body {
      margin: 0;
      padding: 0;
      font-family: sans-serif;
      background: url('clean-quiz-background.jpg') no-repeat center center fixed;
      background-size: cover;
    }
    .container {
      max-width: 600px;
      margin: auto;
      padding: 20px;
      background-color: rgba(255,255,255,0.85);
      border-radius: 10px;
      box-shadow: 0 0 10px rgba(0,0,0,0.3);
      margin-top: 40px;
    }
    h1 {
      text-align: center;
      color: #4a7c59;
    }
    #letterDisplay {
      font-size: 4em;
      text-align: center;
      margin: 20px 0;
    }
    #question {
      font-size: 1.5em;
      text-align: center;
      margin: 10px 0;
    }
    .option {
      display: block;
      width: 100%;
      padding: 10px;
      margin: 10px 0;
      font-size: 1.2em;
      background-color: #e0f2eb;
      border: none;
      border-radius: 5px;
      cursor: pointer;
    }
    .option:hover {
      background-color: #c8e6c9;
    }
    #message {
      text-align: center;
      font-weight: bold;
      margin: 10px 0;
    }
    #nextBtn {
      display: block;
      margin: 20px auto 0;
      padding: 10px 20px;
      background-color: #4a7c59;
      color: white;
      border: none;
      border-radius: 5px;
      font-size: 1em;
      cursor: pointer;
    }