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

 ItemObject_Trigger.cs

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

public class ItemObject_Trigger : MonoBehaviour
{
    private ItemObject myItemObject => GetComponentInParent<ItemObject>();
    private void OnTriggerEnter2D(Collider2D collision)
    {
        if (collision.GetComponent<Player>() != null)
        {
            myItemObject.PickupItem();
        }
    }
}

ItemObject.cs

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

public class ItemObject : MonoBehaviour
{
    private SpriteRenderer sr;

    [SerializeField] private Rigidbody2D rb;//设置速度
    [SerializeField] private ItemData ItemData;
    [SerializeField] private Vector2 velocity;//设置速度


    private void SetupVisuals()
    {
        if (ItemData == null)
            return;

        GetComponent<SpriteRenderer>().sprite = ItemData.icon;
        gameObject.name = ItemData.name;
    }
   
    public void SetupItem(ItemData _itemData,Vector2 _velocity)设置实例函数
    {
        ItemData = _itemData;
        rb.velocity = _velocity;//设置速度

        SetupVisuals();
    }

    public void PickupItem()//拾取函数打包
    {
        Inventory.instance.AddItem(ItemData);
        Destroy(gameObject);
    }
}

ItemDrop.cs

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

public class ItemDrop : MonoBehaviour
{
    [SerializeField] private int possibleItemDrop;//设置可能会出现的材料数量
    [SerializeField] private ItemData[] possibleDrop;
    
    private List<ItemData> dropList = new List<ItemData>();

    [SerializeField] private GameObject dropPrefab;
    [SerializeField] private ItemData item;

    public void GenerateDrop()//随机生成物品函数
    {
        for(int i = 0;i<possibleDrop.Length;i++)//一个判断可能出现的装备
        {
            if(Random.Range(0,100) <= possibleDrop[i].dropChance)
            {
                dropList.Add(possibleDrop[i]);
            }       
        }
        for (int i = 0; i < possibleItemDrop; i++)//另一个生成可能出现的装备
        {
            ItemData randomItem = dropList[Random.Range(0, dropList.Count - 1)];
            if(possibleItemDrop <= dropList.Count )
            {
                dropList.Remove(randomItem);
            }
           
            DropItem(randomItem);
        }
    }

    public void DropItem(ItemData _itemData)//创建实例函数
    {
        GameObject newDrop = Instantiate(dropPrefab, transform.position,Quaternion.identity);

        Vector2 randomVelocity = new Vector2(Random.Range(-5, 5), Random.Range(15, 20));

        newDrop.GetComponent<ItemObject>().SetupItem(_itemData, randomVelocity);
    }
}

 EnemyStats.cs

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

public class EnemyStat : CharacterStats
{
    private Enemy enemy;
    private ItemDrop myDropSystem;

    [Header("Level details")]
    [SerializeField] private int leval = 1;

    [Range(0f, 1f)]//一个使数值设置成为一定范围的设置
    [SerializeField] private float percantageModifier = .4f;//设置等级和成长比例

    public override void DoDamage(CharacterStats _targetStats)
    {
        base.DoDamage(_targetStats);
    }

    protected override void Die()
    {
        base.Die();
        enemy.Die();

        myDropSystem.GenerateDrop();
    }

    protected override void Start()
    {
        //改变伤害和生命值
        //解决初始血量在升级后不满
        ApplyLevelModifier();

        enemy = GetComponent<Enemy>();
        base.Start();

        myDropSystem = GetComponent<ItemDrop>();

    }

    private void ApplyLevelModifier()
    {
        Modify(strength);
        Modify(agility);
        Modify(intelligence);
        Modify(vitality);

        Modify(damage);
        Modify(critChance);
        Modify(critPower);

        Modify(maxHealth);
        Modify(armor);
        Modify(evasion);
        Modify(magicResistance);

        Modify(fireDamage);
        Modify(iceDamage);
        Modify(lightingDamage);
    }

    //专门对某个数值进行提升的函数
    private void Modify(Stat _stat)
    {
        for(int i =1;i<leval;i++)
        {
            float modifier = _stat.GetValue() * percantageModifier;

            _stat.AddModifier(Mathf.RoundToInt(modifier));
        }
    }

    public override void TakeDamage(int _damage)
    {
        base.TakeDamage(_damage);

    }
}

ItemData.cs

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

public enum ItemType
{
    Material,
    Equipment
}

[CreateAssetMenu(fileName = "New Item Data", menuName = "Data/Item")]
public class ItemData : ScriptableObject 
{
    public ItemType itemType;
    public string itemName;
    public Sprite icon;//图标

    [Range(0,100)]
    public float dropChance;
}