public GameObject[] tilePrefabs;
private float spawnZ = -19.0f;
private float tileLength = 24.0f;
private List<GameObject> activeTiles;

private void DeleteTile()
    {
        //Destroy(activeTiles[0]);
        activeTiles[0].SetActive(false);
        activeTiles.RemoveAt(0);
    }

    private void SpawnTile(int prefabIndx = -1)
    {
        GameObject go;
        if (prefabIndx == -1)
        {
            go = Instantiate(tilePrefabs[RandomPrefabIndex()])as GameObject;
            go.SetActive(false);

        }
        else
        {
            go = Instantiate(tilePrefabs[prefabIndx]) as GameObject;
            go.SetActive(false);
        }

        go.transform.SetParent(transform);
        go.transform.position = Vector3.forward * spawnZ;
        spawnZ += tileLength;
        //activeTiles.Add(go);
        go.SetActive(true);
        activeTiles.Add(go);
    }