ui基本完毕，修了一大把的bug

Assets/scripts/gamePlay_gameplay/NoteSpawner.cs

@@ -100,6 +100,7 @@ public class NoteSpawner : MonoBehaviour
     private Dictionary<int, int> noteIndexToHoldId = new Dictionary<int, int>();
 
     private const string NoteSpeedPrefKey = "noteSpeedMultiplier";
+    private const float NoteSpeedDefault = 1f;
     private const float BaseTravelDistance = 10.75f;
 
     private Coroutine spawnCoroutine;
@@ -118,13 +119,25 @@ public class NoteSpawner : MonoBehaviour
 
     private void Awake()
     {
+        EnsureDefaultNoteSpeedPreference();
         // Load saved visual speed multiplier before any spawning logic uses it
-        float saved = PlayerPrefs.GetFloat(NoteSpeedPrefKey, speedMultiplier);
+        float saved = PlayerPrefs.GetFloat(NoteSpeedPrefKey, NoteSpeedDefault);
         saved = Mathf.Clamp(saved, SpeedMultiplierMin, SpeedMultiplierMax);
         speedMultiplier = saved;
         if (JudgeManager.IsDebugEnabled) Debug.Log($"[NoteSpawner] Loaded speedMultiplier={speedMultiplier} from PlayerPrefs");
     }
 
+    private static void EnsureDefaultNoteSpeedPreference()
+    {
+        if (PlayerPrefs.HasKey(NoteSpeedPrefKey))
+        {
+            return;
+        }
+
+        PlayerPrefs.SetFloat(NoteSpeedPrefKey, NoteSpeedDefault);
+        PlayerPrefs.Save();
+    }
+
     private void OnEnable()
     {
         // Documentation text normalized.
@@ -429,7 +442,7 @@ public class NoteSpawner : MonoBehaviour
         }
 
         int segmentCount = Mathf.CeilToInt(noteData.length / segmentInterval);
-        if (segmentCount < 1) segmentCount = 1; // Documentation text normalized.
+        if (segmentCount < 2) segmentCount = 2; // Force at least one middle segment between start and end.
         float actualSegmentInterval = segmentCount > 0 ? noteData.length / segmentCount : segmentInterval;
 
         Transform spawnPoint = spawnPoints[noteData.trackIndex];