Continue Later and/or Quit Button(s)
Could you add a CONTINUE Later and/or QUIT button ?
I have had to leave the game and/or sign off my machine, once even reboot in the middle of the game.
I would have loved to come back later and complete it later. Now it just says I have failed to solve it which to me is a bummer. I didn't fail - I just didn't get to finish.
If someone doesn't think they can solve the puzzle then a QUIT or SURRENDER button would give them the answers. If that button is not pushed then the game would not be over.
I love logic puzzles always have but don't always have time to complete in one sitting. Other things come up with higher priorities.