Alex教程每一P的教程原代码加上我自己的理解初步理解写的注释，可供学习Alex教程的人参考
此代码仅为较上一P有所改变的代码
【Unity教程】从0编程制作类银河恶魔城游戏_哔哩哔哩_bilibili

Sword_Skill_Controller.cs

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

public class Sword_Skill_Controller : MonoBehaviour
{
    [SerializeField] private float returnSpeed = 12;
    private bool isReturning;

    private Animator anim;
    private Rigidbody2D rb;
    private CircleCollider2D cd;
    private Player player;

    private bool canRotate = true;

    public float bounceSpeed;//设置弹跳速度
    public bool isBouncing = true;//判断是否可以弹跳
    public int amountOfBounce = 4;//弹跳的次数
    public List<Transform> enemyTargets;//保存所有在剑范围内的敌人的列表
    private int targetIndex;//设置targetIndex作为敌人计数器

    private void Awake()
    {
        anim = GetComponentInChildren<Animator>();
        rb = GetComponent<Rigidbody2D>();
        cd = GetComponent<CircleCollider2D>();
    }
    public void ReturnSword()
    {
        rb.constraints = RigidbodyConstraints2D.FreezeAll;//修复剑只要不触碰到物体就无法收回的bug
        //rb.isKinematic = false;
        transform.parent = null;
        isReturning = true;
    }
    public void SetupSword(Vector2 _dir,float _gravityScale,Player _player)
    {
        player = _player;
        rb.velocity = _dir;
        rb.gravityScale = _gravityScale;
        anim.SetBool("Rotation", true);
    }

    private void Update()
    {
        if(canRotate)
        transform.right = rb.velocity;//使武器随着速度而改变朝向

        if (isReturning)
        {
            transform.position = Vector2.MoveTowards(transform.position, player.transform.position, returnSpeed * Time.deltaTime);//从原来的位置返回到player的位置
                                                                                                                                 //并且随着时间增加而增加速度
            if(Vector2.Distance(transform.position,player.transform.position)<1)//当剑与player的距离小于一定距离，清除剑
            {
                player.CatchTheSword();
            }
        }                
        
        if(isBouncing && enemyTargets.Count > 0)
        {
            
            transform.position = Vector2.MoveTowards(transform.position, enemyTargets[targetIndex].position,bounceSpeed*Time.deltaTime);
            //3.当可以弹跳且列表内数量大于0，调用ToWords,这将使剑能够跳到敌人身上
            if (Vector2.Distance(transform.position, enemyTargets[targetIndex].position)<.1f)
            {
                targetIndex++;
                amountOfBounce--;//设置弹跳次数
                if (amountOfBounce <= 0)
                {
                    isBouncing = false;
                    isReturning = true;
                }//这样会使当弹跳次数为0时，返回到角色手中
                if (targetIndex >= enemyTargets.Count)
                {
                    targetIndex = 0;
                }
            }//利用与目标距离的判断，使剑接近目标距离时切换到下一个目标。
                 //且如果所有目标都跳完了，切回第一个
        }
    }

  
    private void OnTriggerEnter2D(Collider2D collision)//传入碰到的物体的碰撞器
    {
        if (isReturning)
        {
            return;
        }//修复在返回时扔出时没有碰到任何物体，但返回时碰到了物体导致剑的一些性质发生改变的问题，及回来的时候调用了OnTriggerEnter2D

        if (collision.GetComponent<Enemy>() != null)//首先得碰到敌人，只有碰到敌人才会跳
        {
            if (isBouncing && enemyTargets.Count <= 0)
            {
                Collider2D[] colliders = Physics2D.OverlapCircleAll(transform.position, 10);
                foreach (var hit in colliders)
                {
                    if (hit.GetComponent<Enemy>() != null)
                    {
                        enemyTargets.Add(hit.transform);
                    }
                }
            }
        }

        StuckInto(collision);
    }//打开IsTrigger时才可使用该函数
    //https://docs.unity3d.com/cn/current/ScriptReference/Collider2D.OnTriggerEnter2D.html

    private void StuckInto(Collider2D collision)
    {
        canRotate = false;
        cd.enabled = false;//相当于关闭碰撞后触发函数。//https://docs.unity3d.com/cn/current/ScriptReference/Collision2D-enabled.html

        rb.isKinematic = true;//开启物理学反应 https://docs.unity3d.com/cn/current/ScriptReference/Rigidbody2D-isKinematic.html
        rb.constraints = RigidbodyConstraints2D.FreezeAll;//冻结所有移动

        if (isBouncing&&enemyTargets.Count>0)//修复剑卡不到墙上的bug
            return;
        //终止对动画的改变和终止附在敌人上
        transform.parent = collision.transform;//设置sword的父组件为碰撞到的物体
        anim.SetBool("Rotation", false);
    }
    
}