Puzzle format

From Sokoban Wiki

The most commonly used format for representing a level of Sokoban is:

Level element	Character	ASCII Code
Wall	#	0x23
Player	@	0x40
Player on goal square	+	0x2b
Box	$	0x24
Box on goal square	*	0x2a
Goal square	.	0x2e
Floor	(Space)	0x20

The simplest solvable level looks like this:

#####
#@$.#
#####

It's important that the whole level is surrounded by walls (#) There are various different level formats. Many of them also offer the possibility to store save games or solutions in a level file.

A solution is represented by the movements of the player. The player can move up, down, left or right. Hence, the letters for these directions are: u, d, l, r. ⇒ Solution format

A possible solution string may look like this: DDrdrruLruLLDllU

The capitals in this solution show that a box is pushed as the player moves. Usually this information is stored in a solution, too, although the solution is still correct if all letters are lowercase.

Exchange of Sokoban levels in Emails

Lots of email servers strips empty spaces and multiple spaces, too. To ensure the levels can be imported to the email recipients properly here are some suggestions:

Replace all spaces by hyphens "-" or underscores "_" (preferred). (the recipients of your mail have to replace them back to spaces in order to import the levels to their Sokoban programs. However, some of the Sokoban games do have already an automatic replacement build in and can read the levels)

Run length encoding

The XSB format with RLE (run-length-encoding), is more compact, and efficient in mobile devices (as Palm, PocketPC, Smart Phones), besides being smaller to send for SMS. It can be used for both: levels and solutions.

In this format a digit shows how many elements of the same type are following.

#### becomes 4#

This level ("Claire", by Lee J Haywood):

#######
#.@ # #
#$* $ #
#   $ #
# ..  #
#  *  #
#######

runlength encoded looks like this:

7#|#.@-#-#|#$*-$-#|#3-$-#|#-..--#|#--*--#|7#

The rows of the level are separated by "|"s. There has been a discussion in the Yahoo Group about what character should represent an empty square in May 2006. Finally the hyphen has been elected to be the standard character for an empty square. Nevertheless, programs are encouraged to support both, hyphens and underscores.

If only two level elements are grouped together they may be run length encoded, but needn't to. Example:

$$ may keep $$ or be encoded as 2$

It's recommended to write run-length encoded boards in a single line because currently some programs may not be able to handle RLE-boards spanning multiple lines. Most of the editor programs (for instance "notepad" in Windows) have a automatic wrapping of lines so there is no need for manually creating new lines. However, when a RLE board spans multiple lines, the trailing "|" on each line may be omitted.

In the RLE format empty squares at the end of a row should be ommited.
For example, this level:

###__  <- two empty squares / spaces at the end of the row
#.###
#*$ #
# @ #
#####

Should be RLE this way:

3#|#.3#|#*$-#|#--@#|5#