My bullet changes the velocity depending on where I click

Question

I want to build a little 2D-Sidescrolling shooter and I'm now at the shooting script.

I already figured out how to shoot a bullet towards my mouse pointer. I got something like this :

Vector3 shootDirection;
        shootDirection = Input.mousePosition;
        shootDirection.z = 0.0f;
        shootDirection = Camera.main.ScreenToWorldPoint (shootDirection);
        shootDirection = shootDirection - transform.position;

        shootDirection.Normalize ();

        Rigidbody2D bulletInstance = Instantiate (rocket, transform.position, Quaternion.identity) as Rigidbody2D;
        bulletInstance.velocity = new Vector2 (shootDirection.x * speed, shootDirection.y * speed);

Now obviously the bullet goes faster if my Direction coordinates are big and slower if they are smaller. Have you some better code for me or how can I fix that issue?

I added now some loop like this, which brings a horrible performance, but kinda works out for the problem, but I'm still looking for a better solution.

while (((shootDirection.x * speed) + (shootDirection.y * speed)) < 20) {
            speed += 0.1f;
        }

So the loop makes sure that the overall speed is always almost the same, but this solution ends in an infinity loop if the values get too small.

Answer 1

Actually the 2D-Vector solved the problem, I don't know why, because I think it should do the same but this is my code now and it's working

        Vector2 target = Camera.main.ScreenToWorldPoint (new Vector2 (Input.mousePosition.x, Input.mousePosition.y));
        Vector2 myPos = new Vector2 (transform.position.x, transform.position.y);
        Vector2 direction = target - myPos;
        direction.Normalize ();
        Rigidbody2D projectile = Instantiate (rocket, myPos, Quaternion.identity) as Rigidbody2D;
        projectile.velocity = direction * speed;