# Unsolvable Levels

YSokoban has support for unsolvable levels. Unfortunately, there are "collectors" out there who collects everything, including unsolvable levels (levels which are proven to be unsolvable). What's worst, is that these collectors also share their collection to others un-modified... As a result, we have some unsolvable levels in circulation which are well known, but still show up in some collections. One possible way to deal with this levels is to keep them in a special unsolvable collection and use some tool (like SokoDUP) to see whether new collection has such kind of unsolvable levels. The other possible solution is to let YSokoban know about such unsolvable levels and check whether current level is in that collection. If it is found to be there then it is reported (with red status) that level is in unsolvable collection. (This feature was requested by Ming)

YSokoban can not check whether some level is unsolvable. It simply believes user. If he says level is unsolvable then this level is preserved in unsolvable collection. Of course if level was already solved and is in a data file of a player, then it is not marked as unsolvable. Trivial levels are also not marked as unsolvable.

Unsolvable levels are kept in a file unsolvable in YSokoban folder. This file is same format as .sokoinfo files and keeps levels in normalized form.

If you want to clear unsolvable collection - remove file "unsolvable" from YSokoban folder.

## Methods to mark level as unsolvable

No level is put automatically in unsolvable, this shall be done explicitly.

## Import unsolvable - import text file with unsolvable levels

Use "Import unsolvable" to import new levels in unsolvable collection. This is shall be a file with levels you get from somewhere and is believed that it contains only unsolvable levels. During import levels are checked and if a solution for some of them is found then that level is not imported in unsolvable.

## Export unsolvable - export text file with unsolvable levels

Use "Export unsolvable" to export all unsolvable levels (in normalized form). You can share this text files with other people.

## Add current level to unsolvable

Simply select this from menu and current level (which you are currently playing) will be marked as unsolvable (put into unsolvable file). You can not mark it as unsolvable if it already has solutions.

## Remove current level from unsolvable

If level is reported as unsolvable (you will see this in bottom right corner where solution is present) then it is possible to remove it from unsolvable (because somebody to whom you believe says it is solvable or because of any other reason). Select this from menu and level will be removed. Level will be removed from unsolvable if you solve it (or paste a solution).

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