Unity+C# simple missile

using UnityEngine;
using System.Collections;

public class SimpleSteering : MonoBehaviour
{
    Rigidbody2D rb2D;
    //Target we want to hit. Rigidbody2D because we can hit if it's moving.
    //Needs to be set or object will fly into nowhere.
    public Rigidbody2D target;
    //Force multiplier. We multiply force with magnitude of 1(normalized) to this.
    public float forcePower = 20f;
    //Limit of speed. See its comment in FixedUpdate().
    public float speedLimit = 5f;
    void Start()
    {
        rb2D = GetComponent<Rigidbody2D>();
        //Random speed at start.
        rb2D.velocity = new Vector2(Random.Range(-speedLimit, speedLimit), Random.Range(-speedLimit, speedLimit));
    }
    //Measures distance in clockwise and counterclockwise directions between angles in radians and returns smallest
    float ShortestAngleBetween(float anglestart, float anglefinish)
    {
        float counterClockwiseDistance, clockwiseDistance;//Counterclockwise
        if (anglefinish < anglestart)
        {
            clockwiseDistance = anglestart - anglefinish;
            counterClockwiseDistance = Mathf.PI * 2 - anglestart + anglefinish;
        }
        else {
            clockwiseDistance = Mathf.PI * 2 - anglefinish + anglestart;
            counterClockwiseDistance = anglefinish - anglestart;
        }
        if (counterClockwiseDistance < clockwiseDistance) return counterClockwiseDistance;
        else return -clockwiseDistance;
    }
    //Checks angle in radians between vectors. Positive is counterClockwise, negative is clockwise.
    float AngleBetweenVectors(Vector2 first, Vector2 second)
    {
        float ang1 = Mathf.Atan2(first.y, first.x), ang2 = Mathf.Atan2(second.y, second.x);
        return ShortestAngleBetween(ang1, ang2);
    }
    void FixedUpdate()
    {
        Vector2 targetPosition;
        //Target position with preemtion so that we can hit if it isn't stationary.
        if (rb2D.velocity.magnitude > 0.0001f)
            targetPosition = (target.position + target.velocity * (rb2D.position - target.position).magnitude / rb2D.velocity.magnitude);
        else//Division by zero case
            targetPosition = target.position;
        //Direction we want to fly
        Vector2 direction = targetPosition - rb2D.position;
        //Angle difference coefficient 30 here can be modified. Smaller means we rotate to needed angle aggressively
        float angleChangeMagnitude = AngleBetweenVectors(direction, rb2D.velocity) * Mathf.Rad2Deg / 30;
        //Force basis.
        Vector2 resultingForce = new Vector2(angleChangeMagnitude, 1);
        //We take force basis, normalize it and multiply by power.
        rb2D.AddRelativeForce(forcePower * resultingForce.normalized);
        //Rotate the object itself to face where it flies. -90 because we fly to Y, not X.
        rb2D.rotation = Mathf.Rad2Deg * Mathf.Atan2(rb2D.velocity.y, rb2D.velocity.x) - 90;
        //Speed limit. Without it, we will often miss as missile will go spiral and, won't have enough side force to rotate properly.
        //Can be solved by multiplying side force (angleChangeMagnitude) by value that depends on rb2D.velocity.magnitude.
        if (rb2D.velocity.magnitude > speedLimit)
            rb2D.velocity = rb2D.velocity.normalized * speedLimit;
    }
    //Note: for simplicity, collisions don't check if we hit another missile. That doesn't affect result much.
    public void OnCollisionEnter2D(Collision2D collision)//In case we don't use trigger collider
    {
        Debug.Log("Hit");
        Destroy(gameObject);
    }
    public void OnTriggerEnter2D(Collider2D collision)//In case we use trigger collider
    {
        Debug.Log("Hit");
        Destroy(gameObject);
    }
}