This version of the spaceship script works in Unity 2018

I had problems making the spaceship script work (haven't tried the bullet script yet). Here are the changes I've done to the script to make it work for me in Unity 2018 :

- the rigidbody2D.AddForce()... line is not working in Unity 2018. I've changed this line and added 2 other lines (look for them in the vicinity of the void Start() line)
-  my spaceship was jumping to one corner of the screen just after the start of the game. The reason was the values for screenSW and screenNE were inverted so I changed the lines were they get their values and it fixed the problem.  EDIT : no need to do this change, problem was my camera was not set properly, it needs to be set to 'orthographic'

Here's the whole script.

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using UnityEngine;

using System.Collections;

using System.Collections.Generic;

public class Spaceship : MonoBehaviour {

    public GameObject spaceshipBulletPrefab;

    public float speed =  1f;

    public float turnSpeed = 1f;

    public float fireRate = 0.5f;

    private float accelRate = 0f;

    private Animator animator;

    private Vector3 screenSW;

    private Vector3 screenNE;

    private float wrapPadding = 1f;

    private bool hit = false;

    private float nextFire;

   public Rigidbody2D rb2D;

   // Use this for initialization

   void Start () {

        animator = GetComponent<Animator>();

       rb2D = GetComponent<Rigidbody2D>();

       screenNE = Camera.main.ScreenToWorldPoint(new Vector3(0, 0, Camera.main.transform.localPosition.z));

       screenSW = Camera.main.ScreenToWorldPoint(new Vector3(Screen.width, Screen.height, Camera.main.transform.localPosition.z));

   }

    // Update is called once per frame

    void Update () {

        float translation = Input.GetAxis("Vertical");

        float rotation = Input.GetAxis("Horizontal");

        if(rotation > 0){

            TurnRight(rotation);

        }

        else if(rotation < 0){

            TurnLeft(rotation);

        }

        if(translation >= 0.5f){

            Move(translation);

        }

        else{

            Idle();

        }

        if(Input.GetButton("Jump")){

            ShootBullet();

        }

       rb2D.AddForce(transform.up * (speed * accelRate));

       if (transform.localPosition.x < screenSW.x - wrapPadding){

            transform.localPosition = new Vector3(screenNE.x, transform.localPosition.y, transform.localPosition.z);

        }

        else if(transform.localPosition.x > screenNE.x + wrapPadding){

            transform.localPosition = new Vector3(screenSW.x, transform.localPosition.y, transform.localPosition.z);

        }

        if(transform.localPosition.y < screenSW.y - wrapPadding){

            transform.localPosition = new Vector3(transform.localPosition.x, screenNE.y, transform.localPosition.z);

        }

        else if(transform.localPosition.y > screenNE.y + wrapPadding){

            transform.localPosition = new Vector3(transform.localPosition.x, screenSW.y, transform.localPosition.z);

        }

    }

    public void TurnRight(float rotation = 1){

        if(hit){

            return;

        }

        transform.Rotate(Vector3.back * (rotation * turnSpeed));

    }

    public void TurnLeft(float rotation = 1){

        if(hit){

            return;

        }

        transform.Rotate(Vector3.forward * (rotation * -turnSpeed));

    }

    public void Move(float accel){

        if(hit){

            return;

        }

        accelRate = accel;

        animator.SetInteger("State", 1);

    }

    public void Idle(){

        if(hit){

            return;

        }

        accelRate = accelRate * 0.5f;

        animator.SetInteger("State", 0);

    }

    public void ShootBullet(){

        if(hit){

            return;

        }

        if(Time.time > nextFire){

            nextFire = Time.time + fireRate;

            Instantiate(spaceshipBulletPrefab, transform.localPosition, transform.localRotation);

        }

    }

}