feat: 回到顶部按钮

Author: CodeJudge

frontend/src/App.tsx

@@ -5,6 +5,7 @@ import Footer from './components/Footer';
 import ErrorBoundary from './components/ErrorBoundary';
 import KeyboardShortcuts from './components/KeyboardShortcuts';
 import TutorialOverlay from './components/TutorialOverlay';
+import BackToTop from './components/BackToTop';
 
 const Home = lazy(() => import('./pages/Home'));
 const Login = lazy(() => import('./pages/Login'));
@@ -53,6 +54,7 @@ export default function App() {
       </main>
         <KeyboardShortcuts />
         <TutorialOverlay />
+        <BackToTop />
       </div>
   );
 }

frontend/src/components/BackToTop.tsx

@@ -0,0 +1,24 @@
+import { useState, useEffect } from 'react';
+import { ArrowUp } from 'lucide-react';
+
+export default function BackToTop() {
+  const [visible, setVisible] = useState(false);
+
+  useEffect(() => {
+    const handler = () => setVisible(window.scrollY > 400);
+    window.addEventListener('scroll', handler, { passive: true });
+    return () => window.removeEventListener('scroll', handler);
+  }, []);
+
+  if (!visible) return null;
+
+  return (
+    <button
+      onClick={() => window.scrollTo({ top: 0, behavior: 'smooth' })}
+      className="fixed bottom-8 right-8 z-50 w-10 h-10 bg-primary-600 hover:bg-primary-500 text-white rounded-full shadow-lg shadow-primary-600/25 flex items-center justify-center transition-all duration-200 hover:scale-110"
+      title="回到顶部"
+    >
+      <ArrowUp className="w-5 h-5" />
+    </button>
+  );
+}

frontend/tsconfig.tsbuildinfo

@@ -1 +1 @@
-{"root":["./src/app.tsx","./src/main.tsx","./src/components/choicequestion.tsx","./src/components/codeeditor.tsx","./src/components/dailygoal.tsx","./src/components/errorboundary.tsx","./src/components/fillblankquestion.tsx","./src/components/footer.tsx","./src/components/gamificationsection.tsx","./src/components/keyboardshortcuts.tsx","./src/components/markdownrenderer.tsx","./src/components/navbar.tsx","./src/components/problemcard.tsx","./src/components/submissionstatus.tsx","./src/components/tutorialoverlay.tsx","./src/context/authcontext.tsx","./src/context/bookmarkcontext.tsx","./src/hooks/usedocumenttitle.ts","./src/pages/admin.tsx","./src/pages/adminproblemform.tsx","./src/pages/apidocs.tsx","./src/pages/home.tsx","./src/pages/leaderboard.tsx","./src/pages/login.tsx","./src/pages/notfound.tsx","./src/pages/problemdetail.tsx","./src/pages/problems.tsx","./src/pages/profile.tsx","./src/pages/register.tsx","./src/pages/submissions.tsx","./src/pages/systemhealth.tsx","./src/services/api.ts","./src/types/index.ts"],"version":"5.9.3"}
+{"root":["./src/app.tsx","./src/main.tsx","./src/components/backtotop.tsx","./src/components/choicequestion.tsx","./src/components/codeeditor.tsx","./src/components/dailygoal.tsx","./src/components/errorboundary.tsx","./src/components/fillblankquestion.tsx","./src/components/footer.tsx","./src/components/gamificationsection.tsx","./src/components/keyboardshortcuts.tsx","./src/components/markdownrenderer.tsx","./src/components/navbar.tsx","./src/components/problemcard.tsx","./src/components/submissionstatus.tsx","./src/components/tutorialoverlay.tsx","./src/context/authcontext.tsx","./src/context/bookmarkcontext.tsx","./src/hooks/usedocumenttitle.ts","./src/pages/admin.tsx","./src/pages/adminproblemform.tsx","./src/pages/apidocs.tsx","./src/pages/home.tsx","./src/pages/leaderboard.tsx","./src/pages/login.tsx","./src/pages/notfound.tsx","./src/pages/problemdetail.tsx","./src/pages/problems.tsx","./src/pages/profile.tsx","./src/pages/register.tsx","./src/pages/submissions.tsx","./src/pages/systemhealth.tsx","./src/services/api.ts","./src/types/index.ts"],"version":"5.9.3"}