public void OnCompleteChallenge()
{
foreach (PunchScaleUp punch in FindObjectsOfType <PunchScaleUp>())
{
Destroy(punch.gameObject);
}
bus.gameObject.SetActive(true);
bus.Resume();
// resume spawning
Invoke(nameof(SpawnChallenge), Random.Range(spawnRate.x, spawnRate.y));
}