(Note: Charles Forsythe's authorship was confirmed via email by gamingafter40.)
A C64 BASIC version was published as a type-in game in the book Castles & Kingdoms. The game is slightly different to the TRS80 version. North/South and East/West have been switched, and one or two of the objects are different. Many versions on the Internet have typo's making the game unsolvable. Simon's fixed version (below) addresses many of these and also includes the magic word omitted from the book.
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