存档重构，游戏内容解锁机制；教程完善（未完成）

Assets/Scripts/UI/ChapterSelection/ChapterSelectionUI.cs

@@ -24,6 +24,11 @@ namespace Ichni.UI
         public ChapterSelectionUnit connectedChapter;
 
         public string chapterName;
+        /// <summary>
+        /// 当前章节的运行时锁定状态。仅用于 UI 表现；真正进入剧情或选曲前仍会重新调用
+        /// <see cref="UnlockSaveModule.CanAccessChapter"/>，不能把本字段作为授权依据。
+        /// </summary>
+        public bool isLocked;
         public bool isExpanded;
         public bool isDuringAnimation;
 
@@ -59,6 +64,7 @@ namespace Ichni.UI
         {
             connectedChapter = chapter;
             expansionRipple.material = new Material(rippleMaterial);
+            RefreshUnlockState();
             
             expandButton.onClick.AddListener(() =>
             {
@@ -83,6 +89,11 @@ namespace Ichni.UI
                 {
                     return;
                 }
+
+                if (!CanEnterChapter())
+                {
+                    return;
+                }
                 
                 ChapterSelectionManager.instance.currentChapter = connectedChapter;
                 AudioManager.SetSwitch(connectedChapter.chapterSwitch);
@@ -97,6 +108,11 @@ namespace Ichni.UI
                 {
                     return;
                 }
+
+                if (!CanEnterChapter())
+                {
+                    return;
+                }
                 
                 ChapterSelectionManager.instance.currentChapter = connectedChapter;
                 AudioManager.SetSwitch(connectedChapter.chapterSwitch);
@@ -112,6 +128,36 @@ namespace Ichni.UI
             allPerfectText.text = allPerfectCount.ToString();
             beatmapProgressText.text = $"{finishedBeatmapCount}/{beatmapCount}";
         }
+
+        /// <summary>
+        /// 根据统一内容解锁服务刷新章节入口的可交互状态。
+        /// 当前 Prefab 尚无专用锁定美术，因此先禁用两个实际入口；后续补充锁图标时，
+        /// 只需读取 <see cref="isLocked"/>，无需复制解锁判断。
+        /// </summary>
+        private void RefreshUnlockState()
+        {
+            UnlockSaveModule unlockSaveModule = GameSaveManager.instance?.UnlockSaveModule;
+            isLocked = unlockSaveModule == null || !unlockSaveModule.CanAccessChapter(connectedChapter);
+
+            if (enterStorylineButton != null)
+            {
+                enterStorylineButton.interactable = !isLocked;
+            }
+
+            if (enterSongSelectionButton != null)
+            {
+                enterSongSelectionButton.interactable = !isLocked;
+            }
+        }
+
+        /// <summary>
+        /// 章节的最终入口检查。即使 UI Button 状态被其它脚本意外恢复，也不能绕过解锁规则。
+        /// </summary>
+        private bool CanEnterChapter()
+        {
+            RefreshUnlockState();
+            return !isLocked;
+        }
         
         private void Expand()
         {
@@ -197,4 +243,4 @@ namespace Ichni.UI
             shrinkSequence.Play();
         }
     }
-}
+}

Assets/Scripts/UI/Elements/SelectionBox.cs

@@ -0,0 +1,114 @@
+using System;
+using System.Collections.Generic;
+using DG.Tweening;
+using TMPro;
+using UnityEngine;
+using UnityEngine.Events;
+
+namespace Ichni.Menu.UI
+{
+    /// <summary>
+    /// 可复用的多选弹窗元素。调用方提供标题、内容与任意数量的 <see cref="SelectionBoxOption"/>，
+    /// 本类动态实例化对应按钮，并确保一次显示最多只会执行一个选项回调。
+    /// </summary>
+    public class SelectionBox : MonoBehaviour
+    {
+        [Header("Selection Box")]
+        public CanvasGroup canvasGroup;
+        public TMP_Text titleText;
+        public TMP_Text contentText;
+        public RectTransform optionContainer;
+        public SelectionBoxButton optionButtonPrefab;
+
+        private readonly List<SelectionBoxButton> _generatedButtons = new();
+        private bool _isResolved;
+
+        /// <summary>
+        /// 选项被选择并且自身淡出结束后触发。页面容器使用它销毁本次生成的 SelectionBox。
+        /// </summary>
+        public event Action<SelectionBox> Closed;
+
+        private void Awake()
+        {
+            canvasGroup ??= GetComponent<CanvasGroup>();
+        }
+
+        /// <summary>
+        /// 根据运行时选项初始化弹窗。至少需要一个选项；失败时返回 false，且不会显示半配置的弹窗。
+        /// </summary>
+        public bool SetUp(string title, string content, IReadOnlyList<SelectionBoxOption> options)
+        {
+            if (canvasGroup == null || optionContainer == null || optionButtonPrefab == null ||
+                options == null || options.Count == 0)
+            {
+                Debug.LogWarning("[SelectionBox] 缺少 CanvasGroup、选项容器、选项按钮预制体，或未提供任何选项。");
+                return false;
+            }
+
+            ClearGeneratedButtons();
+            _isResolved = false;
+
+            if (titleText != null) titleText.text = title ?? string.Empty;
+            if (contentText != null) contentText.text = content ?? string.Empty;
+
+            foreach (SelectionBoxOption option in options)
+            {
+                SelectionBoxButton button = Instantiate(optionButtonPrefab, optionContainer);
+                _generatedButtons.Add(button);
+                button.SetUp(option.label, () => Select(option.action));
+            }
+
+            gameObject.SetActive(true);
+            canvasGroup.alpha = 0f;
+            canvasGroup.interactable = true;
+            canvasGroup.blocksRaycasts = true;
+            canvasGroup.DOFade(1f, 0.2f).Play();
+            return true;
+        }
+
+        private void Select(UnityAction action)
+        {
+            if (_isResolved) return;
+            _isResolved = true;
+
+            // 先禁用所有输入，再执行回调。回调可以触发存档、场景切换或打开下一层 UI，
+            // 因而不能让同一帧内的其它按钮再次触发。
+            canvasGroup.interactable = false;
+            canvasGroup.blocksRaycasts = false;
+            foreach (SelectionBoxButton button in _generatedButtons)
+            {
+                if (button?.button != null)
+                    button.button.interactable = false;
+            }
+
+            action?.Invoke();
+            canvasGroup.DOFade(0f, 0.2f).OnComplete(() => Closed?.Invoke(this)).Play();
+        }
+
+        private void ClearGeneratedButtons()
+        {
+            foreach (SelectionBoxButton button in _generatedButtons)
+            {
+                if (button != null)
+                    Destroy(button.gameObject);
+            }
+
+            _generatedButtons.Clear();
+        }
+    }
+
+    /// <summary>
+    /// SelectionBox 的单个运行时选项。它不序列化到场景或存档；显示时由调用方临时创建。
+    /// </summary>
+    public readonly struct SelectionBoxOption
+    {
+        public readonly string label;
+        public readonly UnityAction action;
+
+        public SelectionBoxOption(string label, UnityAction action)
+        {
+            this.label = label;
+            this.action = action;
+        }
+    }
+}

Assets/Scripts/UI/Elements/SelectionBox.cs.meta

@@ -0,0 +1,2 @@
+fileFormatVersion: 2
+guid: 5ac6b73d890a4a7aaed8e2fa64001764

Assets/Scripts/UI/Elements/SelectionBoxButton.cs

@@ -0,0 +1,40 @@
+using TMPro;
+using UnityEngine;
+using UnityEngine.Events;
+using UnityEngine.UI;
+
+namespace Ichni.Menu.UI
+{
+    /// <summary>
+    /// SelectionBox 动态生成的单个选项按钮。
+    /// 预制体只需提供 Button 和 TMP 文本；运行时由 <see cref="SelectionBox"/> 写入显示文字与点击回调。
+    /// </summary>
+    public class SelectionBoxButton : MonoBehaviour
+    {
+        public Button button;
+        public TMP_Text labelText;
+
+        /// <summary>
+        /// 重新绑定按钮文字与本次 SelectionBox 的选择回调。
+        /// 每次生成时都会清空旧监听，防止对象复用或预制体事件造成重复触发。
+        /// </summary>
+        public void SetUp(string label, UnityAction onSelected)
+        {
+            button ??= GetComponent<Button>();
+            labelText ??= GetComponentInChildren<TMP_Text>(true);
+
+            if (labelText != null)
+                labelText.text = label ?? string.Empty;
+
+            if (button == null)
+            {
+                Debug.LogWarning("[SelectionBoxButton] 选项预制体缺少 Button 组件。");
+                return;
+            }
+
+            button.onClick.RemoveAllListeners();
+            button.onClick.AddListener(() => onSelected?.Invoke());
+            button.interactable = true;
+        }
+    }
+}

Assets/Scripts/UI/Elements/SelectionBoxButton.cs.meta

@@ -0,0 +1,2 @@
+fileFormatVersion: 2
+guid: b2c45ae5390d4a4aa16e62b5704dbf0a

Assets/Scripts/UI/Elements/SelectionBoxUIPage.cs

@@ -0,0 +1,73 @@
+using System.Collections.Generic;
+using Ichni.UI;
+using UnityEngine;
+
+namespace Ichni.Menu.UI
+{
+    /// <summary>
+    /// 通用 SelectionBox 的页面宿主，职责等同于 MessageBox 的页面容器：
+    /// 显示时动态生成一个 SelectionBox，选择完成后统一淡出并销毁本次实例。
+    /// </summary>
+    public class SelectionBoxUIPage : UIPageBase
+    {
+        [Header("Selection Box Page")]
+        public SelectionBox selectionBoxPrefab;
+        public RectTransform selectionBoxContainer;
+
+        private SelectionBox _currentSelectionBox;
+        private bool _isShowing;
+
+        /// <summary>当前是否已有一个 SelectionBox 等待玩家选择。</summary>
+        public bool IsShowing => _isShowing;
+
+        /// <summary>
+        /// 生成并显示一组运行时选项。页面显示期间拒绝重复请求，避免两个弹窗争夺输入。
+        /// </summary>
+        public bool Show(string title, string content, IReadOnlyList<SelectionBoxOption> options)
+        {
+            if (_isShowing)
+            {
+                Debug.LogWarning("[SelectionBoxUIPage] 已有 SelectionBox 显示中，忽略重复请求。");
+                return false;
+            }
+
+            if (mainCanvasGroup == null || selectionBoxPrefab == null || selectionBoxContainer == null)
+            {
+                Debug.LogWarning("[SelectionBoxUIPage] 缺少 CanvasGroup、SelectionBox Prefab 或容器，无法显示选项框。");
+                return false;
+            }
+
+            _currentSelectionBox = Instantiate(selectionBoxPrefab, selectionBoxContainer);
+            _currentSelectionBox.Closed += HandleSelectionBoxClosed;
+            if (!_currentSelectionBox.SetUp(title, content, options))
+            {
+                Destroy(_currentSelectionBox.gameObject);
+                _currentSelectionBox = null;
+                return false;
+            }
+
+            _isShowing = true;
+
+            // UIPageBase 默认淡入完成后才开启射线；选择框从出现瞬间就必须阻断底层输入。
+            mainCanvasGroup.gameObject.SetActive(true);
+            mainCanvasGroup.interactable = true;
+            mainCanvasGroup.blocksRaycasts = true;
+            FadeIn();
+            return true;
+        }
+
+        private void HandleSelectionBoxClosed(SelectionBox selectionBox)
+        {
+            if (selectionBox != _currentSelectionBox) return;
+
+            FadeOut(0.2f, false, () =>
+            {
+                if (_currentSelectionBox != null)
+                    Destroy(_currentSelectionBox.gameObject);
+
+                _currentSelectionBox = null;
+                _isShowing = false;
+            });
+        }
+    }
+}

Assets/Scripts/UI/Elements/SelectionBoxUIPage.cs.meta

@@ -0,0 +1,2 @@
+fileFormatVersion: 2
+guid: e8b607f8c5654e1eb3bf1f7ca33fd3a4

Assets/Scripts/UI/SongSelection/DifficultySelectionButton.cs

@@ -3,6 +3,7 @@ using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
 using DG.Tweening;
+using Ichni.RhythmGame;
 using Sirenix.OdinInspector;
 using SLSUtilities.WwiseAssistance;
 using TMPro;
@@ -53,11 +54,21 @@ namespace Ichni.Menu
         {
             MenuManager.instance.songSelectionUIPage.selectedDifficulty = difficultyData;
             MenuManager.instance.songSelectionUIPage.songInfoUI.SetCharter(difficultyData.charterName);
-            MenuManager.instance.songSelectionUIPage.songInfoUI.SetBeatmapInfo(
-                MenuManager.instance.songSelectionUIPage.selectedSave.beatmapSaves[difficultyData.difficultyIndex]);
+            if (MenuManager.instance.songSelectionUIPage.selectedSave.TryGetBeatmapSave(
+                    difficultyData.saveDifficultyId, out BeatmapSave beatmapSave))
+            {
+                MenuManager.instance.songSelectionUIPage.songInfoUI.SetBeatmapInfo(beatmapSave);
+            }
+            else
+            {
+                // 当前内容尚未创建该难度的记录时，UI 只显示空成绩，不在展示路径修改存档。
+                MenuManager.instance.songSelectionUIPage.songInfoUI.SetBeatmapInfo(new BeatmapSave(0f, false, false));
+            }
             
-            MenuInformationRecorder.instance.songSelectionRecords[ChapterSelectionManager.instance.currentChapter] = 
-                new SongSelectionRecord(MenuManager.instance.songSelectionUIPage.selectedSong, difficultyData);
+            MenuInformationRecorder.instance.SetRecordForChapter(
+                ChapterSelectionManager.instance.currentChapter,
+                MenuManager.instance.songSelectionUIPage.selectedSong,
+                MenuManager.instance.songSelectionUIPage.selectedSong.difficultyDataList.IndexOf(difficultyData));
 
             if (container.selectedButton == this)
             {
@@ -67,7 +78,6 @@ namespace Ichni.Menu
             
             MenuManager.instance.songSelectionUIPage.difficultySelectionContainer.selectedButton?.Deselect();
             MenuManager.instance.songSelectionUIPage.difficultySelectionContainer.selectedButton = this;
-            MenuInformationRecorder.instance.GetRecordOfThisChapter().difficultyIndex = difficultyData.difficultyIndex;
             
             AudioManager.Post(AK.EVENTS.SELECTDIFFICULTY);
            

Assets/Scripts/UI/SongSelection/DifficultySelectionContainer.cs

@@ -1,5 +1,5 @@
-using System.Collections;
 using System.Collections.Generic;
+using System;
 using UnityEngine;
 
 namespace Ichni.Menu
@@ -9,28 +9,123 @@ namespace Ichni.Menu
         public List<DifficultySelectionButton> buttons;
         public DifficultySelectionButton selectedButton;
 
+        /// <summary>
+        /// 在当前歌曲中解析一个可实际游玩的难度。
+        /// <para>preferredListIndex 是 <see cref="SongSelectionRecord.difficultyListIndex"/>，即难度在当前歌曲
+        /// List 中的位置；它不能替代 <see cref="DifficultyData.saveDifficultyId"/>，后者是游戏记录的稳定 ID。</para>
+        /// <para>规则：只考虑已配置 Button 且 <c>isAvailable</c> 为 true 的难度，优先选择与目标位置距离最小者；
+        /// 距离相同则选择位置较低者。因此目标难度不存在时，玩家会落到最接近、且偏低的可用难度。</para>
+        /// </summary>
+        private bool TryResolveAvailableDifficultyIndex(
+            IReadOnlyList<DifficultyData> difficulties,
+            int preferredListIndex,
+            out int resolvedListIndex)
+        {
+            resolvedListIndex = -1;
+            if (difficulties == null || buttons == null)
+            {
+                return false;
+            }
+
+            int candidateCount = Mathf.Min(difficulties.Count, buttons.Count);
+            long bestDistance = long.MaxValue;
+
+            for (int index = 0; index < candidateCount; index++)
+            {
+                DifficultyData difficulty = difficulties[index];
+                if (difficulty == null || !difficulty.isAvailable || buttons[index] == null)
+                {
+                    continue;
+                }
+
+                long distance = Math.Abs((long)index - preferredListIndex);
+                if (distance < bestDistance || (distance == bestDistance && index < resolvedListIndex))
+                {
+                    bestDistance = distance;
+                    resolvedListIndex = index;
+                }
+            }
+
+            return resolvedListIndex >= 0;
+        }
+
+        /// <summary>
+        /// 清除当前的难度选择，并同时关闭标准的进入游戏按钮。
+        /// SongSelectionTab 的快速进入入口也会单独检查 <c>selectedDifficulty</c>，避免绕过此 UI 状态。
+        /// </summary>
+        private void ClearDifficultySelection()
+        {
+            selectedButton?.Deselect();
+            selectedButton = null;
+
+            SongSelectionUIPage songSelectionUIPage = MenuManager.instance.songSelectionUIPage;
+            songSelectionUIPage.selectedDifficulty = null;
+            songSelectionUIPage.playSongUI.SetEnterGameAvailable(false);
+        }
+
+        /// <summary>
+        /// 根据当前歌曲刷新难度按钮，并将章节内存缓存解析为一个实际可玩的难度。
+        /// 该方法用于首次进入、从游戏返回以及拖动切歌，所以所有自动难度回退都必须经过此处。
+        /// </summary>
         public void SetUp(List<DifficultyData> difficulties)
         {
-            int difficultyCount = difficulties.Count;
+            int difficultyCount = difficulties?.Count ?? 0;
+            int buttonCount = buttons?.Count ?? 0;
 
-            for (var i = 0; i < buttons.Count; i++)
+            ClearDifficultySelection();
+
+            if (difficultyCount > buttonCount)
             {
-                buttons[i].gameObject.SetActive(i < difficultyCount);
+                Debug.LogError($"Song '{MenuManager.instance.songSelectionUIPage.selectedSong?.songName}' has {difficultyCount} difficulties but only {buttonCount} difficulty buttons. " +
+                               "Only difficulties with configured buttons can be selected.");
             }
 
-            for (int i = 0; i < difficultyCount; i++)
+            for (int i = 0; i < buttonCount; i++)
             {
-                buttons[i].SetUp(difficulties[i]);
+                DifficultySelectionButton button = buttons[i];
+                if (button == null)
+                {
+                    Debug.LogError($"Difficulty button at index {i} is missing.");
+                    continue;
+                }
+
+                bool hasDifficulty = i < difficultyCount && difficulties[i] != null;
+                button.gameObject.SetActive(hasDifficulty);
+                if (hasDifficulty)
+                {
+                    // SetUp 会进一步按 isAvailable 隐藏不可用难度。
+                    button.SetUp(difficulties[i]);
+                }
             }
 
-            SongSelectionRecord songSelectionRecord = MenuInformationRecorder.instance.GetRecordOfThisChapter();
-
-            if (songSelectionRecord.difficultyIndex >= difficultyCount)
+            if (difficultyCount == 0)
             {
-                songSelectionRecord.difficultyIndex = difficultyCount - 1;
+                Debug.LogWarning($"Song '{MenuManager.instance.songSelectionUIPage.selectedSong?.songName}' has no configured difficulties.");
+                return;
             }
 
-            buttons[songSelectionRecord.difficultyIndex % buttons.Count].Select();
+            if (!MenuInformationRecorder.instance.TryGetRecordOfThisChapter(out SongSelectionRecord songSelectionRecord))
+            {
+                Debug.LogWarning("Cannot select a difficulty because the current chapter has no valid song selection record.");
+                return;
+            }
+
+            if (!TryResolveAvailableDifficultyIndex(difficulties, songSelectionRecord.difficultyListIndex, out int resolvedListIndex))
+            {
+                Debug.LogWarning($"Song '{MenuManager.instance.songSelectionUIPage.selectedSong?.songName}' has no available difficulty to select.");
+                return;
+            }
+
+            // Select 会把实际选中的难度写回章节缓存；之后继续切歌时，以这次真实选择作为新的偏好。
+            buttons[resolvedListIndex].Select();
+
+            // 难度可用不等于内容已解锁。保持按钮状态与统一授权服务一致，
+            // 而 PlaySongUI / 快速点击仍会在真正进入前再次检查，形成双层防御。
+            UnlockSaveModule unlockSaveModule = GameSaveManager.instance?.UnlockSaveModule;
+            bool canEnterSong = unlockSaveModule != null && unlockSaveModule.CanEnterSong(
+                ChapterSelectionManager.instance?.currentChapter,
+                MenuManager.instance.songSelectionUIPage.selectedSong);
+            MenuManager.instance.songSelectionUIPage.playSongUI.SetEnterGameAvailable(canEnterSong);
         }
     }
-}
+}

Assets/Scripts/UI/SongSelection/PlaySongUI.cs

@@ -19,12 +19,37 @@ namespace Ichni.Menu
             enterGameButton.onClick.AddListener(EnterGame);
         }
 
+        /// <summary>
+        /// 设置标准 Play 按钮是否允许进入游戏。
+        /// 当当前歌曲没有可用难度时由 DifficultySelectionContainer 关闭；歌曲锁定仍沿用原有的独立判断。
+        /// </summary>
+        public void SetEnterGameAvailable(bool isAvailable)
+        {
+            enterGameButton.interactable = isAvailable;
+        }
+
         private void EnterGame()
         {
-            if (MenuManager.instance.songSelectionUIPage.songListController.selectedTab.isLocked)
+            SongSelectionUIPage songSelectionUIPage = MenuManager.instance.songSelectionUIPage;
+            SongSelectionTab selectedTab = songSelectionUIPage.songListController.selectedTab;
+
+            // 即使 Button 的 interactable 状态被错误地恢复，也不能把空难度传给 InformationTransistor。
+            if (songSelectionUIPage.selectedSong == null || songSelectionUIPage.selectedDifficulty == null || selectedTab == null)
             {
                 return;
             }
+
+            // 不能只读取 Tab 的旧显示状态。解锁 Key 可能刚被剧情授予，或 UI 状态被其它逻辑改写；
+            // 标准 Play 与快速点击都会回到 UnlockSaveModule 的同一最终授权判断。
+            UnlockSaveModule unlockSaveModule = GameSaveManager.instance?.UnlockSaveModule;
+            if (unlockSaveModule == null || !unlockSaveModule.CanEnterSong(
+                    ChapterSelectionManager.instance?.currentChapter,
+                    songSelectionUIPage.selectedSong))
+            {
+                return;
+            }
+
+            selectedTab.RefreshUnlockState();
             
             if (MenuManager.instance.isEnteringGame)
             {
@@ -34,9 +59,9 @@ namespace Ichni.Menu
             MenuManager.instance.isEnteringGame = true;
             
             InformationTransistor.instance.SetInformation(
-                ChapterSelectionManager.instance.currentChapter, 
-                MenuManager.instance.songSelectionUIPage.selectedSong, 
-                MenuManager.instance.songSelectionUIPage.selectedDifficulty);
+                ChapterSelectionManager.instance.currentChapter,
+                songSelectionUIPage.selectedSong,
+                songSelectionUIPage.selectedDifficulty);
             AudioManager.Post(AK.EVENTS.ENTERTOGAME);
             SongSelectionManager.instance.StopPreviewSong();
             
@@ -61,4 +86,4 @@ namespace Ichni.Menu
             arrowSeq.Play();
         }
     }
-}
+}

Assets/Scripts/UI/SongSelection/SongListControllerUI.cs

@@ -51,24 +51,63 @@ namespace Ichni.Menu
 
         public void InitializeList()
         {
+            // FadeOut 通常已经清理过旧 Tab，但这里仍保持幂等，防止重复初始化时残留旧引用或重复 UI。
+            ClearSongTabs();
             GenerateSongTabs();
+
+            if (songItems.Count == 0)
+            {
+                // 空 Chapter 是内容异常；运行时只进入安全状态，不访问 songItems[0]，也不允许进入游戏。
+                selectedTab = null;
+                closestTab = null;
+                topBound = content.anchoredPosition.y;
+                bottomBound = content.anchoredPosition.y;
+                targetPosition = content.anchoredPosition;
+                MenuManager.instance.songSelectionUIPage.selectedSong = null;
+                MenuManager.instance.songSelectionUIPage.selectedSave = null;
+                MenuManager.instance.songSelectionUIPage.difficultySelectionContainer.SetUp(null);
+                return;
+            }
             
             Canvas.ForceUpdateCanvases();
             topBound = (songItems.Count * 144f + (songItems.Count - 1) * 60f) - 72f; //topBound中，144为tab高度，60为tab间距，72为tab高度的一半
             bottomBound = 72f; //bottomBound中，72为tab高度的一半
 
             int songIndex = 0;
-            
-            if (MenuInformationRecorder.instance.songSelectionRecords.TryGetValue(ChapterSelectionManager.instance.currentChapter, out var record))
+            int preferredDifficultyIndex = 0;
+            ChapterSelectionUnit currentChapter = ChapterSelectionManager.instance.currentChapter;
+            MenuInformationRecorder menuInformationRecorder = MenuInformationRecorder.instance;
+
+            if (menuInformationRecorder.TryGetRecordOfThisChapter(out SongSelectionRecord record))
             {
-                songIndex = ChapterSelectionManager.instance.currentChapter.songs.FindIndex(song => song.songName == record.song.songName);
-            }
-            
-            if (songItems.Count > 0)
-            {
-                StartCoroutine(SnapToItem(songItems[songIndex], true));
+                preferredDifficultyIndex = record.difficultyListIndex;
+                SongItemData cachedSong = record.song;
+                bool cacheNeedsRepair = false;
+
+                // 优先按对象引用恢复；若缓存来自内容热更新/重建，再按 songName 进行兼容匹配。
+                songIndex = songItems.FindIndex(item => item != null && item.GetComponent<SongSelectionTab>()?.connectedSong == cachedSong);
+                if (songIndex < 0 && !string.IsNullOrEmpty(cachedSong?.songName))
+                {
+                    songIndex = songItems.FindIndex(item => item != null &&
+                        item.GetComponent<SongSelectionTab>()?.connectedSong?.songName == cachedSong.songName);
+                    cacheNeedsRepair = songIndex >= 0;
+                }
+
+                // 缓存歌曲已经被删除或改名时，立即修正缓存；难度由 SnapToItem 内的统一回退机制继续解析。
+                if (songIndex < 0)
+                {
+                    songIndex = 0;
+                    cacheNeedsRepair = true;
+                }
+
+                if (cacheNeedsRepair)
+                {
+                    SongItemData resolvedSong = songItems[songIndex].GetComponent<SongSelectionTab>().connectedSong;
+                    menuInformationRecorder.SetRecordForChapter(currentChapter, resolvedSong, preferredDifficultyIndex);
+                }
             }
             
+            StartCoroutine(SnapToItem(songItems[songIndex], true));
             closestTab = songItems[songIndex];
             
             targetPosition = content.anchoredPosition;
@@ -181,13 +220,20 @@ namespace Ichni.Menu
     {
         public void ClearSongTabs()
         {
+            StopAllCoroutines();
             foreach (RectTransform item in songItems)
             {
-                Destroy(item.gameObject);
+                if (item != null)
+                {
+                    Destroy(item.gameObject);
+                }
             }
             songItems.Clear();
             selectedTab = null;
             closestTab = null;
+            velocity = Vector2.zero;
+            isDragging = false;
+            SnapCoroutine = null;
             targetPosition = content.anchoredPosition;
             isDuringSnap = false;
         }
@@ -195,8 +241,19 @@ namespace Ichni.Menu
         public void GenerateSongTabs()
         {
             ChapterSelectionUnit chapterUnit = ChapterSelectionManager.instance.currentChapter;
+            if (chapterUnit == null || chapterUnit.songs == null)
+            {
+                return;
+            }
+
             foreach (SongItemData song in chapterUnit.songs)
             {
+                if (song == null)
+                {
+                    Debug.LogWarning("Skipped an empty song entry while generating song selection tabs.");
+                    continue;
+                }
+
                 SongSelectionTab tab = Instantiate(songItemPrefab, content).GetComponent<SongSelectionTab>();
                 songItems.Add(tab.GetComponent<RectTransform>());
                 tab.SetUpTab(song);
@@ -330,4 +387,4 @@ namespace Ichni.Menu
             isDuringSnap = false;
         }
     }
-}
+}

Assets/Scripts/UI/SongSelection/SongSelectionTab.cs

@@ -16,6 +16,10 @@ namespace Ichni.Menu
     {
         private SongListControllerUI songListController => MenuManager.instance.songSelectionUIPage.songListController;
 
+        /// <summary>
+        /// 供锁标识和预览滤镜使用的运行时状态。进入歌曲前必须调用 <see cref="RefreshUnlockState"/>
+        /// 重新计算，不能把缓存的显示状态当作最终授权结果。
+        /// </summary>
         public bool isLocked;
         
         public SongItemData connectedSong;
@@ -38,13 +42,26 @@ namespace Ichni.Menu
             songNameText.text = song.displaySongName;
             composerNameText.text = song.composer;
 
-            isLocked = !GameSaveManager.instance.SongSaveModule.CheckStoryKey(song.storyUnlockKey);
-            lockMark.gameObject.SetActive(isLocked);
+            RefreshUnlockState();
             
             quickSwitchButton.onClick.AddListener(() =>
             {
                 if (MenuManager.instance.songSelectionUIPage.songListController.selectedTab == this)
                 {
+                    SongSelectionUIPage songSelectionUIPage = MenuManager.instance.songSelectionUIPage;
+
+                    // 快速进入会绕过 PlaySongUI 的 Button.interactable，必须在此处重复保护空难度状态。
+                    if (songSelectionUIPage.selectedSong == null || songSelectionUIPage.selectedDifficulty == null)
+                    {
+                        return;
+                    }
+
+                    // 快速进入与标准 Play 共用统一的章节 + 歌曲授权检查，不能因 UI 状态过期而绕过锁定。
+                    if (!RefreshUnlockState())
+                    {
+                        return;
+                    }
+
                     if (MenuManager.instance.isEnteringGame)
                     {
                         return;
@@ -53,9 +70,9 @@ namespace Ichni.Menu
                     MenuManager.instance.isEnteringGame = true;
                     
                     InformationTransistor.instance.SetInformation(
-                        ChapterSelectionManager.instance.currentChapter, 
-                        MenuManager.instance.songSelectionUIPage.selectedSong, 
-                        MenuManager.instance.songSelectionUIPage.selectedDifficulty);
+                        ChapterSelectionManager.instance.currentChapter,
+                        songSelectionUIPage.selectedSong,
+                        songSelectionUIPage.selectedDifficulty);
                     
                     AudioManager.Post(AK.EVENTS.ENTERTOGAME);
                     SongSelectionManager.instance.StopPreviewSong();
@@ -74,6 +91,25 @@ namespace Ichni.Menu
             });
         }
 
+        /// <summary>
+        /// 重新计算当前 Tab 是否锁定，并同步锁图标。
+        /// 章节本身被锁定时，即使歌曲规则无条件开放，也仍然视为不可进入。
+        /// </summary>
+        /// <returns>返回 true 表示当前章节和歌曲均允许进入。</returns>
+        public bool RefreshUnlockState()
+        {
+            UnlockSaveModule unlockSaveModule = GameSaveManager.instance?.UnlockSaveModule;
+            ChapterSelectionUnit currentChapter = ChapterSelectionManager.instance?.currentChapter;
+            isLocked = unlockSaveModule == null || !unlockSaveModule.CanEnterSong(currentChapter, connectedSong);
+
+            if (lockMark != null)
+            {
+                lockMark.gameObject.SetActive(isLocked);
+            }
+
+            return !isLocked;
+        }
+
         private void Update()
         {
             RectTransform centerPoint = songListController.centerPoint;
@@ -113,4 +149,4 @@ namespace Ichni.Menu
             }
         }
     }
-}
+}

Assets/Scripts/UI/SongSelection/SongSelectionUIPage.cs

@@ -55,8 +55,6 @@ namespace Ichni.Menu
 
         private void Start()
         {
-            MenuInformationRecorder.instance.GetRecordOfThisChapter().difficultyIndex = 0;
-            
             Sequence framesSeq = DOTween.Sequence();
             framesSeq.Append(DOTween.To(() => framePositionOffset, x => framePositionOffset = x, 1f, 1f)
                     .SetEase(Ease.Linear)
@@ -73,4 +71,4 @@ namespace Ichni.Menu
         public DifficultyData selectedDifficulty;
         public SongStatusSave selectedSave;
     }
-}
+}