Ouch is not really the best word to use when the game is over. If the score is probably 500 or less, ouch makes sense. If you have a much better score, not so much.
You may wish to try different messages depending on the score level, if that is possible. Such as: great job, or, better luck next time, or keep going, or try again, or oops you're out of moves on this one...
Probably a good idea to encourage versus discourage your players.