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​​

AreaSound.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;public class AreaSound : MonoBehaviour
{[SerializeField] private int areaSoundIndex;private void OnTriggerEnter2D(Collider2D collision){if(collision.GetComponent<Player>() != null){AudioManager.instance.PlaySFX(areaSoundIndex, null);}}private void OnTriggerExit2D(Collider2D collision){if(collision.GetComponent<Player>()!=null){AudioManager.instance.StopSFXWithTime(areaSoundIndex);//退出区域后，声音缓慢减少}}
}

AudioManager.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;public class AudioManager : MonoBehaviour
{public static AudioManager instance;[SerializeField] private float sfxMinimumDistance;[SerializeField] private AudioSource[] sfx;[SerializeField] private AudioSource[] bgm;public bool playBgm;private int bgmIndex;private bool canPlaySFX;//private void Awake(){if (instance != null){Destroy(instance.gameObject);}elseinstance = this;Invoke("AllowSFX", 1f);//让游戏延迟一秒后才能发出声效}private void Update(){if (!playBgm)StopAllBGM();else{if (!bgm[bgmIndex].isPlaying)PlayBGM(bgmIndex);}}public void PlaySFX(int _sfxIndex,Transform _source){//if (sfx[_sfxIndex].isPlaying)//防止出现多个相同物体同时发出声音//{//    return;//}if(canPlaySFX == false){return;}if (_source != null && Vector2.Distance(PlayerManager.instance.player.transform.position, _source.position) > sfxMinimumDistance)//防止东西很远的情况下发出声音return;if(_sfxIndex < sfx.Length){sfx[_sfxIndex].pitch = Random.Range(.85f, 1.1f);sfx[_sfxIndex].Play();}}public void StopSFX(int _sfxIndex){sfx[_sfxIndex].Stop();}public void PlayRandomBGM(){bgmIndex = Random.Range(0, bgm.Length);PlayBGM(bgmIndex);}public void PlayBGM(int _bgmIndex){bgmIndex = _bgmIndex;StopAllBGM();if (_bgmIndex < sfx.Length){bgm[_bgmIndex].Play();}}public void StopAllBGM(){for(int i = 0; i < bgm.Length; i++){bgm[i].Stop();}}private void AllowSFX(){canPlaySFX = true;}public void StopSFXWithTime(int _index){StartCoroutine(DecreaseVolume(sfx[_index]));}private IEnumerator DecreaseVolume(AudioSource _audio)//退出区域后，声音缓慢减少{float defaultVolume = _audio.volume;while (_audio.volume > .1f){_audio.volume -= _audio.volume * .2f;yield return new WaitForSeconds(.6f);if (_audio.volume <= .1f){_audio.Stop();_audio.volume = defaultVolume;break;}}}
}

UI.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;public class UI : MonoBehaviour,ISaveManager
{[Header("End screen")][SerializeField] private UI_FadeScreen fadeScreen;[SerializeField] private GameObject endText;[SerializeField] private GameObject restartButton;[Space][SerializeField] private GameObject characterUI;[SerializeField] private GameObject skillTreeUI;[SerializeField] private GameObject craftUI;[SerializeField] private GameObject optionsUI;[SerializeField] private GameObject inGameUI;public UI_itemTooltip itemToolTip;public UI_statToolTip statToopTip;public Ui_SkillToolTip skillToolTip;public UI_CraftWindow craftWindow;[SerializeField] private UI_VolumeSlider[] volumeSettings;public void Awake(){SwitchTo(skillTreeUI);//修复可能出现skill没法加载成功的bug}public void Start(){SwitchTo(inGameUI);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++){bool fadeScreen = transform.GetChild(i).GetComponent<UI_FadeScreen>() != null;//保证存在淡入淡出效果的函数时才会为真，才会使darkScreen保持存在if (!fadeScreen)transform.GetChild(i).gameObject.SetActive(false);}if (_menu != null){AudioManager.instance.PlaySFX(7,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);CheckForInGameUI();return;}SwitchTo(_menu);}private void CheckForInGameUI()//当其他UI不在时自动切换值InGameUI函数{for (int i = 0; i < transform.childCount; i++){if (transform.GetChild(i).gameObject.activeSelf && transform.GetChild(i).GetComponent<UI_FadeScreen>() == null) //修复InGameUI在fadeScreen打开后，没法存在的问题return;}SwitchTo(inGameUI);}public void SwitchOnEndScreen()//死亡综合效果函数{SwitchTo(null);fadeScreen.FadeOut();StartCoroutine(EndScreenCorutine());}IEnumerator EndScreenCorutine()//死亡显示文本函数{yield return new WaitForSeconds(1);endText.SetActive(true);yield return new WaitForSeconds(1.5f);restartButton.SetActive(true);}public void RestartGameButton()//场景重开函数{GameManager.instance.RestratScene();//调用GameManager的重开函数}public void LoadData(GameData _data){foreach(KeyValuePair<string,float> pair in _data.volumeSettings){foreach(UI_VolumeSlider item in volumeSettings){if(item.parametr == pair.Key){item.LoadSlider(pair.Value);}    }}}public void SaveData(ref GameData _data){_data.volumeSettings.Clear();foreach(UI_VolumeSlider item in volumeSettings){_data.volumeSettings.Add(item.parametr, item.slider.value);}}
}