docs: function() {
          if (this.grid) {
              for(var iRow=0, len=this.grid.length; iRow<len; iRow++) {
                  var row = this.grid[iRow];
                  for(var iCol=0, clen=row.length; iCol<clen; iCol++) {
                      var tile = row[iCol];
                      this.destroyTile(tile);
                  }
              }
              this.grid = [];
              this.gridResolution = null;
              this.gridLayout = null;
          }
      }