//放置灰色格子
public void PlaceGreyCell(Vector2Int pos)
{
GameObject grid = Instantiate(VirusGreyPrefab);
grid.transform.parent = GridRoot.transform;
grid.transform.localPosition = perUnitScale * (Vector2)pos;
grid.transform.localScale *= perUnitScale;
grid.GetComponent <Cell> ().SetIndex(pos.x, pos.y);
GreyCells.Add(grid.GetComponent <Cell> ());
virusCount++;
}