco	Namco
		1990	Sega Genesis	Template:Ill	Masaya
		1990	Game Gear	Thinking Rabbit	Riverhill Soft
		1990	TurboGrafx-16	Media Rings	Media Rings
		1991	NEC PC-9801	Thinking Rabbit	Thinking Rabbit
		1993	Super Famicom	Thinking Rabbit	Pack-In-Video
		1995	Windows	Thinking Rabbit	Itochu
		1996	Macintosh
		1996	PlayStation
		1997	Windows Macintosh
		1997	PlayStation
		1998	PlayStation
		1998	Windows
		1998	Windows
		1998	Windows	Thinking Rabbit	Template:Ill
		1999	Game Boy	J Wing	Template:Ill
		1999	Super Famicom	Atelier Double	Nintendo
		1999 2000	PlayStation Windows	Unbalance	Unbalance
		2000	Windows	Unbalance	Unbalance
		2004	EZweb i-mode	Falcon	Square Enix Dwango
	(1/2/3)	2004	EZweb		Square Enix
	(1-1/1-2/1-3/2-1/2-2/2-3/3-1/3-2/3-3)	2004-2005	i-mode		Dwango
		2007	i-mode	Konami	Konami
		2015	Windows	Falcon	Thinking Rabbit
		2015	Windows
		2016	Windows
		2016	Windows
		2018	Windows
North America	Soko-Ban	1988	IBM PC Commodore 64 Apple II	Spectrum HoloByte	Spectrum HoloByte
	Shove It! The Warehouse Game	1990	Sega Genesis	Template:Ill	DreamWorks
	Boxyboy	1990	TurboGrafx-16	Media Rings	NEC
	Boxxle	1990	Game Boy	Atelier Double	FCI
	Boxxle II	1992	Game Boy
Worldwide	Sokoban Touch	2016	Android iOS	Falcon	Thinking Rabbit
	The Sokoban	2021	Nintendo Switch PlayStation 4	Template:Ill	Unbalance

Name genericization

The name Sokoban is a registered trademark for video game titles. However, the core mechanic of pushing boxes to storage locations on a grid is not protected by intellectual property rights. This has enabled others to create many unofficial versions. Consequently, the term has become genericized, making it synonymous with the box-pushing puzzle genre established by the Sokoban titles by Thinking Rabbit and later adopted in games by others using the same core mechanic.

Cultural impact

The active fan community has created thousands of custom puzzles spanning a wide range of difficulty, as well as software tools, including puzzle editors, solvers, and solution optimizers.

Derivatives and variants

Official titles

A few official Sokoban games introduced modifications to the core mechanic of pushing boxes to storage locations in a warehouse.

• – includes a mode where you can use tools such as ropes.

• – features themed stages with either time limits, underwater boxes that can float up, disappearing boxes, or boxes with electrical wiring.

• – offers a story mode in which the player must push enemies into holes and push puppets onto magic circles.

• – an action-puzzle game in which the player shoot orbs and fill holes with rocks.

Similar games

Several games are based on Sokoban, introducing new mechanics or objectives. Examples include:

• Picoban – the goal is to reach a teleport stone, pushing orbs onto buttons or collecting keys.

• Beanstalk – different items must be pushed into a target square in a fixed sequence.

• Pukoban – the character can pull boxes.

• Sokoboxes Duo – two pushers must collaborate to solve the puzzle.

Variants

• Hexoban – uses a hexagonal grid instead of a square grid, allowing movements in six directions instead of four.

• Multiban – the puzzle contains more than one pusher.

Program features

Some unofficial Sokoban programs feature a "reverse mode" in which players play a puzzle backward. Starting with all boxes on storage locations, they pull the boxes to return to the initial puzzle state.

Gameplay

The game of Sokoban takes place in a warehouse, viewed from above, 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 marked as 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.

The player can move one square at a time, either horizontally or vertically, onto an empty floor square. 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.

Playing Sokoban requires thinking several steps ahead and visualizing all possible outcomes. Players should think carefully and thoroughly before pushing a box to prevent it getting trapped against a wall or other boxes. A bad move can cause a deadlock from which the puzzle cannot be solved, regardless of subsequent moves.

Deadlocks

Common deadlocks are:

File:Sokoban deadlocks.png

Two boxes are placed together along a wall. Each box blocks the other from being moved. A box in a corridor alongside a wall, which can still be pushed, but permanently lacks access to any storage location. A box in a corner. A box in a dead end. Four boxes in a square formation. Three boxes forming an L-shape in a wall corner.

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. Further work proved it is also PSPACE-complete.

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). Even small puzzles can require lengthy solutions.

The Sokoban game provides a challenging testbed for developing and evaluating planning techniques. 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. 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. 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.

Commercial success

The first Sokoban title was a commercial success in Japan, selling over 25,000 copies by July 1984.

Early Sokoban titles released for numerous Japanese home computer systems such as the NEC PC-9801 and Sharp X1 were a hit, selling over 100,000 copies in total.

Spectrum Holobyte acknowledged that before 1988, over 400,000 copies of the game were sold in Japan, considering it a commercial success. This figure referred to the Japanese Sokoban title for MSX published by ASCII in 1984. The U.S. Soko-Ban title, sold over 50,000 units by mid-September of 1988.

See also

• Logic puzzle
• Sliding puzzle
• Transport puzzle
• Motion planning

External links

• Official Sokoban site (in Japanese)
• The University of Alberta Sokoban page