Command line parameters:
  -v       Verbose mode.  Print out solution steps.
  -o file  Output the solution to file.
  -f file  Read puzzle from file.
  -s       Try to solve the puzzle non-interactively.


Keys:
  WSAD   Move the cursor around
  Space  Try to solve he puzzle
  T      Single solution step
  1-9    Set a cell
  0      Clear a cell
  ?+1-9  (Question mark, then number) Highlight candidates for the given number
  ?+0    Clear highlight
  X      Toggle expanded mode
  E      Eliminate candidates
  Q      Quit
  F      Fix current cells
  C      Clear non-fixed cells
