I will continue to optimize the website with a focus on mobile responsiveness and user experience. Here is the plan:

## 1. Enhance Mobile Experience (App.vue)
- **Responsive Navigation**: Implement a "Hamburger Menu" for mobile devices. When the screen width is small, the horizontal menu will collapse into a drawer or dropdown menu.
- **Layout Adjustments**: Ensure the header and footer look good on smaller screens.

## 2. Upgrade Help Center (Help.vue)
- **Search Functionality**: Add a search bar at the top to filter FAQs.
- **Categorization**: Group FAQs into categories (e.g., "Account & Security", "Trading & Payment", "Technical Support") for better navigation.
- **UI Polish**: Improve the visual style of the help center.

## 3. Add 404 Not Found Page
- **Create `src/views/NotFound.vue`**: A friendly error page with a button to return to the home page.
- **Router Configuration**: Update `src/router/index.js` to catch unmatched routes and redirect to the 404 page.

## 4. Add Page Transitions
- **Global Transition**: Add a subtle fade-slide animation in `App.vue` when switching between routes to make the navigation feel smoother.