一，使用velocity方法移動角色；

二，使用localScale，使x等於負數實現圖片反轉；

三，m_rg.velocity = 數值*方向；

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

public class PlayerController : MonoBehaviour {

    private Rigidbody2D m_rg;

    public float MoveSpeed;


    void Start () {

        m_rg 
 
= gameObject.GetComponent<Rigidbody2D>();

    }
    
    // Update is called once per frame
    void Update () {
        //------------------Input.GetAxisRaw沒有小數值，只有整數，不會產生緩動------------------
        //角色水平移動
        //按住D鍵，判斷如果大於0，則向右開始移動
        if (Input.GetAxisRaw("Horizontal") > 0)
        {
            m_rg.velocity 
 
= new Vector2(MoveSpeed, m_rg.velocity.y);

            //設定自身縮放的值
            transform.localScale = new Vector2(1f,1f);
        }
        //角色水平移動
        //按住A鍵，判斷如果小於0，則向左開始移動
        else if (Input.GetAxisRaw("Horizontal") < 0)
        {
            m_rg.velocity = new Vector2(-MoveSpeed, m_rg.velocity.y);

            
 
//如果new Vector2(-1f, 1f)  x值為負數，則圖片進行反轉顯示
            transform.localScale = new Vector2(-1f, 1f);
        }
        else
        //角色水平移動
        //鬆開按鍵，判斷如果等於0，則停止移動
        {
            m_rg.velocity = new Vector2(0, m_rg.velocity.y);
        }

    }
}