anchor.diff:      return liveStates.fold(0, (sum, live) => sum + (live ? 1 : 0));
     }
   
  -  List<List<Cell>> generateRandomGrid(seed) {
  +  List<List<Cell>> generateRandomGrid(int seed) {
       var rnd = new Random(seed);
       return new List<List<Cell>>.generate(numRows,
           (int rowIdx) => new List<Cell>.generate(numCols,
  
positive.code:     switchGrids();
    }
  
    Cell getCell(g, x, y) {
      return g[y][x];
    }
  
    int numNeighbours(List<List<Cell>> g, x, y) {
      var left = x-1;
      var right = x+1;
      var above = y-1;
  
negative.code:     var timer = new Timer.periodic(new Duration(milliseconds: 100), updateCells);
    }
  
    updateCells(Timer timer) {
      if (paused)
        return;
  
  