P2D4

Made player and enemies into a trigger; gave them "enemy" tag;  the projectile now destroys up to 2 enemies.

void OnTriggerEnter2D(Collider2D coll)
    {
        Debug.Log ("collided with" + coll.gameObject.name);
        if (coll.gameObject.tag == "enemy")
        {
            Destroy (coll.gameObject);
            gameControl addScore = GetComponent<gameControl>();
            addScore.scoring ();
            hitNum += 1;
        }
        if (hitNum >= 2)
        {
            DestroyObject(this.gameObject);
        }
    }
problem? addScore.scoring isn't working :(

gameControl.cs function below:

    public void scoring ()
    {
        Debug.Log ("scoring is being called");
        playerScore += 1;
    }

Error, on the addScore.scoring(); line:

NullReferenceException: Object reference not set to an instance of an object
projectile_sc.OnTriggerEnter2D (UnityEngine.Collider2D coll) (at Assets/projectile_sc.cs:36)

Note:
Have the ranged minions walk around the edge of arena, shooting at the player.  Maybe put in obstacles for player to hide behind.

Update:
Made score a static variable and scoring a static function.
A static function can be called without an object reference.
 Scoring, in gameControl script:
     public static void scoring ()
    {
        playerScore += 1;
        Debug.Log (playerScore);
    }
 Calling it from another script:

            gameControl.scoring ();


Had a Singleton tutorial from herbie.
It's essentially a static public class that creates an instance of itself when called, so other scripts can access the non-static functions attached to it.  Should only be used when there is only 1 of it, like in scoring.

public class scores : MonoBehaviour {
    protected static scores m_instance = null;
    protected int m_currentScore = 0;

    // Use this for initialization
    void Start () {
   
    }
   
    // Update is called once per frame
    void Update () {
   
    }

    public static scores instance ()
    {
        if ((m_instance) == null)
        {
            m_instance = new GameObject("scoresSingleton").AddComponent<scores>();
        }
        return m_instance;
    }

    public void increaseScore()
    {
        m_currentScore++;
        Debug.Log (m_currentScore);
    }
}

GetComponent only works on things attached to current object.
FindComponentbyType/Name are slower functions and I should avoid using these in updates.
When using either, store the results in an variable and just use those.

Use the "xxx = null" "if xxx = null, xxx = return value" to make sure xxx only gets defined once.