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https://github.com/smartive/rust-sokoban-level-generator

A procedural level generator for "sokoban".
https://github.com/smartive/rust-sokoban-level-generator

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A procedural level generator for "sokoban".

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# Sokoban Level Generator in Rust



This is a sokoban level generator algorithm written in rust to procedurally

generate levels for the game [Sokoban](https://en.wikipedia.org/wiki/Sokoban).



The algorithm is based on the following resources:



- [Procedural Generation of Sokoban Levels](http://ianparberry.com/techreports/LARC-2011-01.pdf);

  a technical report by Joshua Taylor and Ian Parberry.

- [Sokoban-Level-Generator](https://github.com/AlliBalliBaba/Sokoban-Level-Generator);

  a javascript implementation by AlliBalliBaba.



## Usage



In order to use the generator, add this library (via git) to your project

with cargo. Then, import the level generator and use it to generate

a level. The ``level_to_string`` method allows you to print the level

in the [JSoko Level Format](https://www.sokoban-online.de/sokoban/levell-format/).



```rust

use sokoban_level_generator::{generate_level, level_to_string};



fn main() {

    let level = generate_level(4, 4, 3);

    println!("Print level");

    println!("{}", level_to_string(&level));

}

```



The algorithm uses randomness to generate levels and needs

to create the "farthest state possible" for boxes. As such,

generation with more boxes can take a very long time. See the

benchmarks section for more information.



**Warning**: Currently, there is no abort limit. So, trying to

generate impossible levels (e.g. 1x1 with 4 boxes) will result

in an infinite loop.



## Algorithm



The algorithm performs the following (high-level) steps:



1. Generate an empty level with ``width * 3`` and ``height * 3`` dimensions, since every "room" is 3x3.

2. Generate rooms in the level (by using the described templates in the paper); rooms are randomly selected and rotated

3. After the level is generated, check the level for:

    - Enough space

    - Enough goal possibilities (to place goals)

    - No large spaces (this does not generate interesting levels)

    - All floors are connected

    - No surrounded floors

4. Generate random goal locations

5. Calculate the "farthest state possible" for each box/player position

6. Return the farthest possible level



## Benchmarks



Benchmarks show that the algorithm is very fast for small levels, but

can take a very long time for larger levels. The biggest impact on

generation time is the number of boxes.



The result in short: feasible, interesting levels can be generated with

up to 4 boxes in a reasonable amount of time. The height / width of the

level should be kept below or equal to 3. If 3 or fewer boxes are used,

the level can be up to 4x4 in size. Bigger sizes must be experimented with.



The following tables shows the generation time for different level sizes.



### 1 Box

| Width | Height | Median Time |

|-------|--------|-------------|

| 1     | 1      | 5.7706 µs   |

| 1     | 2      | 19.403 µs   |

| 2     | 2      | 84.277 µs   |

| 2     | 3      | 4.3456 ms   |

| 3     | 3      | 1.3252 ms   |

| 3     | 4      | 6.3146 ms   |

| 4     | 4      | 33.759 ms   |



### 2 Boxes

| Width | Height | Median Time |

|-------|--------|-------------|

| 1     | 2      | 36.320 µs   |

| 2     | 2      | 241.53 ms   |

| 3     | 2      | 798.81 µs   |

| 3     | 3      | 2.9076 ms   |

| 4     | 3      | 10.201 ms   |

| 4     | 4      | 42.901 ms   |



### 3 Boxes

| Width | Height | Median Time |

|-------|--------|-------------|

| 2     | 3      | 4.3456 ms   |

| 3     | 3      | 20.324 ms   |

| 3     | 4      | 50.916 ms   |

| 4     | 4      | 227.51 ms   |



### Violin Plot (1-3 Boxes)



![Violin Plot](./res/violin.svg)



As we can see in the violin plot, the number of boxes has a huge impact on the generation time.