Sokoban was invented in 1980 by Hiroyuki Imabayashi, and first published by Thinking Rabbit. The name comes from the Japanese for 'warehouse keeper' (倉庫番).
The idea of the game is simple. The board represents a warehouse. Scattered around the floor of the warehouse are a number of boxes, represented by blue circles. The warehouse keeper is represented by a red circle. Your job is to direct the warehouse keeper to move the boxes to the special, dark squares. The only rules are that the warehouse keeper can only push a box, not pull it, and only one box can be pushed at a time.
To move a box first click on it. Its background will be highlighted. Then click on the square to which the warehouse keeper should move the box. If the move cannot be performed an audible beep will be heard. There are 3 reasons for not being able to move the box:
There is no open square directly behind the box in the direction required to push it (the push square).
The warehouse keeper cannot be moved to the push square.
The box cannot be pushed to the target square because something is blocking the way or because the target square is not in one of the cardinal directions from the box.
If you decide that you do not want to move a selected box click it again and it will be unselected. There is an 'Undo' button to rewind your moves if you decide you have gone down the wrong path.
The game has 2 collections of warehouse layouts. Each collection has 50 layouts to try. Select the collection and the layout you would like to play and then click 'Start Game'. The 'Original' collection of layouts are based on those that were published with the original Thinking Rabbit game. The other collection is based on one called 'Sasquatch' that was created by David Skinner. That collection, while somewhat more difficult than the 'Original' collection has been described as 'just the right difficulty to be fun: not too easy, but (usually) not so hard that you get frustrated'.