* {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
      font-family: 'Inter', sans-serif;
    }

    :root {
      --primary: #6366f1;
      --primary-dark: #4f46e5;
      --primary-light: #818cf8;
      --accent: #f43f5e;
      --accent-dark: #e11d48;
      --neutral-100: #0f172a;
      --neutral-200: #1e293b;
      --neutral-300: #334155;
      --neutral-700: #cbd5e1;
      --neutral-900: #f1f5f9;
      --success: #10b981;
      --card-shadow: 0 10px 30px rgba(0, 0, 0, 0.25);
      --transition: all 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);
      --border-radius: 20px;
    }

    body {
      background: linear-gradient(135deg, #0f172a 0%, #1e293b 100%);
      color: var(--neutral-900);
      min-height: 100vh;
      overflow-x: hidden;
      padding-top: 50px;
    }

    /* Cyberpunk grid background */
    .cyber-grid {
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      z-index: -2;
      opacity: 0.15;
      background-image: 
        linear-gradient(rgba(99, 102, 241, 0.2) 1px, transparent 1px),
        linear-gradient(90deg, rgba(99, 102, 241, 0.2) 1px, transparent 1px);
      background-size: 50px 50px;
      transform: perspective(500px) rotateX(60deg);
    }

    /* Floating elements */
    .floating-elements {
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      z-index: -1;
      pointer-events: none;
    }

    .floating-element {
      position: absolute;
      border-radius: 50%;
      background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
      opacity: 0.15;
      animation: float 20s infinite ease-in-out;
      filter: blur(25px);
    }

    .floating-element:nth-child(1) {
      width: 300px;
      height: 300px;
      top: 10%;
      left: 5%;
      animation-delay: 0s;
    }

    .floating-element:nth-child(2) {
      width: 200px;
      height: 200px;
      top: 65%;
      right: 8%;
      animation-delay: 5s;
    }

    .floating-element:nth-child(3) {
      width: 250px;
      height: 250px;
      bottom: 15%;
      left: 15%;
      animation-delay: 10s;
    }

    /* Marquee Banner */
    .marquee-container {
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      background: linear-gradient(90deg, var(--primary-dark) 0%, var(--accent) 100%);
      color: white;
      padding: 0.8rem;
      font-size: 0.9rem;
      z-index: 1000;
      display: flex;
      align-items: center;
      justify-content: center;
      box-shadow: 0 4px 20px rgba(0, 0, 0, 0.2);
    }

    .marquee-container i {
      margin-right: 10px;
    }

    /* Navigation Bar */
    nav {
      background: rgba(30, 41, 59, 0.8);
      backdrop-filter: blur(15px);
      border: 1px solid rgba(99, 102, 241, 0.2);
      padding: 15px 5%;
      position: sticky;
      top: 40px;
      z-index: 1001;
      display: flex;
      align-items: center;
      justify-content: space-between;
      box-shadow: 0 5px 20px rgba(0, 0, 0, 0.1);
      border-radius: var(--border-radius);
      margin: 0 20px;
    }

    .logo {
      display: flex;
      align-items: center;
      gap: 12px;
      font-size: 1.8rem;
      font-weight: 800;
      color: var(--neutral-900);
    }

    .logo i {
      font-size: 2.2rem;
      background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
      -webkit-background-clip: text;
      -webkit-text-fill-color: transparent;
    }

    .nav-links {
      display: flex;
      gap: 25px;
    }

    .nav-links a {
      color: var(--neutral-700);
      text-decoration: none;
      font-weight: 500;
      padding: 10px 18px;
      border-radius: 12px;
      transition: var(--transition);
      position: relative;
    }

    .nav-links a:hover, .nav-links a.active {
      background: rgba(99, 102, 241, 0.1);
      color: var(--primary-light);
    }

    .nav-links a::after {
      content: '';
      position: absolute;
      bottom: 0;
      left: 50%;
      width: 0;
      height: 3px;
      background: var(--accent);
      transition: var(--transition);
      transform: translateX(-50%);
      border-radius: 3px;
    }

    .nav-links a:hover::after, .nav-links a.active::after {
      width: 70%;
    }

    .search-container {
      position: relative;
    }

    .search-icon {
      position: absolute;
      left: 15px;
      top: 50%;
      transform: translateY(-50%);
      color: var(--neutral-700);
      z-index: 2;
    }

    #search-bar {
      padding: 12px 15px 12px 45px;
      border-radius: 50px;
      border: 1px solid var(--neutral-300);
      outline: none;
      background: rgba(30, 41, 59, 0.7);
      transition: var(--transition);
      width: 280px;
      font-size: 1rem;
      box-shadow: 0 4px 10px rgba(0, 0, 0, 0.1);
      color: var(--neutral-900);
    }

    #search-bar:focus {
      border-color: var(--primary);
      box-shadow: 0 0 0 4px rgba(99, 102, 241, 0.1);
      width: 320px;
    }

    .menu-toggle {
      display: none;
      font-size: 1.6rem;
      background: none;
      border: none;
      color: var(--neutral-900);
      cursor: pointer;
    }

    /* Quiz Header - FIXED */
    .quiz-header {
      background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
      color: white;
      text-align: center;
      padding: 1.5rem 1rem;
      position: relative;
      box-shadow: 0 3px 8px rgba(37, 99, 235, 0.3);
      margin: 25px 20px;
      border-radius: var(--border-radius);
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 10px;
    }

    .quiz-header-content {
      max-width: 800px;
      width: 100%;
    }

    .quiz-header h1 {
      font-size: 2rem;
      margin-bottom: 0.5rem;
      line-height: 1.2;
      word-wrap: break-word;
    }

    .subheader {
      font-size: 1.3rem;
      font-weight: 500;
      color: rgba(255, 255, 255, 0.9);
      margin-bottom: 15px;
    }

    #dark-mode-toggle {
      background: rgba(255, 255, 255, 0.2);
      color: white;
      border: none;
      padding: 8px 15px;
      font-weight: 700;
      border-radius: 50px;
      cursor: pointer;
      transition: var(--transition);
      display: flex;
      align-items: center;
      gap: 8px;
      margin-top: 10px;
    }

    #dark-mode-toggle:hover {
      background: rgba(255, 255, 255, 0.3);
    }

    /* Quiz Container */
    #app {
      display: flex;
      max-width: 1400px;
      margin: 25px auto;
      min-height: 70vh;
      box-shadow: var(--card-shadow);
      border-radius: var(--border-radius);
      overflow: hidden;
      background: rgba(30, 41, 59, 0.7);
      backdrop-filter: blur(5px);
      border: 1px solid rgba(99, 102, 241, 0.2);
      width: calc(100% - 40px);
    }

    #sidebar {
      width: 220px;
      background: rgba(30, 41, 59, 0.8);
      padding: 20px 15px;
      display: flex;
      flex-direction: column;
      border-right: 1px solid rgba(99, 102, 241, 0.2);
    }

    #sidebar h2 {
      font-size: 1.3rem;
      font-weight: 700;
      margin-bottom: 18px;
      text-align: center;
      color: var(--primary-light);
    }

    #question-nav {
      display: flex;
      flex-wrap: wrap;
      gap: 8px;
      justify-content: center;
      overflow-y: auto;
      max-height: calc(70vh - 80px);
    }

    #question-nav button {
      width: 36px;
      height: 36px;
      border-radius: 50%;
      border: 1px solid rgba(99, 102, 241, 0.3);
      background: rgba(30, 41, 59, 0.8);
      color: var(--neutral-700);
      font-weight: 600;
      cursor: pointer;
      transition: var(--transition);
    }

    #question-nav button:hover {
      background: rgba(99, 102, 241, 0.3);
    }

    #question-nav button.answered {
      background: var(--primary);
      color: white;
      box-shadow: 0 3px 10px rgba(79, 195, 247, 0.3);
    }

    #question-nav button.current {
      transform: scale(1.1);
      border: 2px solid var(--accent);
      box-shadow: 0 0 0 3px rgba(244, 63, 94, 0.3);
    }

    #main-content {
      flex-grow: 1;
      display: flex;
      flex-direction: column;
      padding: 30px 40px;
      position: relative;
    }

    #timer {
      align-self: flex-end;
      font-weight: 700;
      font-size: 1.15rem;
      color: var(--primary-light);
      font-variant-numeric: tabular-nums;
      margin-bottom: 20px;
      padding: 8px 15px;
      background: rgba(99, 102, 241, 0.2);
      border-radius: 50px;
    }

    #quiz-container {
      flex-grow: 1;
      display: flex;
      flex-direction: column;
    }

    #question-number {
      font-weight: 600;
      font-size: 1.1rem;
      margin-bottom: 10px;
      color: var(--primary-light);
    }

    #question-text {
      font-size: 1.2rem;
      margin-bottom: 25px;
      line-height: 1.5;
      padding: 15px;
      background: rgba(30, 41, 59, 0.5);
      border-radius: var(--border-radius);
      box-shadow: var(--card-shadow);
      border: 1px solid rgba(99, 102, 241, 0.2);
    }

    #options-container {
      display: flex;
      flex-direction: column;
      gap: 12px;
      margin-bottom: 25px;
    }

    .option {
      background: rgba(30, 41, 59, 0.5);
      border: 1px solid rgba(99, 102, 241, 0.2);
      border-radius: var(--border-radius);
      padding: 15px 20px;
      cursor: pointer;
      font-weight: 500;
      transition: var(--transition);
      box-shadow: var(--card-shadow);
      position: relative;
    }

    .option:hover,
    .option:focus {
      border-color: var(--primary);
      background-color: rgba(99, 102, 241, 0.2);
      transform: translateY(-2px);
    }

    .option.selected {
      background-color: var(--primary);
      color: white;
      border-color: var(--primary-dark);
      box-shadow: 0 5px 15px rgba(79, 195, 247, 0.4);
    }

    .key-badge {
      position: absolute;
      right: 10px;
      top: 50%;
      transform: translateY(-50%);
      background: var(--primary);
      color: white;
      width: 24px;
      height: 24px;
      border-radius: 50%;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 0.8rem;
      font-weight: bold;
    }

    .option.selected .key-badge {
      background: white;
      color: var(--primary);
    }

    #navigation {
      display: flex;
      justify-content: space-between;
      align-items: center;
      gap: 15px;
      margin-top: auto;
    }

    #navigation button {
      padding: 12px 24px;
      font-weight: 700;
      font-size: 1rem;
      border-radius: 50px;
      border: none;
      cursor: pointer;
      transition: var(--transition);
      background-color: var(--primary);
      color: white;
      box-shadow: var(--card-shadow);
    }

    #navigation button:hover:not(:disabled) {
      background-color: var(--primary-dark);
      transform: translateY(-2px);
    }

    #navigation button:disabled {
      background-color: var(--neutral-700);
      cursor: not-allowed;
      opacity: 0.7;
    }

    #submit-btn {
      min-width: 120px;
      background: var(--accent) !important;
    }

    #submit-btn:hover:not(:disabled) {
      background: var(--accent-dark) !important;
    }

    #result-container {
      flex-grow: 1;
      padding: 20px;
      display: flex;
      flex-direction: column;
      gap: 15px;
      background: rgba(30, 41, 59, 0.5);
      border-radius: var(--border-radius);
      box-shadow: var(--card-shadow);
      border: 1px solid rgba(99, 102, 241, 0.2);
    }

    #result-container h2 {
      color: var(--primary-light);
      text-align: center;
      margin-bottom: 15px;
      font-size: 1.8rem;
    }

    #score {
      font-size: 1.5rem;
      font-weight: 700;
      text-align: center;
      margin-bottom: 20px;
      padding: 15px;
      background: rgba(16, 185, 129, 0.15);
      border-radius: var(--border-radius);
    }

    .result-question {
      border: 1px solid rgba(99, 102, 241, 0.2);
      border-radius: var(--border-radius);
      padding: 15px;
      background: rgba(30, 41, 59, 0.5);
      margin-bottom: 10px;
    }

    .correct {
      color: var(--success);
      font-weight: 700;
    }

    .wrong {
      color: var(--accent);
      font-weight: 700;
    }

    #retry-btn {
      align-self: center;
      padding: 12px 30px;
      font-weight: 700;
      font-size: 1.1rem;
      border-radius: 50px;
      border: none;
      cursor: pointer;
      background-color: var(--primary);
      color: white;
      margin-top: 20px;
      transition: var(--transition);
    }

    #retry-btn:hover {
      background-color: var(--primary-dark);
      transform: translateY(-2px);
    }

    /* Start Screen - FIXED */
    #start-screen {
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: flex-start;
      min-height: 70vh;
      max-width: 800px;
      margin: 40px auto;
      padding: 40px 30px;
      background: rgba(30, 41, 59, 0.7);
      border-radius: var(--border-radius);
      box-shadow: var(--card-shadow);
      border: 1px solid rgba(99, 102, 241, 0.2);
      text-align: center;
    }

    #start-screen h1 {
      font-size: 2.2rem;
      margin-bottom: 20px;
      color: var(--primary-light);
      line-height: 1.2;
    }

    #start-screen p {
      font-size: 1.1rem;
      color: var(--neutral-700);
      max-width: 600px;
      margin-bottom: 30px;
      line-height: 1.6;
    }

    .keyboard-shortcuts {
      background: rgba(99, 102, 241, 0.2);
      border-radius: var(--border-radius);
      padding: 20px;
      margin-top: 20px;
      width: 100%;
      max-width: 500px;
    }

    .keyboard-shortcuts h3 {
      color: var(--primary-light);
      margin-bottom: 15px;
    }

    .shortcut-row {
      display: flex;
      justify-content: space-between;
      padding: 8px 0;
      border-bottom: 1px solid rgba(99, 102, 241, 0.2);
    }

    .key {
      background: var(--primary);
      color: white;
      padding: 3px 8px;
      border-radius: 4px;
      font-weight: bold;
    }

    /* Question count selector styles */
    .question-count-selector {
      background: rgba(99, 102, 241, 0.2);
      border-radius: var(--border-radius);
      padding: 20px;
      margin: 20px 0;
      width: 100%;
      max-width: 500px;
      display: flex;
      flex-direction: column;
      align-items: center;
    }

    .question-count-selector h3 {
      color: var(--primary-light);
      margin-bottom: 15px;
    }

    .count-input-container {
      display: flex;
      align-items: center;
      gap: 15px;
      margin-bottom: 15px;
    }

    .count-input {
      display: flex;
      align-items: center;
      background: rgba(30, 41, 59, 0.8);
      border-radius: 50px;
      padding: 5px;
      border: 1px solid rgba(99, 102, 241, 0.3);
    }

    .count-btn {
      width: 36px;
      height: 36px;
      border-radius: 50%;
      background: var(--primary);
      color: white;
      border: none;
      font-size: 1.2rem;
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: center;
      transition: var(--transition);
    }

    .count-btn:hover {
      background: var(--primary-dark);
    }

    #question-count {
      width: 60px;
      text-align: center;
      background: transparent;
      border: none;
      color: var(--neutral-900);
      font-size: 1.2rem;
      font-weight: 600;
      margin: 0 5px;
    }

    input[type=number]::-webkit-inner-spin-button, 
    input[type=number]::-webkit-outer-spin-button { 
      -webkit-appearance: none; 
      margin: 0; 
    }

    .count-slider {
      width: 100%;
      margin: 15px 0;
    }

    .count-slider input {
      width: 100%;
      height: 8px;
      -webkit-appearance: none;
      appearance: none;
      background: linear-gradient(to right, var(--primary), var(--accent));
      outline: none;
      border-radius: 4px;
    }

    .count-slider input::-webkit-slider-thumb {
      -webkit-appearance: none;
      appearance: none;
      width: 22px;
      height: 22px;
      border-radius: 50%;
      background: var(--primary-light);
      cursor: pointer;
      border: 2px solid var(--primary);
      box-shadow: 0 0 5px rgba(0, 0, 0, 0.2);
    }

    .count-value {
      font-weight: 600;
      color: var(--primary-light);
      margin-top: 5px;
    }

    .time-estimate {
      font-weight: 600;
      color: var(--primary-light);
      margin-top: 10px;
      font-size: 1.1rem;
    }

    #start-quiz-btn {
      padding: 15px 40px;
      font-size: 1.2rem;
      font-weight: 700;
      color: white;
      background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
      border: none;
      border-radius: 50px;
      cursor: pointer;
      transition: var(--transition);
      box-shadow: var(--card-shadow);
      margin-top: 20px;
    }

    #start-quiz-btn:hover {
      transform: translateY(-3px);
      box-shadow: 0 8px 20px rgba(99, 102, 241, 0.4);
    }

    /* Reload confirmation dialog */
    #reload-confirm {
      display: none;
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      background: rgba(0,0,0,0.7);
      color: white;
      font-size: 1.3rem;
      align-items: center;
      justify-content: center;
      z-index: 9999;
      flex-direction: column;
      backdrop-filter: blur(3px);
    }

    #reload-confirm .reload-content {
      background: rgba(30, 41, 59, 0.95);
      padding: 30px;
      border-radius: var(--border-radius);
      text-align: center;
      max-width: 500px;
      width: 90%;
      box-shadow: var(--card-shadow);
      border: 1px solid rgba(99, 102, 241, 0.3);
    }

    #reload-confirm h3 {
      color: var(--primary-light);
      margin-bottom: 20px;
      font-size: 1.8rem;
    }

    #reload-confirm p {
      margin-bottom: 30px;
      line-height: 1.6;
    }

    #reload-confirm .reload-buttons {
      display: flex;
      justify-content: center;
      gap: 15px;
    }

    #reload-confirm button {
      padding: 12px 30px;
      font-size: 1.1rem;
      border-radius: 50px;
      border: none;
      cursor: pointer;
      transition: var(--transition);
    }

    #reload-submit {
      background: var(--primary);
      color: white;
    }

    #reload-submit:hover {
      background: var(--primary-dark);
    }

    #reload-cancel {
      background: var(--accent);
      color: white;
    }

    #reload-cancel:hover {
      background: var(--accent-dark);
    }

    #customConfirm {
      display: none;
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      background: rgba(0,0,0,0.7);
      color: white;
      font-size: 1.3rem;
      align-items: center;
      justify-content: center;
      z-index: 9999;
      flex-direction: column;
      backdrop-filter: blur(3px);
    }

    #customConfirm p {
      margin-bottom: 30px;
      text-align: center;
      max-width: 500px;
      line-height: 1.6;
    }

    #customConfirm div {
      display: flex;
      gap: 15px;
    }

    #customConfirm button {
      padding: 12px 30px;
      font-size: 1.1rem;
      border-radius: 50px;
      border: none;
      cursor: pointer;
      transition: var(--transition);
    }

    #confirmYes {
      background: var(--primary);
      color: white;
    }

    #confirmYes:hover {
      background: var(--primary-dark);
    }

    #confirmNo {
      background: var(--accent);
      color: white;
    }

    #confirmNo:hover {
      background: var(--accent-dark);
    }

    /* KaTeX-specific styles */
    .katex {
      font-size: 1.1em !important;
      padding: 0 2px;
    }

    /* Animations */
    @keyframes float {
      0%, 100% { transform: translateY(0) rotate(0deg); }
      33% { transform: translateY(-20px) rotate(3deg); }
      66% { transform: translateY(10px) rotate(-3deg); }
    }

    /* Responsive Design - IMPROVED */
    @media (max-width: 1200px) {
      #search-bar:focus {
        width: 280px;
      }
    }

    @media (max-width: 992px) {
      .quiz-header {
        flex-direction: column;
        text-align: center;
        padding: 1.2rem 0.8rem;
      }
      
      .quiz-header h1 {
        font-size: 1.8rem;
      }
      
      .subheader {
        font-size: 1.1rem;
      }
    }

    @media (max-width: 768px) {
      body {
        padding-top: 40px;
      }
      
      nav {
        top: 35px;
        flex-wrap: wrap;
        padding: 15px;
        margin: 0 10px;
      }
      
      .nav-links {
        flex-direction: column;
        width: 100%;
        display: none;
        background: rgba(30, 41, 59, 0.95);
        padding: 20px 0;
        margin-top: 15px;
        gap: 15px;
      }

      .nav-links.show {
        display: flex;
      }

      .menu-toggle {
        display: block;
      }

      #search-bar {
        margin: 15px 0;
        width: 100%;
        order: 1;
      }

      .marquee-container {
        font-size: 0.8rem;
        padding: 0.6rem;
      }

      #sidebar {
        display: none;
      }
      
      .quiz-header {
        margin: 20px 10px;
        padding: 1rem 0.5rem;
      }
      
      .quiz-header h1 {
        font-size: 1.6rem;
        padding: 0 10px;
      }
      
      .subheader {
        font-size: 1rem;
        padding: 0 10px;
      }
      
      #main-content {
        padding: 20px;
      }
      
      #question-text {
        font-size: 1.1rem;
      }
      
      #navigation {
        flex-direction: column;
      }
      
      #navigation button {
        width: 100%;
      }

      .question-count-selector {
        padding: 15px;
      }

      .count-input-container {
        flex-direction: column;
        gap: 10px;
      }

      #reload-confirm .reload-content {
        padding: 20px;
      }

      #reload-confirm h3 {
        font-size: 1.5rem;
      }

      #reload-confirm p {
        font-size: 1.1rem;
      }

      #reload-confirm .reload-buttons {
        flex-direction: column;
      }

      #reload-confirm button {
        width: 100%;
      }

      #start-screen {
        padding: 30px 20px;
        margin: 30px 15px;
      }

      #start-screen h1 {
        font-size: 1.9rem;
      }

      #start-screen p {
        font-size: 1rem;
      }
    }

    @media (max-width: 480px) {
      .quiz-header {
        margin: 15px 8px;
        padding: 0.8rem 0.3rem;
      }
      
      .quiz-header h1 {
        font-size: 1.4rem;
      }
      
      .subheader {
        font-size: 0.9rem;
      }
      
      #timer {
        font-size: 1rem;
      }
      
      #question-text {
        padding: 10px;
        font-size: 1rem;
      }
      
      .option {
        padding: 12px 15px;
      }
      
      .key-badge {
        display: none;
      }
      
      body {
        padding-top: 130px;
      }

      #start-screen {
        padding: 25px 15px;
        margin: 20px 10px;
      }

      #start-screen h1 {
        font-size: 1.7rem;
      }

      .logo {
        font-size: 1.5rem;
      }
      
      .logo i {
        font-size: 1.8rem;
      }
    }

/* Overlay screen */
#overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: #0a0a0a;
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: "Inter", sans-serif;
  font-size: 1.5rem;
  z-index: 9999;
  transition: opacity 0.6s ease;
}

/* Hide after fade */
#overlay.hidden {
  opacity: 0;
  pointer-events: none;
}