A collection is a text file (.txt extension) lovalted in the Levels directory. It may contain as many levels as necessary.
The collection files are subject to the following format :
Fixed Header:
6 lines.
the 1st, 3rd, 4th, 5th and 6th start with a ';'
the 2nd is empty
they are used for title and autoring information
Variable Header
any number of lines
they are used for comments
Header Termination
2 lines
the 1st is ' ' (2 spaces)
the 2nd is empty
Levels(any number)
Level Title
1 line
starts with a ';'
Level Data
1 line per row of tile
each character in each line represents a tile:
' ' (space) = nothing
'#' = Wall
'.' = Goal
'$' = Box
'@' = starting position
'*' = Goal + Box
'+' = Goal + starting position
Level Termination
1 line
it is empty
Knowing that, you can write your own devious levels... or download them from the web.
There are a lot of them at
http://www.sourcecode.se/sokoban/levels.php. Only get them in plain text format.