  
  <style>
    html, body {
      margin: 0;
      padding: 0;
      min-height: 100vh;
      transition: background 0.5s ease;
    }

    /* Tema 1: Biru ke Ungu */
    .bg-gradient-1 {
      background: linear-gradient(to right, #2193b0, #2193);
    }

    /* Tema 2: Merah ke Oranye */
    .bg-gradient-2 {
      background: linear-gradient(to right, #ff512f, #dd2476);
    }

    /* Tema 3: Hijau ke Kuning */
    .bg-gradient-3 {
      background: linear-gradient(to right, #56ab2f, #a8e063);
    }

    /* Tombol */
    #theme-switcher {
      position: fixed;
      top: 20px;
      right: 20px;
      padding: 10px 15px;
      font-size: 16px;
      cursor: pointer;
      background: rgba(255,255,255,0.2);
      border: 1px solid white;
      color: white;
      border-radius: 5px;
    }
  </style>
 