private IEnumerator UpdateCoolingDown(Spell spell)
{
float cd = 0;
float rev = 360f * spell.cooldown_time; // one revolution for each second of cooldown
while (true)
{
cd = Mathf.Pow(1 - spell.GetCooldownPercent(), 2);
transform.rotation = Quaternion.Euler(0, 0, cd*rev);
if (!spell.IsOnCooldown()) break;
yield return null;
}
icon.enabled = false;
}