perf(ux): instant 0ms reader resume, fixed height progress scrubber, and settings drawer slim down

- Persist parsed book tokens in IndexedDB with background silent verification
- Eliminate loading mask completely with instant 0ms state restoration
- Upgrade progress bar to fixed 32px touch/click target with 8px track and pointer scrub
- Remove duplicate progress slider and author footer from settings drawer
- Dynamically display book title without author prefix

Co-Authored-By: Claude Code <noreply@anthropic.com>

src/App.tsx

@@ -5,10 +5,14 @@ import { SettingsDrawer } from './components/SettingsDrawer';
 import { calculateWpm } from './core/timing';
 import { tokenizeEnglishText } from './core/tokenizer';
 import { loadSavedState, saveState } from './db';
+import { getCachedTokens, saveCachedTokens } from './db/bookCache';
 import { useKeyboardShortcuts } from './hooks/useKeyboardShortcuts';
 import { useReaderEngine } from './hooks/useReaderEngine';
 import type { FontSize, FocusState } from './types';
 
+const BOOK_FILENAME = 'The Well of Ascension.txt';
+const BOOK_TITLE = BOOK_FILENAME.replace(/\.[^/.]+$/, '');
+
 export default function App() {
   const [saved] = useState<FocusState>(() => loadSavedState());
   const [flashesPerMinute, setFlashesPerMinute] = useState<number>(
@@ -17,31 +21,61 @@ export default function App() {
   const [wordsPerChunk, setWordsPerChunk] = useState<number>(saved.wordsPerChunk);
   const [fontSize, setFontSize] = useState<FontSize>(saved.fontSize);
   const [words, setWords] = useState<string[]>([]);
-  const [isLoading, setIsLoading] = useState<boolean>(true);
   const [isSettingsOpen, setIsSettingsOpen] = useState<boolean>(false);
   const [isUserActive, setIsUserActive] = useState<boolean>(true);
   const inactivityTimerRef = useRef<number | null>(null);
 
-  // Load built-in book text
+  // Fast-path IndexedDB restore with silent background verification
   useEffect(() => {
-    async function loadBook() {
+    let isCancelled = false;
+
+    async function loadBookData() {
+      // 1. Instantly read parsed tokens from IndexedDB
+      const cached = await getCachedTokens(BOOK_FILENAME);
+      if (!isCancelled && cached && cached.tokens.length > 0) {
+        setWords(cached.tokens);
+      }
+
+      // 2. Background silent verification without blocking main thread
+      const runSilentSync = async () => {
         try {
-        const res = await fetch(
+          const res = await fetch(encodeURI(`/books/${BOOK_FILENAME}`));
-          encodeURI('/books/The Well of Ascension.txt')
+          if (!res.ok || isCancelled) return;
-        );
-        if (!res.ok) {
-          throw new Error(`Failed to load book: ${res.statusText}`);
-        }
           const text = await res.text();
-        const parsedWords = tokenizeEnglishText(text);
+          if (isCancelled) return;
-        setWords(parsedWords);
+
+          // If content length identical to cache, no need to re-tokenize
+          if (cached && cached.textLength === text.length) {
+            return;
+          }
+
+          const parsed = tokenizeEnglishText(text);
+          if (!isCancelled) {
+            setWords(parsed);
+          }
+          await saveCachedTokens(BOOK_FILENAME, parsed, text.length);
         } catch (err) {
-        console.error('Failed to load book:', err);
+          console.warn('Silent sync error:', err);
-      } finally {
+        }
-        setIsLoading(false);
+      };
+
+      if (cached && cached.tokens.length > 0) {
+        if ('requestIdleCallback' in window) {
+          window.requestIdleCallback(() => runSilentSync(), { timeout: 3000 });
+        } else {
+          setTimeout(runSilentSync, 1000);
+        }
+      } else {
+        // Cold start (no cache): fetch immediately
+        await runSilentSync();
       }
     }
-    loadBook();
+
+    loadBookData();
+
+    return () => {
+      isCancelled = true;
+    };
   }, []);
 
   // Sync state changes to localStorage
@@ -67,6 +101,11 @@ export default function App() {
   const fpmRef = useRef<number>(flashesPerMinute);
   const chunkRef = useRef<number>(wordsPerChunk);
   const fontSizeRef = useRef<FontSize>(fontSize);
+  const wordsRef = useRef<string[]>(words);
+
+  useEffect(() => {
+    wordsRef.current = words;
+  }, [words]);
 
   useEffect(() => {
     fpmRef.current = flashesPerMinute;
@@ -80,19 +119,31 @@ export default function App() {
     fontSizeRef.current = fontSize;
   }, [fontSize]);
 
-  const persistCurrentState = useCallback((targetIndex?: number) => {
+  const persistCurrentState = useCallback(
+    (targetIndex?: number) => {
       const idx =
         typeof targetIndex === 'number'
           ? targetIndex
           : lastSavedIndexRef.current;
       lastSavedIndexRef.current = idx;
+
+      const curWords = wordsRef.current;
+      let chunkStr = '';
+      if (curWords.length > 0) {
+        chunkStr = curWords.slice(idx, idx + chunkRef.current).join(' ');
+      }
+
       saveState({
         wordIndex: idx,
         flashesPerMinute: fpmRef.current,
         wordsPerChunk: chunkRef.current,
         fontSize: fontSizeRef.current,
+        savedChunkText: chunkStr,
+        totalWords: curWords.length || saved.totalWords || 0,
       });
-  }, []);
+    },
+    [saved.totalWords]
+  );
 
   // Autosave periodically every 3 seconds
   useEffect(() => {
@@ -204,17 +255,74 @@ export default function App() {
     isDrawerOpen: isSettingsOpen,
   });
 
+  // Zero-millisecond instantaneous display metrics
+  const effectiveTotal =
+    totalWords > 0 ? totalWords : (saved.totalWords || 0);
+
+  const effectiveIndex = currentIndex;
+
   const progressPercent =
-    totalWords > 0
+    effectiveTotal > 0
-      ? Math.min(100, Math.max(0, (currentIndex / (totalWords - 1 || 1)) * 100))
+      ? Math.min(
+          100,
+          Math.max(0, (effectiveIndex / (effectiveTotal - 1 || 1)) * 100)
+        )
       : 0;
 
+  const activeChunkText = currentChunkText || saved.savedChunkText || '';
+
   const wpm = calculateWpm(flashesPerMinute, wordsPerChunk);
   const hudOpacity =
     isPlaying && !isUserActive
       ? 'opacity-0 pointer-events-none'
       : 'opacity-100 pointer-events-auto';
 
+  // Smooth, jitter-free fixed height progress bar interactions
+  const progressTrackRef = useRef<HTMLDivElement>(null);
+  const isDraggingRef = useRef<boolean>(false);
+
+  const seekByClientX = useCallback(
+    (clientX: number) => {
+      if (!progressTrackRef.current) return;
+      const count = totalWords > 0 ? totalWords : (saved.totalWords || 0);
+      if (count <= 0) return;
+      const rect = progressTrackRef.current.getBoundingClientRect();
+      if (rect.width <= 0) return;
+      const ratio = Math.max(0, Math.min(1, (clientX - rect.left) / rect.width));
+      const target = Math.round(ratio * (count - 1));
+      jumpTo(target);
+    },
+    [totalWords, saved.totalWords, jumpTo]
+  );
+
+  const handlePointerDown = (e: React.PointerEvent<HTMLDivElement>) => {
+    isDraggingRef.current = true;
+    try {
+      e.currentTarget.setPointerCapture(e.pointerId);
+    } catch {}
+    seekByClientX(e.clientX);
+  };
+
+  const handlePointerMove = (e: React.PointerEvent<HTMLDivElement>) => {
+    if (!isDraggingRef.current) return;
+    seekByClientX(e.clientX);
+  };
+
+  const handlePointerUp = (e: React.PointerEvent<HTMLDivElement>) => {
+    if (!isDraggingRef.current) return;
+    isDraggingRef.current = false;
+    try {
+      e.currentTarget.releasePointerCapture(e.pointerId);
+    } catch {}
+  };
+
+  const handlePointerCancel = (e: React.PointerEvent<HTMLDivElement>) => {
+    isDraggingRef.current = false;
+    try {
+      e.currentTarget.releasePointerCapture(e.pointerId);
+    } catch {}
+  };
+
   return (
     <div
       onMouseMove={resetInactivity}
@@ -226,7 +334,7 @@ export default function App() {
         className={`w-full flex items-center justify-between px-6 py-4 z-20 shrink-0 transition-opacity duration-500 ${hudOpacity}`}
       >
         <span className="text-[11px] font-mono tracking-widest text-zinc-500 uppercase">
-          The Well of Ascension
+          {BOOK_TITLE}
         </span>
 
         {/* Quiet Gear Button */}
@@ -239,18 +347,10 @@ export default function App() {
         </button>
       </header>
 
-      {/* Main RSVPs Central Stream */}
+      {/* Main RSVPs Central Stream (Instant 0ms display, zero loading mask) */}
       <main className="flex-1 min-h-0 flex items-center justify-center w-full z-10 overflow-hidden">
-        {isLoading ? (
-          <div className="flex flex-col items-center space-y-3 text-zinc-500">
-            <div className="w-6 h-6 rounded-full border-2 border-emerald-500 border-t-transparent animate-spin" />
-            <span className="text-xs font-mono tracking-wider">
-              Loading Focus...
-            </span>
-          </div>
-        ) : (
         <FocusDisplay
-            chunkText={currentChunkText}
+          chunkText={activeChunkText}
           fontSize={fontSize}
           isPlaying={isPlaying}
           onTogglePlay={() => {
@@ -258,34 +358,42 @@ export default function App() {
             togglePlay();
           }}
         />
-        )}
       </main>
 
-      {/* Bottom Ultra-Thin Progress & Speed HUD */}
+      {/* Bottom Fixed-Height Progress & Speed HUD */}
       <footer
         className={`w-full flex flex-col space-y-2 pb-4 px-6 z-20 shrink-0 transition-opacity duration-500 ${hudOpacity}`}
       >
-        {/* Ultra-thin progress line */}
+        {/* Comfortable 32px hit-box progress bar with fixed 8px inner track */}
         <div
-          onClick={(e) => {
+          ref={progressTrackRef}
-            const rect = e.currentTarget.getBoundingClientRect();
+          onPointerDown={handlePointerDown}
-            const clickPos = (e.clientX - rect.left) / rect.width;
+          onPointerMove={handlePointerMove}
-            const target = Math.round(clickPos * (totalWords - 1));
+          onPointerUp={handlePointerUp}
-            jumpTo(target);
+          onPointerCancel={handlePointerCancel}
-          }}
+          className="relative w-full h-8 flex items-center cursor-pointer select-none touch-none group"
-          className="relative w-full h-1 bg-zinc-800/80 hover:h-2 rounded-full cursor-pointer transition-all group overflow-hidden"
+          title="点击或拖拽跳转进度"
-          title="点击调整进度"
         >
+          {/* Inner track: strictly fixed 8px height, rounded-full, zero hover jitter */}
+          <div className="relative w-full h-2 bg-zinc-800/90 rounded-full">
+            {/* Filled progress bar */}
             <div
               style={{ width: `${progressPercent}%` }}
-            className="h-full bg-emerald-500 shadow-[0_0_8px_rgba(16,185,129,0.7)] transition-all duration-100"
+              className="h-full bg-emerald-500 rounded-full shadow-[0_0_8px_rgba(16,185,129,0.7)]"
             />
+
+            {/* High-contrast current position thumb marker */}
+            <div
+              style={{ left: `${progressPercent}%` }}
+              className="absolute top-1/2 -translate-y-1/2 -translate-x-1/2 w-3.5 h-3.5 bg-white border-2 border-emerald-400 rounded-full shadow-[0_0_8px_rgba(16,185,129,0.9)] pointer-events-none group-hover:scale-110 transition-transform duration-100"
+            />
+          </div>
         </div>
 
         {/* Status text */}
         <div className="flex items-center justify-between text-[11px] font-mono text-zinc-500">
           <span>
-            {(currentIndex + 1).toLocaleString()} / {totalWords.toLocaleString()}{' '}
+            {(effectiveIndex + 1).toLocaleString()} / {effectiveTotal.toLocaleString()}{' '}
             <span className="opacity-70">({progressPercent.toFixed(1)}%)</span>
           </span>
 
@@ -308,12 +416,9 @@ export default function App() {
         onChangeWordsPerChunk={handleWordsPerChunkChange}
         fontSize={fontSize}
         onChangeFontSize={handleFontSizeChange}
-        wordIndex={currentIndex}
-        totalWords={totalWords}
-        onJumpTo={jumpTo}
         onResetProgress={() => {
           restart();
-          saveState({ wordIndex: 0 });
+          persistCurrentState(0);
         }}
       />
     </div>

src/components/SettingsDrawer.tsx

@@ -12,9 +12,6 @@ interface SettingsDrawerProps {
   onChangeWordsPerChunk: (chunk: number) => void;
   fontSize: FontSize;
   onChangeFontSize: (size: FontSize) => void;
-  wordIndex: number;
-  totalWords: number;
-  onJumpTo: (index: number) => void;
   onResetProgress: () => void;
 }
 
@@ -36,18 +33,11 @@ export const SettingsDrawer: FC<SettingsDrawerProps> = ({
   onChangeWordsPerChunk,
   fontSize,
   onChangeFontSize,
-  wordIndex,
-  totalWords,
-  onJumpTo,
   onResetProgress,
 }) => {
   if (!isOpen) return null;
 
   const wpm = calculateWpm(flashesPerMinute, wordsPerChunk);
-  const progressPercent =
-    totalWords > 0
-      ? Math.min(100, Math.max(0, (wordIndex / (totalWords - 1 || 1)) * 100))
-      : 0;
 
   return (
     <div className="fixed inset-0 z-50 flex justify-end bg-black/60 backdrop-blur-sm select-none animate-in fade-in duration-200">
@@ -180,32 +170,20 @@ export const SettingsDrawer: FC<SettingsDrawerProps> = ({
             </div>
           </div>
 
-          {/* Progress Jump Scrubber */}
+          {/* Reading Progress Action */}
-          <div className="space-y-2 pt-2 border-t border-zinc-800/80">
+          <div className="pt-2 border-t border-zinc-800/80 flex items-center justify-between">
-            <div className="flex justify-between items-center text-xs font-mono">
+            <span className="text-xs font-mono uppercase tracking-wider text-zinc-400">
-              <span className="text-zinc-400 uppercase tracking-wider">Progress</span>
+              Reading Progress
-              <span className="text-zinc-300">
-                {wordIndex.toLocaleString()} / {totalWords.toLocaleString()} ({progressPercent.toFixed(1)}%)
             </span>
-            </div>
-            <input
-              type="range"
-              min={0}
-              max={Math.max(0, totalWords - 1)}
-              value={wordIndex}
-              onChange={(e) => onJumpTo(Number(e.target.value))}
-              className="w-full h-1.5 bg-zinc-800 rounded-lg appearance-none cursor-pointer accent-emerald-500 focus:outline-none"
-            />
-            <div className="flex justify-end pt-1">
             <button
               onClick={onResetProgress}
-                className="flex items-center space-x-1.5 text-xs font-mono text-zinc-400 hover:text-rose-400 transition-colors py-1 px-2 rounded hover:bg-zinc-900"
+              className="flex items-center space-x-1.5 text-xs font-mono text-zinc-400 hover:text-rose-400 transition-colors py-1.5 px-3 rounded-lg border border-zinc-800 hover:border-zinc-700 bg-zinc-900"
+              title="Reset reading position to start"
             >
               <RotateCcw className="w-3.5 h-3.5" />
               <span>Reset to Start</span>
             </button>
           </div>
-          </div>
 
           {/* Shortcuts Reference */}
           <div className="space-y-2 pt-3 border-t border-zinc-800/80 text-xs">
@@ -236,11 +214,6 @@ export const SettingsDrawer: FC<SettingsDrawerProps> = ({
             </div>
           </div>
         </div>
-
-        {/* Footer info */}
-        <div className="pt-4 border-t border-zinc-800/60 text-center text-[11px] font-mono text-zinc-600">
-          The Well of Ascension · Brandon Sanderson
-        </div>
       </div>
     </div>
   );

src/db/bookCache.ts

@@ -0,0 +1,90 @@
+const DB_NAME = 'focus_tokens_db';
+const STORE_NAME = 'tokens_cache';
+const DB_VERSION = 1;
+
+interface CachedBookRecord {
+  bookKey: string;
+  tokens: string[];
+  textLength: number;
+  updatedAt: number;
+}
+
+function openDatabase(): Promise<IDBDatabase> {
+  return new Promise((resolve, reject) => {
+    if (typeof indexedDB === 'undefined') {
+      return reject(new Error('IndexedDB not supported'));
+    }
+    const request = indexedDB.open(DB_NAME, DB_VERSION);
+
+    request.onupgradeneeded = () => {
+      const db = request.result;
+      if (!db.objectStoreNames.contains(STORE_NAME)) {
+        db.createObjectStore(STORE_NAME, { keyPath: 'bookKey' });
+      }
+    };
+
+    request.onsuccess = () => resolve(request.result);
+    request.onerror = () => reject(request.error);
+  });
+}
+
+/**
+ * Retrieve cached token array and metadata from IndexedDB.
+ */
+export async function getCachedTokens(
+  bookKey: string
+): Promise<{ tokens: string[]; textLength: number } | null> {
+  try {
+    const db = await openDatabase();
+    return new Promise((resolve) => {
+      const tx = db.transaction(STORE_NAME, 'readonly');
+      const store = tx.objectStore(STORE_NAME);
+      const req = store.get(bookKey);
+
+      req.onsuccess = () => {
+        const res = req.result as CachedBookRecord | undefined;
+        if (res && Array.isArray(res.tokens) && res.tokens.length > 0) {
+          resolve({
+            tokens: res.tokens,
+            textLength: typeof res.textLength === 'number' ? res.textLength : 0,
+          });
+        } else {
+          resolve(null);
+        }
+      };
+
+      req.onerror = () => resolve(null);
+    });
+  } catch (err) {
+    console.warn('Failed to read tokens from IndexedDB:', err);
+    return null;
+  }
+}
+
+/**
+ * Persist parsed tokens and content length into IndexedDB.
+ */
+export async function saveCachedTokens(
+  bookKey: string,
+  tokens: string[],
+  textLength: number
+): Promise<void> {
+  try {
+    const db = await openDatabase();
+    return new Promise((resolve, reject) => {
+      const tx = db.transaction(STORE_NAME, 'readwrite');
+      const store = tx.objectStore(STORE_NAME);
+      const record: CachedBookRecord = {
+        bookKey,
+        tokens,
+        textLength,
+        updatedAt: Date.now(),
+      };
+      const req = store.put(record);
+      req.onsuccess = () => resolve();
+      req.onerror = () => reject(req.error);
+    });
+  } catch (err) {
+    console.warn('Failed to save tokens to IndexedDB:', err);
+  }
+}

src/db/index.ts

@@ -7,6 +7,8 @@ export const DEFAULT_STATE: FocusState = {
   wordsPerChunk: 2,
   flashesPerMinute: 250,
   fontSize: 'xl',
+  savedChunkText: '',
+  totalWords: 0,
 };
 
 export function loadSavedState(): FocusState {
@@ -36,6 +38,10 @@ export function loadSavedState(): FocusState {
           )
         ),
         fontSize: parsed.fontSize || 'xl',
+        savedChunkText:
+          typeof parsed.savedChunkText === 'string' ? parsed.savedChunkText : '',
+        totalWords:
+          typeof parsed.totalWords === 'number' ? parsed.totalWords : 0,
       };
     }
   } catch (err) {

src/types/index.ts

@@ -11,4 +11,6 @@ export interface FocusState {
   wordsPerChunk: number;
   flashesPerMinute: number;
   fontSize: FontSize;
+  savedChunkText?: string;
+  totalWords?: number;
 }