To demonstrate the game, I've provided thirty levels in three sets of graded difficulty. The links take you to the first of each set. Use your arrow keys to move the player token (@ or +) and push the boxes ($ or *) around and into the goals (.). There is no undo, so if you make a mistake, just hit Refresh (F5 on most browsers) to restart the level. Once you've solved the first level of the set, a link will appear for the second level of the set, and so on and so forth to the tenth level of the set.
All levels are by Alonso del Arte unless otherwise indicated.
I've also created Illustrative Levels, which are not easy or difficult per se, but are more intended to illustrate certain aspects of the game.
And there's also two template levels, Template Level A and Template Level B, for those of you interested in making your own ASCII Sokoban levels (those should both give a warning that the number of boxes does not match the number of goals).
Maybe someone will add a level creator tool (I have a placeholder for that) and a solution verifier (I also have a placeholder for that).