:root {
    --primary: #58a6ff;
    --secondary: #238636;
    --dark: #0d1117;
    --darker: #161b22;
    --light: #c9d1d9;
    --lighter: #f0f6fc;
    --success: #2ea043;
    --warning: #d29922;
    --danger: #f85149;
  }
  
  * {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
  }
  
  body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--dark);
    color: var(--light);
    line-height: 1.6;
    padding: 20px;
    min-height: 100vh;
  }
  
  .container {
    width: 100%;
    max-width: 600px;
    margin: 0 auto;
    padding: 25px;
    background-color: var(--darker);
    border-radius: 15px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.3);
  }
  
  header {
    text-align: center;
    margin-bottom: 25px;
  }
  
  h1 {
    color: var(--primary);
    font-size: 1.8rem;
    margin-bottom: 5px;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
  }
  
  .subtitle {
    color: var(--light);
    opacity: 0.8;
    font-size: 0.9rem;
  }
  
  .form-group {
    margin-bottom: 20px;
  }
  
  label {
    display: block;
    margin-bottom: 8px;
    font-weight: 500;
    color: var(--light);
    display: flex;
    align-items: center;
    gap: 8px;
  }
  
  input[type="text"],
  input[type="number"],
  input[type="time"] {
    width: 100%;
    padding: 12px 15px;
    border: 1px solid #30363d;
    border-radius: 8px;
    background-color: #21262d;
    color: var(--light);
    font-size: 1rem;
    transition: all 0.3s ease;
  }
  
  input[type="text"]:focus,
  input[type="number"]:focus,
  input[type="time"]:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(88, 166, 255, 0.3);
  }
  
  /* Focus styles for better accessibility */
  button:focus-visible,
  input:focus-visible {
    outline: 2px solid var(--primary);
    outline-offset: 2px;
  }
  
  .checkbox-group {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(80px, 1fr));
    gap: 10px;
    margin-top: 10px;
  }
  
  .checkbox-group label {
    display: flex;
    align-items: center;
    gap: 5px;
    padding: 8px 10px;
    background-color: rgba(88, 166, 255, 0.1);
    border-radius: 6px;
    cursor: pointer;
    transition: all 0.2s ease;
  }
  
  .checkbox-group label:hover {
    background-color: rgba(88, 166, 255, 0.2);
  }
  
  .checkbox-group input[type="checkbox"] {
    appearance: none;
    width: 16px;
    height: 16px;
    border: 1px solid var(--primary);
    border-radius: 3px;
    cursor: pointer;
    position: relative;
  }
  
  .checkbox-group input[type="checkbox"]:checked {
    background-color: var(--primary);
  }
  
  .checkbox-group input[type="checkbox"]:checked::after {
    content: '\2713';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    color: white;
    font-size: 10px;
  }
  
  .button-group {
    display: flex;
    gap: 10px;
    margin-top: 20px;
  }
  
  .generate-btn {
    padding: 14px;
    background-color: var(--secondary);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    transition: all 0.3s ease;
    flex: 2;
  }
  
  .generate-btn:hover {
    background-color: var(--success);
    transform: translateY(-2px);
  }
  
  .clear-btn {
    padding: 14px;
    background-color: var(--danger);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    transition: all 0.3s ease;
    flex: 1;
  }
  
  .clear-btn:hover {
    opacity: 0.9;
    transform: translateY(-2px);
  }
  
  .pdf-btn {
    background-color: #dc3545;
    border-color: #dc3545;
    color: white;
  }

  .pdf-btn:hover {
    background-color: #c82333;
    border-color: #bd2130;
  }

  .notification-btn {
    background-color: #28a745 !important;
    border-color: #28a745 !important;
    color: white !important;
  }

  .notification-btn:hover {
    background-color: #218838 !important;
    border-color: #1e7e34 !important;
  }

  .notification-btn i {
    animation: bell-shake 2s infinite;
  }

  @keyframes bell-shake {
    0% { transform: rotate(0); }
    5% { transform: rotate(15deg); }
    10% { transform: rotate(-15deg); }
    15% { transform: rotate(15deg); }
    20% { transform: rotate(-15deg); }
    25% { transform: rotate(0); }
    100% { transform: rotate(0); }
  }

  .help-text {
    display: block;
    margin-top: 5px;
    color: var(--light);
    opacity: 0.7;
    font-size: 0.85rem;
  }
  
  .actions-container {
    display: flex;
    gap: 10px;
    margin-top: 20px;
    flex-wrap: wrap;
  }

  .action-btn {
    flex: 1;
    min-width: 150px;
    padding: 12px;
    background-color: var(--darker);
    color: var(--light);
    border: 1px solid var(--primary);
    border-radius: 8px;
    font-size: 0.9rem;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    transition: all 0.3s ease;
  }

  .action-btn:hover {
    background-color: var(--primary);
    color: white;
    transform: translateY(-2px);
  }

  .action-btn i {
    font-size: 1rem;
  }

  .schedule-container {
    margin-top: 30px;
    padding: 20px;
    background-color: rgba(88, 166, 255, 0.05);
    border-radius: 10px;
    border: 1px dashed rgba(88, 166, 255, 0.3);
  }
  
  .schedule-container h2 {
    color: var(--primary);
    margin-bottom: 15px;
    text-align: center;
    font-size: 1.4rem;
  }
  
  .plan {
    list-style: none;
    padding: 0;
  }
  
  .plan > li {
    background-color: rgba(88, 166, 255, 0.1);
    padding: 20px;
    border-radius: 8px;
    margin-bottom: 15px;
    border: 1px solid rgba(88, 166, 255, 0.2);
  }
  
  .plan > li > strong {
    color: var(--primary);
    font-size: 1.1rem;
    display: flex;
    align-items: center;
    gap: 8px;
    padding-bottom: 10px;
    border-bottom: 1px solid rgba(88, 166, 255, 0.2);
    margin-bottom: 15px;
  }
  
  .plan ul {
    margin-top: 10px;
    padding-left: 0;
    list-style: none;
  }
  
  .plan ul li {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px 15px;
    background-color: rgba(88, 166, 255, 0.05);
    border-radius: 6px;
    margin-bottom: 8px;
    transition: all 0.2s ease;
  }
  
  .plan ul li:hover {
    background-color: rgba(88, 166, 255, 0.1);
  }
  
  .session-subject {
    font-weight: 600;
    color: var(--light);
  }
  
  .session-time {
    color: var(--light);
    opacity: 0.8;
    font-size: 0.9rem;
  }
  
  .break-session {
    background-color: rgba(35, 134, 54, 0.1) !important;
    border-left: 3px solid var(--secondary);
  }
  
  .break-session .session-subject {
    color: var(--secondary);
  }
  
  .break-session .session-time {
    color: var(--secondary);
    opacity: 0.9;
  }
  
  .plan-info {
    background-color: rgba(88, 166, 255, 0.05);
    padding: 15px;
    border-radius: 8px;
    margin-bottom: 20px;
    border: 1px dashed rgba(88, 166, 255, 0.3);
  }
  
  .plan-info p {
    margin-bottom: 8px;
    display: flex;
    align-items: center;
    gap: 8px;
  }
  
  .plan-info p:last-child {
    margin-bottom: 0;
  }
  
  .plan-info strong {
    color: var(--primary);
  }
  
  /* Responsive Design */
  @media (max-width: 768px) {
    .container {
      padding: 15px;
    }
  
    h1 {
      font-size: 1.5rem;
    }
  
    .checkbox-group {
      grid-template-columns: repeat(auto-fill, minmax(70px, 1fr));
    }
  
    input[type="text"],
    input[type="number"] {
      padding: 10px 12px;
    }
  
    .button-group {
      flex-direction: column;
    }
  
    .generate-btn,
    .clear-btn {
      width: 100%;
    }
  
    .actions-container {
      flex-direction: column;
    }
  
    .toast {
      left: 20px;
      right: 20px;
      text-align: center;
    }
  }
  
  @media (max-width: 480px) {
    body {
      padding: 15px;
    }
  
    .container {
      padding: 15px;
    }
  
    h1 {
      font-size: 1.3rem;
    }
  
    .checkbox-group {
      grid-template-columns: repeat(3, 1fr);
    }
  
    .plan > li {
      padding: 12px;
    }
  
    .plan ul li {
      padding-left: 20px;
    }
  }
  
  /* Print Styles */
  @media print {
    body {
      background-color: white;
      color: #2d333b;
      padding: 0;
      margin: 0;
    }

    .container {
      width: 100%;
      max-width: none;
      padding: 20px;
      background-color: white;
      box-shadow: none;
    }

    header h1 {
      color: #2d333b;
      font-size: 24px;
      margin-bottom: 10px;
    }

    .subtitle {
      color: #444d56;
      margin-bottom: 20px;
    }

    .schedule-container {
      background-color: white;
      border: none;
      padding: 0;
    }

    .plan-info {
      background-color: #f6f8fa;
      border: 1px solid #e1e4e8;
      margin-bottom: 25px;
    }

    .plan-info strong {
      color: #2d333b;
    }

    .plan > li {
      background-color: white;
      border: 1px solid #e1e4e8;
      margin-bottom: 20px;
      break-inside: avoid;
      page-break-inside: avoid;
    }

    .plan > li > strong {
      color: #2d333b;
      border-bottom: 2px solid #e1e4e8;
      padding-bottom: 10px;
      margin-bottom: 15px;
    }

    .plan ul li {
      background-color: #f6f8fa;
      border: 1px solid #e1e4e8;
      margin-bottom: 8px;
    }

    .session-subject {
      color: #2d333b;
      font-weight: 600;
    }

    .session-time {
      color: #444d56;
    }

    .break-session {
      background-color: #f1f8ff !important;
      border-left: 3px solid #28a745;
    }

    .break-session .session-subject,
    .break-session .session-time {
      color: #28a745;
    }

    .form-group,
    .button-group,
    .actions-container,
    footer,
    .toast {
      display: none !important;
    }

    @page {
      margin: 1.5cm;
      size: letter;
    }
  }

  /* PDF-specific styles */
  .pdf-mode {
    background-color: white;
    padding: 20px;
    color: #2d333b;
  }

  .pdf-mode .container {
    background-color: white;
    box-shadow: none;
    padding: 0;
  }

  .pdf-mode header {
    text-align: center;
    margin-bottom: 30px;
  }

  .pdf-mode header h1 {
    color: #2d333b;
    font-size: 24px;
    margin-bottom: 5px;
  }

  .pdf-mode .subtitle {
    color: #444d56;
  }

  .pdf-mode .schedule-container {
    background-color: white;
    border: none;
    padding: 0;
  }

  .pdf-mode .plan-info {
    background-color: #f6f8fa;
    border: 1px solid #e1e4e8;
  }

  .pdf-mode .plan > li {
    background-color: white;
    border: 1px solid #e1e4e8;
    margin-bottom: 20px;
    page-break-inside: avoid;
  }

  .pdf-mode .plan ul li {
    background-color: #f6f8fa;
    border: 1px solid #e1e4e8;
  }

  .pdf-mode .break-session {
    background-color: #f1f8ff !important;
    border-left: 3px solid #28a745;
  }
  
  /* Animation for schedule generation */
  @keyframes fadeIn {
    from {
      opacity: 0;
      transform: translateY(10px);
    }
    to {
      opacity: 1;
      transform: translateY(0);
    }
  }
  
  .schedule-container {
    animation: fadeIn 0.5s ease-out;
  }
  
  .toggle-btn {
    background-color: #007bff;
    color: white;
    border: none;
    padding: 10px 15px;
    cursor: pointer;
    border-radius: 5px;
  }
  
  .toggle-btn:hover {
    background-color: #0056b3;
  }
  
  footer {
    text-align: center;
    margin-top: 30px;
    color: var(--light);
    opacity: 0.7;
    font-size: 0.9rem;
  }
  
  .toast {
    position: fixed;
    bottom: 20px;
    right: 20px;
    padding: 12px 20px;
    background-color: var(--success);
    color: white;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
    transform: translateY(150%);
    transition: transform 0.3s ease;
    z-index: 1000;
  }
  
  .toast.show {
    transform: translateY(0);
  }
  
  .toast.error {
    background-color: var(--danger);
  }
  
  .time-group {
    display: grid;
    gap: 10px;
    margin-top: 10px;
  }

  .time-group label {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 0;
  }

  .time-group input[type="time"] {
    flex: 1;
    min-width: 120px;
    padding: 8px 12px;
    border-radius: 6px;
  }

  .toggle-btn {
    width: 100%;
    padding: 12px;
    background-color: var(--darker);
    color: var(--light);
    border: 1px solid var(--primary);
    border-radius: 8px;
    font-size: 1rem;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    transition: all 0.3s ease;
  }

  .toggle-btn:hover {
    background-color: rgba(88, 166, 255, 0.1);
  }

  #preferredHours {
    margin-top: 15px;
    padding: 15px;
    background-color: rgba(88, 166, 255, 0.05);
    border-radius: 8px;
    border: 1px dashed rgba(88, 166, 255, 0.3);
  }

  #preferredHours.hidden {
    display: none;
  }

  .hidden {
    display: none;
  }