使刚体2d向后移动

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Fighter_movement : MonoBehaviour
{

    public float thrust;
    public float drag;
    public Rigidbody2D rb;

    // Use this for initialization
    void Start()
    {
        rb = GetComponent<Rigidbody2D>();
    }

    // Update is called once per frame
    void FixedUpdate()
    {
        float moveHorizontal = Input.GetAxis("Horizontal");
        float moveVertical = Input.GetAxis("Vertical");

        Vector2 movement = new Vector2(moveHorizontal, moveVertical);

        rb.AddForce(movement);

    }
}