MountainSpawner

    public GameObject mountains;

    public float mountainSpawnRateMax;
    public float mountainSpawnRateMin;

    public float maxZ;
    public float minZ;

    public float maxScalex;
    public float minScalex;

    public float maxScaley;
    public float minScaley;

    public float mountainSpeed;

    bool t;

    void OnEnable()
    {
        Rigidbody2D[] m = GetComponentsInChildren<Rigidbody2D>();
        foreach (Rigidbody2D mnt in m)
        {
            mnt.velocity = new Vector3(-1 * mountainSpeed, 0, 0);
        }
        t = true;
        Invoke("SpawnMountain", Random.Range(mountainSpawnRateMin, mountainSpawnRateMax));
    }

    void OnDisable()
    {
        t = false;
    }

    void SpawnMountain()
    {
        float ranZ = Random.Range(minZ, maxZ);
        Vector3 spawnPos = new Vector3(transform.position.x, transform.position.y, transform.position.z + ranZ);
        GameObject mountain = Instantiate(mountains, spawnPos, Quaternion.identity) as GameObject;
        mountain.GetComponent<Rigidbody2D>().velocity = new Vector3(-1 * mountainSpeed, 0, 0);
        mountain.transform.parent = transform;
        float ranScalex = Random.Range(minScalex, maxScalex);
        float ranScaley = Random.Range(minScaley, maxScaley);
        mountain.transform.localScale -= new Vector3(ranScalex, ranScaley, 0);
        if(t == true)
        {
            Invoke("SpawnMountain", Random.Range(mountainSpawnRateMin, mountainSpawnRateMax));
        }
    }