docs: function getPreviousStep(that) {
          var curStage,  prevStage;
          curStage = node.game.getCurrentGameStage();
          if (curStage.stage === 0) return;
          prevStage = node.game.getPreviousStep();
          if (prevStage.stage === 0) return;
          if ((curStage.stage > prevStage.stage) && !that.acrossStages) {
              return false;
          }
          if ((curStage.round > prevStage.round) && !that.acrossRounds) {
              return false;
          }
          return prevStage;
      }