private void PerformAdd()
{
if (obj is EnemyInstance)
{
if (insertIndex == -1)
{
insertIndex = Screen.Enemies.Count;
}
Screen.AddEnemy((EnemyInstance)obj, insertIndex);
}
else if (obj is StructInstance)
{
if (insertIndex == -1)
{
insertIndex = Screen.Structs.Count;
}
Screen.AddObject((StructInstance)obj, insertIndex);
}
}