body {     margin: 0;     font-family: Arial, sans-serif;     background: linear-gradient(120deg, #0f0c29, #302b63, #24243e);     color: white;     text-align: center;     overflow: hidden; } .menu-btn {     position: fixed;     top: 20px;     left: 20px;     font-size: 30px;     cursor: pointer;     z-index: 1000; } .sidebar {     position: fixed;     top: 0;     left: -250px;     width: 200px;     height: 100%;     background: rgba(0, 0, 0, 0.8);     transition: left 0.3s;     padding-top: 50px; } .sidebar ul {     list-style: none;     padding: 0; } .sidebar li {     padding: 15px;     cursor: pointer;     transition: 0.3s; } .sidebar li:hover {     background: rgba(255, 255, 255, 0.2); } .section {     display: none;     padding: 50px;     margin-top: 100px; } .download-btn {     display: inline-block;     margin-top: 20px;     padding: 15px 30px;     background: rgba(255, 255, 255, 0.1);     border-radius: 10px;     color: white;     text-decoration: none;     transition: 0.3s; } .download-btn:hover {     background: rgba(255, 255, 255, 0.3); }