private void CopyGrid(Playfield playfield)
 {
     for (int row = 0; row < this.size; row++)
     {
         for (int col = 0; col < this.size; col++)
         {
             this.grid[row, col] = playfield.GetCell(row, col);
         }
     }
 }
 public GameEngine(IReader reader, IRenderer renderer, Playfield playfield)
 {
     this.reader = reader;
     this.renderer = renderer;
     this.playfield = playfield;
 }
 /// <summary>
 /// Set size, and copy grid from passed playfield
 /// </summary>
 /// <param name="playfield"></param>
 public Memento(Playfield playfield)
 {
     this.size = playfield.Size;
     this.grid = new string[this.size, this.size];
     this.CopyGrid(playfield);
 }