:root {
    --primary-color: #3498db;
    --secondary-color: #2980b9;
    --correct-color: #2ecc71;
    --incorrect-color: #e74c3c;
    --marked-color: #f39c12;
    --unanswered-color: #95a5a6;
    --light-gray: #ecf0f1;
    --dark-gray: #34495e;
    --white: #ffffff;
  }
  
  * {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  }
  
  body {
    background-color: #f5f7fa;
    color: #333;
    line-height: 1.6;
  }
  
  /* Start Screen Styles */
  .start-screen {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-color: rgba(236, 240, 241, 0.9);
  }
  
  .start-container {
    background-color: var(--white);
    padding: 30px;
    border-radius: 8px;
    box-shadow: 0 0 20px rgba(0, 0, 0, 0.1);
    max-width: 800px;
    width: 90%;
    text-align: center;
  }
  
  .start-container h1 {
    color: var(--primary-color);
    margin-bottom: 20px;
    font-size: 28px;
  }
  
  .start-container p {
    font-size: 18px;
    margin-bottom: 30px;
    color: var(--dark-gray);
  }
  
  .instructions {
    text-align: left;
    margin: 30px 0;
    padding: 20px;
    background-color: var(--light-gray);
    border-radius: 5px;
  }
  
  .instructions h3 {
    margin-bottom: 10px;
    color: var(--dark-gray);
  }
  
  .instructions ul {
    margin-left: 20px;
  }
  
  .instructions li {
    margin-bottom: 8px;
  }
  
  .start-btn {
    padding: 12px 30px;
    background-color: var(--primary-color);
    color: var(--white);
    border: none;
    border-radius: 5px;
    font-size: 18px;
    font-weight: bold;
    cursor: pointer;
    transition: all 0.2s ease;
  }
  
  .start-btn:hover {
    background-color: var(--secondary-color);
  }
  
  /* Exam Container */
  .exam-container {
    background-color: var(--white);
    box-shadow: 0 0 20px rgba(0, 0, 0, 0.1);
    overflow: hidden;
    display: none; /* Hidden initially */
  }
  
  .exam-header {
    background-color: var(--primary-color);
    color: var(--white);
    padding: 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
  }
  
  .exam-header h1 {
    font-size: 24px;
  }
  
  .timer-container {
    background-color: var(--secondary-color);
    padding: 10px 20px;
    border-radius: 30px;
    font-size: 18px;
    font-weight: bold;
  }
  
  .exam-body {
    display: flex;
    min-height: 500px;
  }
  
  /* Question Navigation */
  .question-nav {
    width: 300px;
    background-color: var(--light-gray);
    padding: 20px;
    border-right: 1px solid #ddd;
    max-height: 645px;
    height: 100%;
    overflow-y: auto;
  }
  
  .question-nav h3 {
    margin-bottom: 15px;
    color: var(--dark-gray);
  }
  
  .nav-buttons {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 8px;
  }
  
  .nav-btn {
    width: 100%;
    height: 40px;
    border: none;
    background-color: var(--white);
    border-radius: 4px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    transition: all 0.3s ease;
  }
  
  .nav-btn:hover {
    background-color: #ddd;
  }
  
  .nav-btn.answered {
    background-color: var(--primary-color);
    color: var(--white);
  }
  
  .nav-btn.marked {
    background-color: var(--marked-color);
    color: var(--white);
  }
  
  /* Question Area */
  .question-area {
    flex: 1;
    padding: 20px;
    display: flex;
    flex-direction: column;
  }
  
  .progress-container {
    margin-bottom: 20px;
    display: flex;
    align-items: center;
    gap: 15px;
  }
  
  .progress-bar {
    flex: 1;
    height: 10px;
    background-color: var(--light-gray);
    border-radius: 5px;
    overflow: hidden;
  }
  
  .progress-bar div {
    height: 100%;
    background-color: var(--primary-color);
    width: 0%;
    transition: width 0.3s ease;
  }
  
  #progress-text {
    font-weight: bold;
    color: var(--dark-gray);
  }
  
  .question-container {
    flex: 1;
  }
  
  #question-number {
    color: var(--dark-gray);
    margin-bottom: 15px;
  }
  
  #question-text {
    font-size: 18px;
    margin-bottom: 20px;
  }
  
  /* Question Image */
  .question-image-container {
    margin: 15px 0;
    text-align: center;
  }
  
  .question-image {
    max-width: 100%;
    max-height: 300px;
    border: 1px solid #ddd;
    border-radius: 4px;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
  }
  
  .image-error {
    color: var(--incorrect-color);
    font-style: italic;
    padding: 10px;
    background-color: rgba(231, 76, 60, 0.1);
    border-radius: 4px;
    display: inline-block;
  }
  
  /* Options */
  .options-container {
    display: flex;
    flex-direction: column;
    gap: 10px;
  }
  
  .option {
    display: flex;
    align-items: center;
    padding: 12px 15px;
    background-color: var(--light-gray);
    border-radius: 5px;
    cursor: pointer;
    transition: all 0.2s ease;
  }
  
  .option:hover {
    background-color: #ddd;
  }
  
  .option input {
    margin-right: 10px;
    cursor: pointer;
  }
  
  .option-label {
    font-weight: bold;
    margin-right: 5px;
    color: var(--primary-color);
  }
  
  /* Action Buttons */
  .fixed-action-buttons {
    display: flex;
    justify-content: space-between;
    margin-top: 20px;
    gap: 10px;
    padding-top: 20px;
    border-top: 1px solid #ddd;
  }
  
  .btn {
    padding: 10px 20px;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    font-weight: bold;
    transition: all 0.2s ease;
  }
  
  .btn:not(.submit-btn) {
    background-color: var(--primary-color);
    color: var(--white);
  }
  
  .btn:hover {
    opacity: 0.9;
  }
  
  .btn:disabled {
    background-color: #bdc3c7;
    cursor: not-allowed;
  }
  
  .mark-btn {
    background-color: var(--marked-color);
    color: var(--white);
  }
  
  .submit-btn {
    background-color: var(--incorrect-color);
    color: var(--white);
  }
  
  /* Results Modal */
  .modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    z-index: 1000;
    justify-content: center;
    align-items: center;
  }
  
  .modal-content {
    background-color: var(--white);
    padding: 30px;
    border-radius: 8px;
    max-width: 500px;
    width: 90%;
    text-align: center;
  }
  
  .modal-content h2 {
    margin-bottom: 20px;
    color: var(--dark-gray);
  }
  
  .result-stats {
    margin-bottom: 20px;
    text-align: left;
  }
  
  .result-stats p {
    margin-bottom: 10px;
    font-size: 16px;
  }
  
  .correct {
    color: var(--correct-color);
    font-weight: bold;
  }
  
  .incorrect {
    color: var(--incorrect-color);
    font-weight: bold;
  }
  
  .unanswered {
    color: var(--unanswered-color);
    font-weight: bold;
  }
  
  .score {
    font-size: 20px;
    font-weight: bold;
    margin-top: 15px;
    color: var(--primary-color);
  }
  
  /* Responsive Styles */
  @media (max-width: 768px) {
    .exam-body {
      flex-direction: column;
    }
  
    .question-nav {
      width: 100%;
      border-right: none;
      border-bottom: 1px solid #ddd;
      height: 180px;
    }
  
    .nav-buttons {
      grid-template-columns: repeat(10, 1fr);
    }
  
    .fixed-action-buttons {
      flex-wrap: wrap;
    }
  
    .btn {
      flex: 1;
      margin-bottom: 10px;
    }
  
    .question-image {
      max-height: 200px;
    }
  }
  
  @media (max-width: 480px) {
    .nav-buttons {
      grid-template-columns: repeat(5, 1fr);
    }
  
    .exam-header {
      flex-direction: column;
      gap: 10px;
      padding: 10px;
    }
  
    .exam-header h1 {
      font-size: 1.2rem;
    }
  
    .timer-container {
      padding: 5px 10px;
    }
  }