Reconfigure Jame's Knight Game to have the ability to manage state

gistfile1.js

(function () {
  var save;
  var freshBoard;

  var oldSetupGame = this.setupGame;
  this.setupGame = function() {
    oldSetupGame();
    save = freshBoard = saveState();
  }

  var saveState = function() {
    return {
      visited: $$('.visited'),
      current: $('knight').parentNode
    }
  }

  var restoreState = function(state) {
    if (!state) return;

    var knight = $('knight');
    $$('.visited').each(function(cell){ cell.removeClassName('visited'); cell.addClassName('unvisited')})
    state['visited'].each(function(cell) { cell.addClassName('visited') });
    state['current'].appendChild(knight);
    LEGAL_MOVES.each(function(item) { $(item).stopObserving('click'); });
    setHandlerForLegalMoves(knight.parentNode)
  }

  $('board').insert('<input type="button" value="Re-Generate" id="regenerate" />');
  $('board').insert('<input type="button" value="Restart" id="restart" />');
  $('board').insert('<input type="button" value="Load" id="load" />');
  $('board').insert('<input type="button" value="Save" id="save" />');

  $('regenerate').observe('click', setupGame);
  $('restart').observe('click', function() {restoreState(freshBoard)});
  $('save').observe('click', function() {save = saveState()});
  $('load').observe('click', function() {restoreState(save)});

  setupGame();
}).call(this);