void SwapTiles(int x1, int y1, int x2, int y2)
{
Tile tile1 = repository.Get(x1, y1);
Tile tile2 = repository.Get(x2, y2);
int aux = tile1.Number;
tile1.Number = tile2.Number;
tile2.Number = aux;
repository.Update(tile1);
repository.Update(tile2);
}
