/* 1. CSS Reset & Base Styles */
    
    * {
        margin: 0;
        padding: 0;
        box-sizing: border-box;
    }
    /* 2. Root Variables - Enhanced color scheme */
    
     :root {
        /* Base Colors */
        --bg-gradient-start: linear-gradient(135deg, #03fed0, #0230ff);
        --bg-gradient-end: linear-gradient(135deg, #0a0a1a, #1a1a2e);
        /* Semantic Colors */
        --primary: #01d6af;
        --primary-dark: #01a58b;
        --primary-light: #34e5c8;
        --secondary: #0a33ec;
        --secondary-dark: #0826b8;
        --secondary-light: #3c66f3;
        --accent: #ff4081;
        --success: #4caf50;
        --success-dark: #388e3c;
        --warning: #ff9800;
        --warning-dark: #f57c00;
        --danger: #f44336;
        --danger-dark: #d32f2f;
        --info: #2196f3;
        --info-dark: #1976d2;
        --light: #f8f9fa;
        --dark: #343a40;
        --text-primary: #222;
        --text-secondary: #666;
        --text-light: #e0e0e0;
        --text-lighter: #f5f5f5;
        --text-dark: #121212;
        --card-bg: rgba(255, 255, 255, 0.95);
        --card-bg-dark: rgba(30, 30, 40, 0.95);
        --card-bg-light: rgba(255, 255, 255, 0.85);
        --card-bg-lighter: rgba(255, 255, 255, 0.7);
        --border-radius: 12px;
        --border-radius-sm: 8px;
        --border-radius-lg: 16px;
        --box-shadow: 0 8px 30px rgba(0, 0, 0, 0.12);
        --box-shadow-sm: 0 4px 15px rgba(0, 0, 0, 0.1);
        --box-shadow-lg: 0 15px 35px rgba(1, 214, 175, 0.2);
        --box-shadow-hover: 0 15px 35px rgba(1, 214, 175, 0.25);
        --transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
        --transition-fast: all 0.15s ease;
        --transition-slow: all 0.5s cubic-bezier(0.25, 0.8, 0.25, 1);
        --font-family: 'Segoe UI', system-ui, -apple-system, 'Roboto', sans-serif;
        --font-size-sm: 0.875rem;
        --font-size-base: 1rem;
        --font-size-lg: 1.125rem;
        --font-size-xl: 1.25rem;
        --font-size-2xl: 1.5rem;
        --font-size-3xl: 1.875rem;
        --font-size-4xl: 2.25rem;
        --font-weight-normal: 400;
        --font-weight-medium: 500;
        --font-weight-semibold: 600;
        --font-weight-bold: 700;
    }
    /* 3. Base Styles */
    
    body {
        font-family: var(--font-family);
        background: var(--bg-gradient-start);
        min-height: 100vh;
        margin: 0;
        color: var(--text-primary);
        transition: background var(--transition-slow);
        line-height: 1.6;
    }
    /* 4. Enhanced App Container */
    
    .app-container {
        max-width: 800px;
        margin: 2rem auto;
        padding: 2rem;
        border-radius: var(--border-radius);
        box-shadow: var(--box-shadow);
        position: relative;
        background: var(--card-bg);
        backdrop-filter: blur(10px);
        animation: float 6s ease-in-out infinite;
        border: 1px solid rgba(255, 255, 255, 0.2);
        overflow: hidden;
        transition: var(--transition);
        z-index: 1;
    }
    
    .app-container::before {
        content: '';
        position: absolute;
        top: -50%;
        left: -50%;
        width: 200%;
        height: 200%;
        background: radial-gradient(circle, rgba(255, 255, 255, 0.1) 0%, transparent 70%);
        z-index: -1;
        animation: rotate 20s linear infinite;
    }
    /* 5. Screen Management */
    
    .screen {
        display: none;
        opacity: 0;
        transform: translateY(20px);
        transition: opacity 0.4s ease, transform 0.4s ease;
    }
    
    .screen.active {
        display: block;
        opacity: 1;
        transform: translateY(0);
        animation: fadeInUp 0.4s ease-out;
    }
    /* 6. Main Menu Screen */
    
    #main-menu {
        text-align: center;
        padding: 2rem 0;
        position: relative;
    }
    
    #main-menu::before {
        content: '';
        position: absolute;
        top: -10px;
        left: 50%;
        transform: translateX(-50%);
        width: 80px;
        height: 80px;
        background: var(--primary);
        border-radius: 50%;
        opacity: 0.1;
        z-index: -1;
    }
    
    #main-menu h1 {
        font-size: var(--font-size-4xl);
        margin-bottom: 1rem;
        text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.1);
        position: relative;
        display: inline-block;
        animation: glow 2s ease-in-out infinite alternate;
        font-weight: var(--font-weight-bold);
    }
    
    #main-menu h1::after {
        content: '';
        position: absolute;
        bottom: -10px;
        left: 50%;
        transform: translateX(-50%);
        width: 100px;
        height: 4px;
        background: linear-gradient(to right, var(--primary), var(--secondary));
        border-radius: 2px;
    }
    
    #main-menu p {
        font-size: var(--font-size-lg);
        margin-bottom: 2rem;
        color: var(--text-secondary);
    }
    /* 7. Enhanced Button Styles */
    
    .btn {
        padding: 0.8rem 2rem;
        font-size: var(--font-size-base);
        border: none;
        border-radius: var(--border-radius-sm);
        cursor: pointer;
        margin: 0.5rem;
        transition: var(--transition);
        font-weight: var(--font-weight-semibold);
        text-transform: uppercase;
        letter-spacing: 0.5px;
        box-shadow: var(--box-shadow-sm);
        position: relative;
        overflow: hidden;
        z-index: 1;
        display: inline-flex;
        align-items: center;
        justify-content: center;
        text-decoration: none;
        min-width: 180px;
        min-height: 50px;
        border: none;
    }
    
    .btn::before {
        content: '';
        position: absolute;
        top: 0;
        left: -100%;
        width: 100%;
        height: 100%;
        background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
        transition: 0.5s;
        z-index: -1;
    }
    
    .btn:hover::before {
        left: 100%;
    }
    
    .btn:hover {
        transform: translateY(-3px);
        box-shadow: var(--box-shadow-hover);
    }
    
    .btn:active {
        transform: translateY(1px);
    }
    
    .btn:disabled {
        opacity: 0.6;
        cursor: not-allowed;
        transform: none;
        pointer-events: none;
    }
    
    .btn:focus {
        outline: 2px solid var(--primary);
        outline-offset: 2px;
    }
    
    .btn-large {
        padding: 1.2rem;
        font-size: var(--font-size-lg);
        margin: 1rem 0;
        border-radius: var(--border-radius);
        width: 100%;
        text-transform: uppercase;
        letter-spacing: 1px;
        box-shadow: var(--box-shadow);
        min-height: 60px;
    }
    
    .btn-primary {
        background: linear-gradient(135deg, var(--primary), var(--secondary));
        color: white;
    }
    
    .btn-primary:hover {
        background: linear-gradient(135deg, var(--primary-dark), var(--secondary-dark));
    }
    
    .btn-secondary {
        background: linear-gradient(135deg, var(--secondary), #4a148c);
        color: white;
    }
    
    .btn-secondary:hover {
        background: linear-gradient(135deg, var(--secondary-dark), #380e6d);
    }
    
    .btn-success {
        background: linear-gradient(135deg, var(--success), var(--success-dark));
        color: white;
    }
    
    .btn-success:hover {
        background: linear-gradient(135deg, var(--success-dark), #1b5e20);
    }
    
    .btn-warning {
        background: linear-gradient(135deg, var(--warning), var(--warning-dark));
        color: white;
    }
    
    .btn-warning:hover {
        background: linear-gradient(135deg, var(--warning-dark), #e65100);
    }
    
    .btn-danger {
        background: linear-gradient(135deg, var(--danger), var(--danger-dark));
        color: white;
    }
    
    .btn-danger:hover {
        background: linear-gradient(135deg, var(--danger-dark), #b71c1c);
    }
    /* 8. Subject Grid */
    
    .subject-grid {
        display: grid;
        grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
        gap: 1.5rem;
        margin: 2.5rem 0;
    }
    
    .subject-btn {
        padding: 24px;
        font-size: var(--font-size-lg);
        font-weight: var(--font-weight-semibold);
        background: var(--secondary-dark);
        color: white;
        border: none;
        border-radius: var(--border-radius);
        cursor: pointer;
        transition: var(--transition);
        box-shadow: var(--box-shadow-sm);
        display: flex;
        flex-direction: column;
        align-items: center;
        justify-content: center;
        gap: 0.5rem;
        position: relative;
        overflow: hidden;
        z-index: 1;
        text-align: center;
    }
    
    .subject-btn::before {
        content: '';
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
        background: linear-gradient(45deg, #ff8a00, #e52e71, #00c3ff);
        z-index: -1;
        opacity: 0;
        transition: opacity 0.3s ease;
    }
    #back-to-menu-btn{
        background: var(--secondary-light);
        color: white;
    }
    #start-btn{
        background: var(--success-dark);
        color: white;
    }
    #back-from-instructions{
        background: var(--secondary-light);
        color: white;
    }
    #admin-submit-quiz-btn{
        background: var(--success);
        color: white;
    }
    #back-from-admin-btn{
        background: var(--secondary);
        color: white;
    }
    #next-btn{
        background: var(--secondary-light);
        color: white;
    }
    #restart-btn{
        background: var(--secondary-light);
        color: white;
    }
    .subject-btn:hover::before {
        opacity: 0.3;
    }
    #admin-add-question-btn{
        background: var(--secondary-light);
        color: white;
    }
    #choose-subject-btn{
        background: var(--success-dark);
        color: white;
    }
    #admin-quiz-btn{
        background: var(--secondary-light);
        color: white;
    }
    .subject-btn:hover {
        transform: scale(1.05) translateY(-5px);
        box-shadow: var(--box-shadow-lg);
        /* background: linear-gradient(135deg, var(--primary-dark), var(--secondary-dark)); */
    }
    
    .subject-btn:active {
        transform: scale(0.98);
    }
    
    .subject-btn:focus {
        outline: 2px solid var(--primary-light);
        outline-offset: 2px;
    }
    /* 9. Input Fields */
    
    .input-field {
        width: 100%;
        padding: 0.9rem;
        margin: 1.2rem 0;
        border: 2px solid #ddd;
        border-radius: var(--border-radius-sm);
        font-size: var(--font-size-base);
        box-sizing: border-box;
        transition: var(--transition);
        background: white;
        position: relative;
        outline: none;
    }
    
    .input-field:focus {
        border-color: var(--primary);
        box-shadow: 0 0 0 3px rgba(1, 214, 175, 0.3);
    }
    
    .input-field::placeholder {
        color: #aaa;
    }
    /* 10. Quiz Header */
    
    .quiz-header {
        display: flex;
        justify-content: space-between;
        align-items: center;
        margin-bottom: 1rem;
        padding: 1rem;
        background: var(--card-bg-light);
        border-radius: var(--border-radius);
        position: relative;
        overflow: hidden;
        z-index: 1;
        box-shadow: var(--box-shadow-sm);
        flex-wrap: wrap;
        gap: 1rem;
    }
    
    .quiz-header::before {
        content: '';
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
        background: linear-gradient(90deg, rgba(1, 214, 175, 0.1), rgba(10, 51, 236, 0.1));
        z-index: -1;
    }
    
    #current-subject {
        color: var(--primary);
        font-weight: var(--font-weight-bold);
        margin: 0;
        font-size: var(--font-size-lg);
    }
    
    #question-title {
        font-size: var(--font-size-xl);
        margin: 1rem 0;
        color: var(--text-primary);
        text-align: center;
        line-height: 1.4;
        flex-basis: 100%;
    }
    
    #timer {
        font-size: var(--font-size-lg);
        font-weight: var(--font-weight-bold);
        background: linear-gradient(135deg, var(--danger), #e91e63);
        color: white;
        padding: 0.5rem 1rem;
        border-radius: 20px;
        display: inline-flex;
        align-items: center;
        gap: 0.5rem;
        box-shadow: 0 4px 12px rgba(244, 67, 54, 0.3);
        animation: pulse 1.5s infinite;
        min-width: 120px;
        justify-content: center;
    }
    /* 11. Enhanced Progress Bar */
    
    .progress-bar-container {
        background: #e0e0e0;
        border-radius: 10px;
        overflow: hidden;
        height: 20px;
        margin-bottom: 1.5rem;
        position: relative;
        box-shadow: inset 0 1px 2px rgba(0, 0, 0, 0.1);
        border: 1px solid rgba(0, 0, 0, 0.05);
    }
    
    .progress-bar {
        height: 100%;
        background: linear-gradient(90deg, var(--primary), var(--secondary));
        text-align: center;
        color: white;
        font-size: 0.8rem;
        font-weight: var(--font-weight-bold);
        width: 0%;
        transition: width 0.4s ease;
        display: flex;
        align-items: center;
        justify-content: center;
        position: relative;
        overflow: hidden;
        min-width: 40px;
        animation: progressFill 0.5s ease-out;
    }
    
    .progress-bar::after {
        content: '';
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
        background: linear-gradient(45deg, rgba(255, 255, 255, 0.3) 25%, transparent 25%, transparent 50%, rgba(255, 255, 255, 0.3) 50%, rgba(255, 255, 255, 0.3) 75%, transparent 75%);
        background-size: 30px 30px;
        animation: progressAnimation 1s linear infinite;
        z-index: 1;
    }
    /* 12. Question Counter */
    
    .question-counter {
        text-align: center;
        font-size: var(--font-size-lg);
        font-weight: var(--font-weight-semibold);
        margin: 1rem 0;
        color: var(--text-primary);
        background: rgba(33, 150, 243, 0.1);
        padding: 0.75rem;
        border-radius: var(--border-radius-sm);
        display: inline-block;
        min-width: 180px;
        margin-left: auto;
        margin-right: auto;
        border: 1px solid rgba(33, 150, 243, 0.2);
    }
    
    .question-counter span {
        color: var(--primary);
        font-weight: var(--font-weight-bold);
        font-size: var(--font-size-xl);
    }
    /* 13. Answer Options */
    
    #quiz-form label {
        display: block;
        margin: 0.8rem 0;
        padding: 1.2rem;
        border-radius: var(--border-radius-sm);
        background: white;
        border: 2px solid #e9ecef;
        transition: var(--transition);
        font-size: var(--font-size-base);
        cursor: pointer;
        display: flex;
        align-items: center;
        gap: 0.75rem;
        position: relative;
        overflow: hidden;
        box-shadow: var(--box-shadow-sm);
        animation: fadeIn 0.3s ease-out;
    }
    
    #quiz-form label::before {
        content: '';
        position: absolute;
        top: 0;
        left: -100%;
        width: 100%;
        height: 100%;
        background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
        transition: 0.5s;
        z-index: -1;
    }
    
    #quiz-form label:hover::before {
        left: 100%;
    }
    
    #quiz-form label:hover {
        /* background: #f8f9fa; */
        border-color: var(--primary);
        transform: translateX(5px);
        box-shadow: 0 5px 15px rgba(1, 214, 175, 0.1);
    }
    
    #quiz-form label input[type="radio"],
    #quiz-form label input[type="checkbox"] {
        margin-right: 0.75rem;
        transform: scale(1.2);
        accent-color: var(--primary);
        cursor: pointer;
    }
    
    #quiz-form label.correct {
        border-color: var(--success);
        background: rgba(76, 175, 80, 0.1);
        animation: correctAnswer 0.5s ease;
    }
    
    #quiz-form label.incorrect {
        border-color: var(--danger);
        background: rgba(244, 67, 54, 0.1);
        animation: incorrectAnswer 0.5s ease;
    }
    /* 14. Result Screen */
    
    #result {
        text-align: center;
        padding: 2rem 0;
        position: relative;
    }
    
    #result h2 {
        font-size: var(--font-size-3xl);
        color: var(--success);
        margin-bottom: 1.5rem;
        position: relative;
        animation: glow 2s ease-in-out infinite alternate;
        font-weight: var(--font-weight-bold);
    }
    
    #result h2::after {
        content: '';
        position: absolute;
        bottom: -10px;
        left: 50%;
        transform: translateX(-50%);
        width: 100px;
        height: 4px;
        background: linear-gradient(to right, var(--success), var(--primary));
        border-radius: 2px;
    }
    
    #final-score {
        font-size: var(--font-size-3xl);
        font-weight: var(--font-weight-bold);
        margin: 1.5rem 0;
        color: var(--text-primary);
        background: linear-gradient(to right, var(--primary), var(--secondary));
        -webkit-background-clip: text;
        background-clip: text;
        color: transparent;
        font-weight: var(--font-weight-bold);
        font-size: 3rem;
    }
    
    #celebration-message {
        font-size: var(--font-size-xl);
        color: var(--success);
        margin: 1.5rem 0;
        font-weight: var(--font-weight-bold);
        animation: float 3s ease-in-out infinite;
    }
    /* 15. Animations */
    
    @keyframes float {
        0% {
            transform: translateY(0px);
        }
        50% {
            transform: translateY(-10px);
        }
        100% {
            transform: translateY(0px);
        }
    }
    
    @keyframes pulse {
        0% {
            transform: scale(1);
            box-shadow: 0 0 0 0 rgba(244, 67, 54, 0.4);
        }
        50% {
            transform: scale(1.05);
            box-shadow: 0 0 0 10px rgba(244, 67, 54, 0);
        }
        100% {
            transform: scale(1);
            box-shadow: 0 0 0 0 rgba(244, 67, 54, 0);
        }
    }
    
    @keyframes glow {
        from {
            text-shadow: 0 0 5px rgba(1, 214, 175, 0.5);
        }
        to {
            text-shadow: 0 0 20px rgba(1, 214, 175, 0.8), 0 0 30px rgba(1, 214, 175, 0.6);
        }
    }
    
    @keyframes rotate {
        0% {
            transform: rotate(0deg);
        }
        100% {
            transform: rotate(360deg);
        }
    }
    
    @keyframes fadeIn {
        from {
            opacity: 0;
        }
        to {
            opacity: 1;
        }
    }
    
    @keyframes fadeInUp {
        from {
            opacity: 0;
            transform: translateY(20px);
        }
        to {
            opacity: 1;
            transform: translateY(0);
        }
    }
    
    @keyframes progressAnimation {
        0% {
            background-position: 0 0;
        }
        100% {
            background-position: 30px 30px;
        }
    }
    
    @keyframes correctAnswer {
        0% {
            transform: scale(1);
            border-color: var(--success);
        }
        50% {
            transform: scale(1.02);
            border-color: var(--success-dark);
        }
        100% {
            transform: scale(1);
            border-color: var(--success);
        }
    }
    
    @keyframes incorrectAnswer {
        0% {
            transform: scale(1);
            border-color: var(--danger);
        }
        25% {
            transform: scale(0.95);
            border-color: var(--danger-dark);
        }
        50% {
            transform: scale(1.05);
            border-color: var(--danger-dark);
        }
        75% {
            transform: scale(0.95);
            border-color: var(--danger-dark);
        }
        100% {
            transform: scale(1);
            border-color: var(--danger);
        }
    }
    
    @keyframes progressFill {
        from {
            width: 0%;
        }
    }
    /* 16. Utility Classes */
    
    .text-center {
        text-align: center;
    }
    
    .text-primary {
        color: var(--primary);
    }
    
    .text-secondary {
        color: var(--secondary);
    }
    
    .text-success {
        color: var(--success);
    }
    
    .text-danger {
        color: var(--danger);
    }
    
    .text-warning {
        color: var(--warning);
    }
    
    .bg-primary {
        background: var(--primary);
    }
    
    .bg-secondary {
        background: var(--secondary);
    }
    
    .bg-success {
        background: var(--success);
    }
    
    .bg-danger {
        background: var(--danger);
    }
    
    .bg-warning {
        background: var(--warning);
    }
    
    .mt-1 {
        margin-top: 0.25rem;
    }
    
    .mt-2 {
        margin-top: 0.5rem;
    }
    
    .mt-3 {
        margin-top: 1rem;
    }
    
    .mt-4 {
        margin-top: 1.5rem;
    }
    
    .mt-5 {
        margin-top: 3rem;
    }
    
    .mb-1 {
        margin-bottom: 0.25rem;
    }
    
    .mb-2 {
        margin-bottom: 0.5rem;
    }
    
    .mb-3 {
        margin-bottom: 1rem;
    }
    
    .mb-4 {
        margin-bottom: 1.5rem;
    }
    
    .mb-5 {
        margin-bottom: 3rem;
    }
    
    .p-1 {
        padding: 0.25rem;
    }
    
    .p-2 {
        padding: 0.5rem;
    }
    
    .p-3 {
        padding: 1rem;
    }
    
    .p-4 {
        padding: 1.5rem;
    }
    
    .p-5 {
        padding: 3rem;
    }
    
    .d-flex {
        display: flex;
    }
    
    .d-block {
        display: block;
    }
    
    .d-inline {
        display: inline;
    }
    
    .d-inline-block {
        display: inline-block;
    }
    
    .justify-content-center {
        justify-content: center;
    }
    
    .justify-content-between {
        justify-content: space-between;
    }
    
    .align-items-center {
        align-items: center;
    }
    
    .w-100 {
        width: 100%;
    }
    
    .h-100 {
        height: 100%;
    }
    
    .rounded {
        border-radius: var(--border-radius);
    }
    
    .rounded-sm {
        border-radius: var(--border-radius-sm);
    }
    
    .rounded-lg {
        border-radius: var(--border-radius-lg);
    }
    
    .shadow {
        box-shadow: var(--box-shadow);
    }
    
    .shadow-sm {
        box-shadow: var(--box-shadow-sm);
    }
    
    .shadow-lg {
        box-shadow: var(--box-shadow-lg);
    }
    /* 17. Responsive Design */
    
    @media (max-width: 992px) {
        .app-container {
            padding: 1.8rem;
            margin: 1.5rem;
        }
        #main-menu h1 {
            font-size: calc(var(--font-size-4xl) * 0.9);
        }
        .subject-grid {
            grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
            gap: 1.2rem;
        }
        .subject-btn {
            padding: 2rem 1.5rem;
            font-size: var(--font-size-base);
            min-height: 160px;
        }
        #question-title {
            font-size: var(--font-size-lg);
        }
        #final-score {
            font-size: 2.5rem;
        }
    }
    
    @media (max-width: 768px) {
        .app-container {
            padding: 1.5rem;
            margin: 1rem;
        }
        #main-menu h1 {
            font-size: var(--font-size-3xl);
        }
        .subject-grid {
            grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
            gap: 1rem;
        }
        .subject-btn {
            padding: 1.8rem 1rem;
            font-size: var(--font-size-base);
            min-height: 140px;
        }
        .btn-large {
            padding: 1rem;
            font-size: var(--font-size-base);
        }
        .quiz-header {
            flex-direction: column;
            gap: 1rem;
            text-align: center;
        }
        #question-title {
            font-size: var(--font-size-lg);
        }
        #timer {
            align-self: center;
        }
        #result h2 {
            font-size: var(--font-size-2xl);
        }
        #final-score {
            font-size: 2.2rem;
        }
        .question-counter {
            min-width: 140px;
            padding: 0.5rem;
        }
    }
    
    @media (max-width: 576px) {
        .app-container {
            padding: 1.2rem;
            margin: 0.8rem;
        }
        #main-menu h1 {
            font-size: var(--font-size-2xl);
        }
        .subject-grid {
            grid-template-columns: 1fr;
        }
        .subject-btn {
            min-height: 120px;
            padding: 1.5rem 1rem;
        }
        .btn {
            min-width: 140px;
            margin: 0.3rem;
            padding: 0.7rem 1.5rem;
            font-size: var(--font-size-sm);
            min-height: 45px;
        }
        #question-title {
            font-size: var(--font-size-base);
        }
        #final-score {
            font-size: 1.8rem;
        }
        #result h2 {
            font-size: var(--font-size-xl);
        }
        .question-counter {
            min-width: 120px;
            font-size: var(--font-size-base);
        }
        .question-counter span {
            font-size: var(--font-size-lg);
        }
    }
    
    @media (max-width: 480px) {
        .app-container {
            padding: 1rem;
            margin: 0.5rem;
        }
        #main-menu h1 {
            font-size: calc(var(--font-size-2xl) * 0.9);
        }
        .btn {
            min-width: 120px;
            padding: 0.6rem 1rem;
            font-size: var(--font-size-sm);
            margin: 0.2rem;
            min-height: 40px;
        }
        #timer {
            min-width: 100px;
            padding: 0.4rem 0.8rem;
            font-size: var(--font-size-base);
        }
    }
    /* 18. Dark Mode Support */
    
    body.dark {
        background: var(--bg-gradient-end);
        color: var(--text-light);
    }
    
    body.dark .app-container {
        background: var(--card-bg-dark);
        color: var(--text-light);
    }
    
    body.dark .screen h1,
    body.dark .screen h2,
    body.dark .screen h3 {
        color: var(--text-lighter);
    }
    
    body.dark .screen p {
        color: #ccc;
    }
    
    body.dark #quiz-form label {
        background: #3a3a4a;
        border-color: #555;
        color: var(--text-light);
    }
    
    body.dark #quiz-form label:hover {
        background: #4a4a5a;
        border-color: var(--primary);
    }
    
    body.dark .input-field {
        background: #3a3a4a;
        border-color: #555;
        color: var(--text-light);
    }
    
    body.dark .input-field:focus {
        border-color: var(--primary);
    }
    
    body.dark .question-counter {
        background: rgba(33, 150, 243, 0.15);
        border-color: rgba(33, 150, 243, 0.3);
    }
    
    body.dark .quiz-header {
        background: rgba(50, 50, 60, 0.8);
    }
    
    body.dark .subject-btn {
        background: linear-gradient(135deg, var(--primary-dark), var(--secondary-dark));
    }
    
    body.dark .subject-btn:hover {
        background: linear-gradient(135deg, #018e73, #0a33ec);
    }
    
    ody.dark .subject-btn:hover {
        background: linear-gradient(135deg, #018e73, #0a33ec);
    }
    
    body.dark .subject-btn:hover {
        background: linear-gradient(135deg, #018e73, #0a33ec);
    }