BulletBehavior

using UnityEngine;
using System.Collections;

public class BulletBehavior : MonoBehaviour {

	private float speed = 5f;
	public float rotationSpeed;
	private Transform myTrans;
	private Vector3 myPos, myRot;
	private float angle;

	void Start (){
		myTrans = transform;
		myPos = myTrans.position;
		myRot = myTrans.rotation.eulerAngles;
	}

	void FixedUpdate () {

		angle = myTrans.eulerAngles.magnitude * Mathf.Deg2Rad;

		if (Input.GetKey (KeyCode.RightArrow)) {
			myRot.z -= rotationSpeed;
		}
		if (Input.GetKey (KeyCode.LeftArrow)) {
			myRot.z += rotationSpeed;
		}

		if (Input.GetKey (KeyCode.UpArrow)) {

			myPos.x += (Mathf.Cos (angle) * speed) * Time.deltaTime;
			myPos.y += (Mathf.Sin (angle) * speed) * Time.deltaTime;
		}

		if (Input.GetKey (KeyCode.DownArrow)) {
			myPos.x += Mathf.Cos (angle) * Time.deltaTime;
			myPos.y += Mathf.Sin (angle) * Time.deltaTime;
		}

		myTrans.position = myPos;
		myTrans.rotation = Quaternion.Euler (myRot);

	}
}