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

UI.cs

using UnityEngine;

public class UI : MonoBehaviour
{
    [SerializeField] private GameObject characterUI;
    [SerializeField] private GameObject skillTreeUI;
    [SerializeField] private GameObject craftUI;
    [SerializeField] private GameObject optionsUI;

    public UI_itemTooltip itemToolTip;
    public UI_statToolTip statToopTip;
    public Ui_SkillToolTip skillToolTip;

    public UI_CraftWindow craftWindow;
    public void Start()
    {
        SwitchTo(null);
        itemToolTip.gameObject.SetActive(false);
        statToopTip.gameObject.SetActive(false);
    }

    private void Update()
    {
        if(Input.GetKeyDown(KeyCode.C))
        {
            SwitchWithKeyTo(characterUI);
        }

        if(Input.GetKeyDown(KeyCode.B))
        {
            SwitchWithKeyTo(craftUI);
        }

        if(Input.GetKeyDown(KeyCode.K))
        {
            SwitchWithKeyTo(skillTreeUI);
        }

        if(Input.GetKeyDown(KeyCode.O))
        {
            SwitchWithKeyTo(optionsUI);
        }    
    }

    public void SwitchTo(GameObject _menu)//切换窗口函数
    {
        for (int i = 0; i < transform.childCount; i++)
        {
            transform.GetChild(i).gameObject.SetActive(false);
        }

        if (_menu != null)
        {
            _menu.SetActive(true);
        }
    }

    public void SwitchWithKeyTo(GameObject _menu)//键盘切换窗口函数
    {
        if (_menu != null && _menu.activeSelf)//通过判断是否传入mune和mune是否激活来决定使设置为可视或不可使
        {
            _menu.SetActive(false);
            return;
        }

        SwitchTo(_menu);
    }
}

Ui_SkillToolTip.cs

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

public class Ui_SkillToolTip : MonoBehaviour//制作一个可以检查每个技能的描述的窗口
{
    [SerializeField] private TextMeshProUGUI skillDescription;
    [SerializeField] private TextMeshProUGUI skillName;

    public void ShowToolTip(string _skillDescription,string _skillName)
    {
        skillDescription.text = _skillDescription;
        skillName.text = _skillName;
        gameObject.SetActive(true);
    }

    public void HideToolTip() => gameObject.SetActive(false);
}

UI_SkillTreeSlot.cs

using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;
using UnityEngine.WSA;

public class UI_SkillTreeSlot : MonoBehaviour,IPointerEnterHandler,IPointerExitHandler
{
    [SerializeField] private string skillName;
    [TextArea]
    [SerializeField] private string skillDescription;
    [SerializeField] private Color lockedSkillColor;

    private UI ui;

    public bool unlocked;//一个表示是否解锁的bool值

    private Image skillImage;
    [SerializeField] private UI_SkillTreeSlot[] shouldBeUnlocked;
    [SerializeField] private UI_SkillTreeSlot[] shouldBeLocked;//应该解锁和不该解锁的Slot组和Image


    private void OnValidate()
    {
        gameObject.name = "SkillTreeSlot_UI - " + skillName;
    }

    private void Start()
    {
        skillImage = GetComponent<Image>();

        skillImage.color = lockedSkillColor;

        ui = GetComponentInParent<UI>();

        GetComponent<Button>().onClick.AddListener(() => UnlockSkillSlot());
    }

    public void UnlockSkillSlot()//一个判断此Skill是否可以解锁的函数
    {
        for(int i = 0;i < shouldBeUnlocked.Length;i++)
        {
            if (shouldBeUnlocked[i].unlocked == false)
            {
                Debug.Log("Cannot unlock skill");
                return;
            }
        }

        for(int i = 0; i < shouldBeLocked.Length; i++)
        {
            if (shouldBeLocked[i].unlocked == true)
            {
                Debug.Log("Cannot unlock skill");
                return;
            }
        }

        unlocked = true;
        skillImage.color = Color.white;
    }

    public void OnPointerEnter(PointerEventData eventData)
    {
        ui.skillToolTip.ShowToolTip(skillDescription, skillName);

        Vector2 mousePosition = Input.mousePosition;

        float xOffset = 0;
        float yOffset = 0;

        if(mousePosition.x > 600)
        {
            xOffset = -150;
        }
        else
        {
            xOffset = 150;
        }
        if(mousePosition.y > 200)
        {
            yOffset = -100;
        }
        else
        {
            yOffset = 100;
        }

        ui.skillToolTip.transform.position = new Vector2(mousePosition.x + xOffset, mousePosition.y + yOffset);
    }

    public void OnPointerExit(PointerEventData eventData)
    {
        ui.skillToolTip.HideToolTip();
    }
}