title: A good randomizer for puzzle-15
body: <p>I have implemented a puzzle 15 for people to compete online. My current randomizer works by starting from the good configuration and moving tiles around for 100 moves (arbitrary number)</p>
  
  <p>Everything is fine, however, once in a little while the tiles are shuffled too easy and it takes only a few moves to solve the puzzle, therefore the game is really unfair for some people reaching better scores in a much higher speed.</p>
  
  <p>What would be a good way to randomize the initial configuration so it is not "too easy"? </p>