Comment by gus_massa

> is it possible to create a board that has multiple valid solutions?

Some simple boards like

  11111111
  22222222
  33333333
  44444444
  55555555
  66666666
  77777777
  88888888

or

  11112222
  11112222
  33334444
  33334444
  55556666
  55556666
  77778888
  77778888

have many solutions.