Sokoban: A Classic Puzzle Game from Japan
If you are looking for a simple yet challenging puzzle game that can test your logic and planning skills, you might want to try Sokoban. Sokoban is a classic puzzle game that originated in Japan in the early 1980s. It has since become one of the most popular and influential puzzle games of all time, with many variants, implementations, and levels. In this article, we will introduce you to the basics of Sokoban, how to play it, what are the different variants, and why it is interesting for artificial intelligence research.
sokoban
What is Sokoban?
Sokoban (倉庫番, Sōko-ban, lit. 'warehouse keeper') is a puzzle video game in which the player pushes boxes around in a warehouse, trying to get them to storage locations. The game was designed in 1981 by Hiroyuki Imabayashi, and first published in December 1982 by Thinking Rabbit, a software house based in Takarazuka, Japan.
The rules of the game
The game is played on a board of squares, where each square is a floor or a wall. Some floor squares contain boxes, and some floor squares are marked as storage locations. The player is confined to the board and may move horizontally or vertically onto empty squares (never through walls or boxes). The player can move a box by walking up to it and push it to the square beyond. Boxes cannot be pulled, and they cannot be pushed to squares with walls or other boxes. The number of boxes equals the number of storage locations. The puzzle is solved when all boxes are placed at storage locations.
The history of the game
Sokoban was created in 1981 by Hiroyuki Imabayashi. The first commercial game was published in December 1982 by Thinking Rabbit, a software house based in Takarazuka, Japan. Sokoban was a hit in Japan where it sold more than 400,000 copies before being released in the United States. In 1988, Sokoban was published in US by Spectrum HoloByte for the Commodore 64, IBM PC compatibles, Amiga, and Apple II as Soko-Ban. Since then, Sokoban has been ported to numerous computer platforms, including almost all home computer and personal computer systems. Different versions also exist for video game consoles, mobile phones, graphic calculators, digital cameras [citation needed] and electronic organizers.
The popularity of the game
Sokoban is one of the most popular thought and logic games. The name comes from Japan and means "warehouse keeper". As simple as that name is, so is the idea of this game: A level represents a store room, where boxes appear to be randomly placed. You help the warehouse keeper to push the boxes around the maze of the room so that, at the end, all boxes are on marked fields. The only restrictions are that the warehouse keeper can only push a box, never pull, and that just one box may be pushed at a time. Each level has a different structure, which requires a different solution - often with a different strategy as well. The magic of the game is that boxes, which are out of the way on one move, might be in the way on the next move. The simplicity of the rules, in combination with the complexity of the puzzles, makes Sokoban one of the most addictive games ever. There are more than 20,000 different levels available for Sokoban, with varying degrees of difficulty, and still growing. The game is also known as Warehouse Keeper, Boxman, Boxworld or Push Box in some countries.
How to play Sokoban?
Playing Sokoban is easy. You just need a device that can run the game, such as a computer, a smartphone, or a tablet. You can also play online on some websites that offer Sokoban games. The game usually starts with a simple level that teaches you the basic rules and controls. You can use the arrow keys or the mouse to move the warehouse keeper and push the boxes. You can also undo your moves if you make a mistake or restart the level if you get stuck. The goal is to push all the boxes to the storage locations in the minimum number of moves possible. The game will keep track of your moves and time, and show you your score and rank at the end of each level. You can also compare your scores with other players online or challenge yourself with harder levels.
Basic tips and strategies
Sokoban may seem simple at first, but it can be very tricky and challenging as you progress. Here are some basic tips and strategies that can help you solve the puzzles more efficiently:
Plan ahead. Before you start pushing boxes, try to visualize the final position of each box and the path you need to take to get there. Avoid pushing boxes to corners or dead ends where they cannot be moved anymore.
Think backwards. Sometimes it is easier to start from the goal and work backwards to find the best way to move the boxes. This can help you avoid unnecessary moves or traps.
Use shortcuts. Some levels have shortcuts or alternative routes that can save you time and moves. Look for them and use them wisely.
Learn from your mistakes. If you get stuck or make a wrong move, don't give up. Use the undo function or restart the level and try again. You can also look for hints or solutions online if you need some help.
Sokoban programs and websites
There are many Sokoban programs and websites that you can use to play the game on different devices and platforms. Here are some of them:
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Name
Description
URL
Sokoban Online
A website that offers thousands of Sokoban levels for free, with online ranking, achievements, and community features.
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Sokoban YASC
A program that runs on Windows computers, with many features such as unlimited undo/redo, mouse support, level editor, solver, optimizer, and more.
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Sokoban++
A program that runs on Windows computers, with a simple interface and a large collection of levels.
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Sokoban Pro
A program that runs on Android devices, with smooth graphics and sound effects, multiple skins, and 450 levels.
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Sokoban Land DX
A program that runs on iOS devices, with colorful graphics and animations, 100 levels, and 5 different worlds.
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Sokoban levels and puzzles
As mentioned before, there are more than 20,000 different Sokoban levels available for the game, with varying degrees of difficulty and complexity. Some of them are original levels created by Hiroyuki Imabayashi or other designers, while others are based on existing puzzles or games such as chess, mazes, crosswords, etc. Some levels are also inspired by real-life situations or objects such as buildings, animals, plants, etc. Some levels are easy and can be solved in a few moves, while others are hard and can take hours or even days to solve. Some levels have multiple solutions, while others have only one solution. Some levels are symmetrical, while others are asymmetrical. Some levels are regular, while others are irregular. Some levels are small, while others are large. Some levels are simple, while others are complex. In short, there is a Sokoban level for everyone and every taste.
Here are some examples of Sokoban levels and puzzles:
Level
Puzzle
Solution
Original Level 1
Original Level 10
Chess Puzzle
Maze Puzzle
Flower Puzzle
What are the variants of Sokoban?
Sokoban has inspired many variants and extensions that add new elements or modify the rules of the original game. Some of these variants are:
Hexoban and Trioban
Hexoban and Trioban are variants of Sokoban that use hexagonal and triangular grids instead of square grids. This changes the geometry and the number of possible directions for moving and pushing boxes. Hexoban has six directions, while Trioban has three directions. These variants introduce new challenges and possibilities for designing and solving puzzles.
Multiban and Interlock
Multiban and Interlock are variants of Sokoban that involve multiple warehouse keepers or multiple types of boxes. In Multiban, the player can switch between different warehouse keepers that can cooperate to push boxes. In Interlock, the player has to deal with different colors or shapes of boxes that can only be pushed to matching storage locations. These variants increase the complexity and the diversity of the puzzles and require more coordination and logic.
Numbered Sokoban and Modern Sokoban
Numbered Sokoban and Modern Sokoban are variants of Sokoban that introduce new constraints or objectives for the game. In Numbered Sokoban, the boxes and the storage locations are numbered, and the player has to match them in ascending order. In Modern Sokoban, the player has to push the boxes to the storage locations in a specific order, which is indicated by arrows or symbols on the floor. These variants add more difficulty and challenge to the game and require more memory and planning.
Why is Sokoban interesting for artificial intelligence research?
Sokoban is not only a fun and addictive game for humans, but also a fascinating and challenging problem for artificial intelligence research. Sokoban puzzles have many properties that make them suitable for studying and testing various aspects of artificial intelligence, such as:
The complexity of Sokoban puzzles
Sokoban puzzles are known to be NP-hard, which means that there is no efficient algorithm that can solve them in polynomial time. In fact, some Sokoban puzzles are PSPACE-complete, which means that they are among the hardest problems in computational complexity theory. Solving Sokoban puzzles requires a lot of computation and memory resources, and even humans can have a hard time finding optimal solutions. Therefore, Sokoban puzzles are a good benchmark for measuring the performance and scalability of artificial intelligence systems.
The algorithms and heuristics for solving Sokoban puzzles
Sokoban puzzles can be solved by using various algorithms and heuristics that employ different techniques and strategies. Some of the most common methods are:
Search algorithms: These algorithms explore the state space of the game, which consists of all possible configurations of the board, boxes, and warehouse keeper. They use different criteria to select which states to expand and which ones to prune, such as depth-first search, breadth-first search, best-first search, A*, IDA*, etc.
Heuristic functions: These functions estimate the distance or the cost from a given state to the goal state, which can help guide the search algorithms towards better solutions. They use different measures to evaluate the difficulty or the progress of a state, such as Manhattan distance, deadlock detection, box ordering, etc.
Pattern databases: These databases store precomputed information about subproblems or partial solutions of Sokoban puzzles, which can be used to speed up the search algorithms or improve the heuristic functions. They use different methods to decompose or abstract the puzzles, such as macro moves, disjoint sets, symmetry reduction, etc.
The applications and challenges of Sokoban solvers
Sokoban solvers are not only useful for playing or designing Sokoban puzzles, but also for solving other problems that have similar characteristics or structures. For example, Sokoban solvers can be applied to:
Robotics: Solving Sokoban puzzles can be seen as a simplified version of robot motion planning or manipulation problems, where a robot has to move objects around in a constrained environment.
Logistics: Solving Sokoban puzzles can be seen as a simplified version of logistics or transportation problems, where goods have to be delivered or stored in a warehouse or a container.
Games: Solving Sokoban puzzles can be seen as a simplified version of other games or puzzles that involve moving or pushing objects around, such as sliding tile puzzles, Rubik's cube, etc.
However, Sokoban solvers also face many challenges and limitations that prevent them from solving all possible Sokoban puzzles or generalizing to other problems. Some of these challenges are:
The size and complexity of the state space: The number of possible states in a Sokoban puzzle grows exponentially with the size of the board and the number of boxes. This makes it impossible to explore or store all states in memory or disk.
The difficulty of finding optimal solutions: The optimal solution for a Sokoban puzzle is the one that uses the minimum number of moves to push all boxes to storage locations. However, finding such a solution is very hard and time-consuming, especially for large or complex puzzles. Therefore, most solvers settle for suboptimal solutions that are good enough but not optimal.
The lack of domain knowledge: The rules and goals of Sokoban are very simple and generic, which makes it easy to apply them to different problems. However, this also means that sokoban solvers do not have any domain knowledge or specific information about the problem they are solving. This makes it hard for them to exploit any structure or regularity in the puzzles or the problems, or to use any common sense or intuition that humans have.
Conclusion
Sokoban is a classic puzzle game that has been around for more than 40 years and still attracts millions of fans and players around the world. Sokoban is simple to learn but hard to master, and offers endless challenges and fun for puzzle lovers of all ages and levels. Sokoban is also a fascinating and challenging problem for artificial intelligence research, and has inspired many variants and extensions that add new elements or modify the rules of the original game. If you have never played Sokoban before, we encourage you to give it a try and see for yourself why it is one of the most popular and influential puzzle games of all time.
FAQs
Here are some frequently asked questions about Sokoban:
Q: Who invented Sokoban?
A: Sokoban was invented in 1981 by Hiroyuki Imabayashi, a Japanese computer programmer and game designer. He designed the game as a hobby and submitted it to a software contest organized by a magazine. He won the first prize and later founded his own company, Thinking Rabbit, to publish the game.
Q: How many Sokoban levels are there?
A: There are more than 20,000 different Sokoban levels available for the game, with varying degrees of difficulty and complexity. Some of them are original levels created by Hiroyuki Imabayashi or other designers, while others are based on existing puzzles or games such as chess, mazes, crosswords, etc. Some levels are also inspired by real-life situations or objects such as buildings, animals, plants, etc.
Q: What is the hardest Sokoban level?
A: There is no definitive answer to this question, as different levels may have different criteria for measuring their difficulty, such as the number of moves, the number of boxes, the size of the board, the symmetry of the puzzle, etc. However, some of the most notorious and challenging levels are:
Level 90 from Original Collection: This level requires 306 moves to solve optimally, which is the highest number among all original levels. It also has 20 boxes and a large board with many walls and dead ends.
Level 11 from Sasquatch Collection: This level requires 126 moves to solve optimally, which is not very high compared to other levels. However, it has a very complex and irregular structure that makes it very hard to find a solution.
Level 15 from Microban Collection: This level requires only 20 moves to solve optimally, which is very low compared to other levels. However, it has a very tight and symmetrical structure that makes it very easy to make a mistake or get stuck.
Q: How can I create my own Sokoban levels?
A: There are many tools and programs that you can use to create your own Sokoban levels. Some of them are:
Sokofun: A program that runs on Windows computers, with a level editor that allows you to create and test your own levels. You can also play existing levels or download new ones from the internet.
SokEdit: A program that runs on Windows computers, with a level editor that allows you to create and edit your own levels. You can also import and export levels in various formats.
SokEvo: A website that allows you to create and play your own levels online. You can also share your levels with other users or browse through thousands of levels created by others.
Q: How can I improve my Sokoban skills?
A: The best way to improve your Sokoban skills is to practice and play more levels. You can also learn from other players or solvers by watching their solutions or reading their tips and strategies. You can also try different variants or extensions of Sokoban that can challenge you in new ways or teach you new skills. 44f88ac181
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