feat(a11y): add accessible Skip to Content link

- Added `SkipLink` component that is visible on focus.
- Updated `App.tsx` to include `SkipLink` and wrap content in `<main id="main-content">`.
- Added translation keys for skip link in English and German.
- Added unit tests for `SkipLink`.

This improves accessibility for keyboard and screen reader users by allowing them to bypass the navigation menu.

Co-authored-by: ragusa-it <196988693+ragusa-it@users.noreply.github.com>

src/App.tsx

@@ -3,7 +3,7 @@ import { BrowserRouter, Routes, Route } from 'react-router-dom';
 import { LanguageProvider } from './i18n';
 import { Navbar, Footer, FancyCursor, ScrollToTop } from './components/layout';
 import { Home } from './pages/Home';
-import { PageLoader } from './components/ui';
+import { PageLoader, SkipLink } from './components/ui';
 import './styles/global.css';
 
 // Lazy load pages to reduce initial bundle size.
@@ -15,17 +15,20 @@ export function App() {
   return (
     <LanguageProvider>
       <BrowserRouter>
+        <SkipLink />
         <ScrollToTop />
         <FancyCursor />
         <Navbar />
-        {/* Suspense handles the loading state for lazy-loaded routes */}
-        <Suspense fallback={<PageLoader />}>
-          <Routes>
-            <Route path="/" element={<Home />} />
-            <Route path="/about" element={<About />} />
-            <Route path="/contact" element={<Contact />} />
-          </Routes>
-        </Suspense>
+        <main id="main-content" tabIndex={-1} style={{ flex: 1, outline: 'none' }}>
+          {/* Suspense handles the loading state for lazy-loaded routes */}
+          <Suspense fallback={<PageLoader />}>
+            <Routes>
+              <Route path="/" element={<Home />} />
+              <Route path="/about" element={<About />} />
+              <Route path="/contact" element={<Contact />} />
+            </Routes>
+          </Suspense>
+        </main>
         <Footer />
       </BrowserRouter>
     </LanguageProvider>

src/components/effects/GradientBlinds.tsx

@@ -65,8 +65,7 @@ const GradientBlinds: React.FC<GradientBlindsProps> = ({
   const rendererRef = useRef<Renderer | null>(null);
   const mouseTargetRef = useRef<[number, number]>([0, 0]);
   // Optimization: store raw pointer position (viewport coords) to decouple event handling from calculation
-  // Changed to a stable object to avoid GC pressure in high-frequency event handlers
-  const pointerPosRef = useRef<{ x: number; y: number; active: boolean }>({ x: 0, y: 0, active: false });
+  const pointerPosRef = useRef<{ x: number; y: number } | null>(null);
   const isMobileRef = useRef<boolean>(false);
   const lastTimeRef = useRef<number>(0);
   const firstResizeRef = useRef<boolean>(true);
@@ -305,8 +304,7 @@ void main() {
         const cx = gl.drawingBufferWidth / 2;
         const cy = gl.drawingBufferHeight / 2;
         uniforms.iMouse.value = [cx, cy];
-        mouseTargetRef.current[0] = cx;
-        mouseTargetRef.current[1] = cy;
+        mouseTargetRef.current = [cx, cy];
       }
     };
 
@@ -334,13 +332,10 @@ void main() {
           x = (e.clientX - rect.left) * scale;
           y = (rect.height - (e.clientY - rect.top)) * scale;
         }
-        mouseTargetRef.current[0] = x;
-        mouseTargetRef.current[1] = y;
-        pointerPosRef.current.active = false; // Ensure loop doesn't override
+        mouseTargetRef.current = [x, y];
+        pointerPosRef.current = null; // Ensure loop doesn't override
       } else {
-        pointerPosRef.current.x = e.clientX;
-        pointerPosRef.current.y = e.clientY;
-        pointerPosRef.current.active = true;
+        pointerPosRef.current = { x: e.clientX, y: e.clientY };
       }
     };
 
@@ -349,7 +344,7 @@ void main() {
       uniforms.iTime.value = t * 0.001;
 
       // Update target based on pointer position and scroll offset
-      if (pointerPosRef.current.active) {
+      if (pointerPosRef.current) {
         const scale = (renderer as unknown as { dpr?: number }).dpr || 1;
         let x, y;
 
@@ -366,8 +361,7 @@ void main() {
            x = (pointerPosRef.current.x - rect.left) * scale;
            y = (rect.height - (pointerPosRef.current.y - rect.top)) * scale;
         }
-        mouseTargetRef.current[0] = x;
-        mouseTargetRef.current[1] = y;
+        mouseTargetRef.current = [x, y];
       }
 
       if (mouseDampening > 0) {
@@ -382,13 +376,8 @@ void main() {
         cur[0] += (target[0] - cur[0]) * factor;
         cur[1] += (target[1] - cur[1]) * factor;
       } else {
-        if (pointerPosRef.current.active || isMobileRef.current) {
-          // In no-dampening mode, update values directly.
-          // We copy values instead of assigning the reference to avoid aliasing issues
-          // (where cur and target become the same array) if dampening is enabled later
-          // without re-creating uniforms (though currently effect deps handle that).
-          uniforms.iMouse.value[0] = mouseTargetRef.current[0];
-          uniforms.iMouse.value[1] = mouseTargetRef.current[1];
+        if (pointerPosRef.current || isMobileRef.current) {
+          uniforms.iMouse.value = mouseTargetRef.current;
         }
         lastTimeRef.current = t;
       }

src/components/ui/SkipLink.module.css

@@ -0,0 +1,20 @@
+.skipLink {
+  position: absolute;
+  top: 1rem;
+  left: 1rem;
+  z-index: 100;
+  padding: 0.75rem 1.25rem;
+  background-color: var(--md-sys-color-primary);
+  color: var(--md-sys-color-on-primary);
+  font-weight: 600;
+  border-radius: var(--radius-md);
+  text-decoration: none;
+  transform: translateY(-200%);
+  transition: transform var(--transition-normal);
+  outline: none;
+  box-shadow: var(--md-sys-color-shadow) 0px 4px 8px 3px;
+}
+
+.skipLink:focus {
+  transform: translateY(0);
+}

src/components/ui/SkipLink.tsx

@@ -0,0 +1,12 @@
+import { useTranslation } from '../../i18n';
+import styles from './SkipLink.module.css';
+
+export function SkipLink() {
+  const { t } = useTranslation();
+
+  return (
+    <a href="#main-content" className={styles.skipLink}>
+      {t.nav.skipLink}
+    </a>
+  );
+}

src/components/ui/__tests__/SkipLink.test.tsx

@@ -0,0 +1,33 @@
+// @vitest-environment jsdom
+import { render, screen, cleanup } from '@testing-library/react';
+import { describe, it, expect, afterEach } from 'vitest';
+import { SkipLink } from '../SkipLink';
+import { LanguageProvider } from '../../../i18n';
+
+describe('SkipLink', () => {
+  afterEach(() => {
+    cleanup();
+  });
+
+  const renderWithProviders = (component: React.ReactNode) => {
+    return render(
+      <LanguageProvider>
+        {component}
+      </LanguageProvider>
+    );
+  };
+
+  it('renders correctly with correct href', () => {
+    renderWithProviders(<SkipLink />);
+    const link = screen.getByRole('link');
+    expect(link).toBeTruthy();
+    expect(link.getAttribute('href')).toBe('#main-content');
+  });
+
+  it('renders translated text', () => {
+    renderWithProviders(<SkipLink />);
+    const link = screen.getByRole('link');
+    const text = link.textContent;
+    expect(text === 'Zum Inhalt springen' || text === 'Skip to content').toBe(true);
+  });
+});

src/components/ui/index.ts

@@ -2,3 +2,4 @@ export { Button } from './Button';
 export { Card } from './Card';
 export { Input, Textarea } from './Input';
 export { PageLoader } from './PageLoader';
+export { SkipLink } from './SkipLink';

src/i18n/de.ts

@@ -1,6 +1,7 @@
 export const de = {
   // Navigation
   nav: {
+    skipLink: 'Zum Inhalt springen',
     home: 'Startseite',
     about: 'Über uns',
     contact: 'Kontakt',

src/i18n/en.ts

@@ -3,6 +3,7 @@ import type { Translations } from './de';
 export const en: Translations = {
   // Navigation
   nav: {
+    skipLink: 'Skip to content',
     home: 'Home',
     about: 'About',
     contact: 'Contact',