advanced crossword construction tool

 Qxw is a program to help you create and publish crosswords,
 from the simplest blocked grid to sophisticated thematic
 puzzles. It can make rectangular-, hexagonal- or
 circular-format grids with blocks, bars or both. It
 has an automatic grid-filling facility that can handle a
 wide range of answer treatments and you can even add your
 own answer treatment methods. Grids can be filled using
 letters, digits, or a mixture of both; non-Roman and
 custom alphabets are also supported. Qxw can produce
 output in a range of formats ready for publication.
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 Qxw also has a non-interactive mode that can solve a wide
 range of word-based constraint satisfaction problems and
 can help automate the exploration of grid designs.
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 Qxw is written in C and has a GUI based on GTK+.