/* ===== CSS Variables - Quantum Theme ===== */
:root {
    /* Colors */
    --color-bg-dark: #0A192F;
    --color-quantum-purple: #8B5CF6;
    --color-cyan: #22D3EE;
    --color-white: #F8FAFC;
    --color-gray-light: #E2E8F0;
    --color-gray-dark: #64748B;
    
    /* Gradients */
    --gradient-quantum: linear-gradient(135deg, var(--color-quantum-purple), var(--color-cyan));
    --gradient-dark: linear-gradient(180deg, var(--color-bg-dark), #0F1B3A);
    
    /* Shadows & Glows */
    --glow-purple: 0 0 20px rgba(139, 92, 246, 0.5);
    --glow-cyan: 0 0 20px rgba(34, 211, 238, 0.5);
    --shadow-glass: 0 8px 32px 0 rgba(31, 38, 135, 0.37);
    
    /* Transitions */
    --transition-smooth: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

/* ===== Reset & Base ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background: var(--color-bg-dark);
    color: var(--color-white);
    overflow-x: hidden;
    min-height: 100vh;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    /* Prevent text selection issues on mobile */
    -webkit-tap-highlight-color: rgba(139, 92, 246, 0.3);
}

/* ===== Particles Background ===== */
#particles-canvas {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 0;
    pointer-events: none;
}

/* ===== App Container ===== */
.app-container {
    position: relative;
    z-index: 1;
    min-height: 100vh;
}

/* ===== Screen Management ===== */
.screen {
    min-height: 100vh;
    padding: 2rem;
    display: flex;
    align-items: center;
    justify-content: center;
}

/* ===== Loading Screen ===== */
.loading-screen {
    flex-direction: column;
}

.quantum-spinner {
    width: 80px;
    height: 80px;
    border: 4px solid rgba(139, 92, 246, 0.2);
    border-top-color: var(--color-quantum-purple);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin-bottom: 2rem;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* ===== Home Screen ===== */
.home-content {
    max-width: 800px;
    width: 100%;
    text-align: center;
}

.main-title {
    font-family: 'Poppins', sans-serif;
    font-size: 3.5rem;
    font-weight: 700;
    margin-bottom: 1rem;
    line-height: 1.2;
}

.title-glow {
    display: inline-block;
    background: var(--gradient-quantum);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    text-shadow: var(--glow-purple);
    animation: glow-pulse 3s ease-in-out infinite;
}

@keyframes glow-pulse {
    0%, 100% { filter: brightness(1); }
    50% { filter: brightness(1.3); }
}

.subtitle {
    font-size: 1.25rem;
    color: var(--color-gray-light);
    margin-bottom: 3rem;
}

/* ===== Quiz Configuration ===== */
.quiz-config {
    background: rgba(15, 23, 42, 0.8);
    backdrop-filter: blur(10px);
    border-radius: 20px;
    padding: 2.5rem;
    border: 1px solid rgba(139, 92, 246, 0.2);
    box-shadow: var(--shadow-glass);
}

.config-item {
    margin-bottom: 2rem;
}

.config-item label {
    display: block;
    margin-bottom: 0.75rem;
    font-weight: 500;
    color: var(--color-gray-light);
}

/* Slider */
.slider-container {
    display: flex;
    align-items: center;
    gap: 1rem;
}

input[type="range"] {
    flex: 1;
    height: 8px;
    border-radius: 5px;
    background: rgba(139, 92, 246, 0.2);
    outline: none;
    -webkit-appearance: none;
}

input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: var(--gradient-quantum);
    cursor: pointer;
    box-shadow: var(--glow-purple);
}

input[type="range"]::-moz-range-thumb {
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: var(--gradient-quantum);
    cursor: pointer;
    border: none;
    box-shadow: var(--glow-purple);
}

.slider-value {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--color-cyan);
    min-width: 60px;
}

.estimated-time {
    display: block;
    margin-top: 0.5rem;
    font-size: 0.875rem;
    color: var(--color-gray-dark);
}

/* Mode Buttons */
.mode-buttons {
    display: flex;
    gap: 1rem;
    justify-content: center;
}

.mode-btn {
    flex: 1;
    padding: 1rem 1.5rem;
    background: rgba(139, 92, 246, 0.1);
    border: 2px solid rgba(139, 92, 246, 0.3);
    border-radius: 12px;
    color: var(--color-white);
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition-smooth);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
}

.mode-btn:hover {
    background: rgba(139, 92, 246, 0.2);
    border-color: var(--color-quantum-purple);
    transform: translateY(-2px);
}

.mode-btn.active {
    background: var(--gradient-quantum);
    border-color: var(--color-quantum-purple);
    box-shadow: var(--glow-purple);
}

.mode-btn .icon {
    font-size: 2rem;
}

/* Advanced Options */
.toggle-advanced {
    background: none;
    border: none;
    color: var(--color-cyan);
    cursor: pointer;
    font-size: 1rem;
    padding: 0.5rem;
    transition: var(--transition-smooth);
}

.toggle-advanced:hover {
    color: var(--color-quantum-purple);
}

.advanced-options {
    margin-top: 1rem;
    padding-top: 1rem;
    border-top: 1px solid rgba(139, 92, 246, 0.2);
}

.option-group {
    margin-bottom: 1rem;
}

select {
    width: 100%;
    padding: 0.75rem;
    background: rgba(139, 92, 246, 0.1);
    border: 1px solid rgba(139, 92, 246, 0.3);
    border-radius: 8px;
    color: var(--color-white);
    font-size: 1rem;
}

.checkbox-group {
    display: flex;
    gap: 1.5rem;
}

.checkbox-group label {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    cursor: pointer;
}

.switch-label {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    cursor: pointer;
}

.switch {
    position: relative;
    width: 50px;
    height: 26px;
    background: rgba(139, 92, 246, 0.2);
    border-radius: 13px;
    transition: var(--transition-smooth);
}

.switch::after {
    content: '';
    position: absolute;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: var(--color-white);
    top: 3px;
    left: 3px;
    transition: var(--transition-smooth);
}

input[type="checkbox"]:checked + .switch {
    background: var(--color-quantum-purple);
}

input[type="checkbox"]:checked + .switch::after {
    transform: translateX(24px);
}

/* Buttons */
.btn-primary, .btn-secondary, .btn-success, .btn-warning {
    padding: 1rem 2rem;
    border: none;
    border-radius: 12px;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition-smooth);
    position: relative;
    overflow: hidden;
}

.btn-primary {
    background: var(--gradient-quantum);
    color: var(--color-white);
    box-shadow: var(--glow-purple);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 10px 30px rgba(139, 92, 246, 0.6);
}

.start-btn {
    width: 100%;
    padding: 1.25rem;
    font-size: 1.25rem;
    margin-top: 2rem;
}

.btn-secondary {
    background: rgba(139, 92, 246, 0.2);
    color: var(--color-white);
    border: 1px solid rgba(139, 92, 246, 0.3);
}

.btn-secondary:hover {
    background: rgba(139, 92, 246, 0.3);
}

.btn-success {
    background: linear-gradient(135deg, #10B981, #059669);
}

.btn-warning {
    background: linear-gradient(135deg, #F59E0B, #D97706);
}

.icon-btn {
    background: rgba(139, 92, 246, 0.1);
    border: 1px solid rgba(139, 92, 246, 0.3);
    border-radius: 8px;
    color: var(--color-white);
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: var(--transition-smooth);
}

.icon-btn:hover {
    background: rgba(139, 92, 246, 0.2);
}

/* Personal Stats */
.personal-stats {
    margin-top: 2rem;
    padding-top: 2rem;
    border-top: 1px solid rgba(139, 92, 246, 0.2);
    color: var(--color-gray-light);
    font-size: 0.9rem;
}

.personal-stats span {
    color: var(--color-cyan);
    font-weight: 600;
}

/* ===== Quiz Screen ===== */
.quiz-header {
    background: rgba(15, 23, 42, 0.9);
    backdrop-filter: blur(10px);
    padding: 1.5rem 2rem;
    border-bottom: 1px solid rgba(139, 92, 246, 0.2);
    position: sticky;
    top: 0;
    z-index: 10;
}

.progress-container {
    margin-bottom: 1rem;
}

.progress-bar {
    height: 8px;
    background: rgba(139, 92, 246, 0.2);
    border-radius: 4px;
    overflow: hidden;
    margin-bottom: 0.75rem;
}

.progress-fill {
    height: 100%;
    background: var(--gradient-quantum);
    width: 0%;
    transition: width 0.3s ease;
    box-shadow: var(--glow-cyan);
}

.progress-info {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.9rem;
    color: var(--color-gray-light);
}

.timer {
    color: var(--color-cyan);
    font-weight: 600;
}

.quiz-controls {
    display: flex;
    gap: 0.5rem;
}

/* Quiz Content */
.quiz-content {
    max-width: 900px;
    margin: 2rem auto;
    padding: 0 2rem;
}

.question-container {
    background: rgba(15, 23, 42, 0.8);
    backdrop-filter: blur(10px);
    border-radius: 20px;
    padding: 2.5rem;
    border: 1px solid rgba(139, 92, 246, 0.2);
    box-shadow: var(--shadow-glass);
}

.question-text {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: 2rem;
    line-height: 1.6;
    color: var(--color-white);
}

/* QCM Options */
.options-container {
    display: grid;
    gap: 1rem;
}

.option {
    padding: 1.25rem;
    background: rgba(139, 92, 246, 0.1);
    border: 2px solid rgba(139, 92, 246, 0.3);
    border-radius: 12px;
    cursor: pointer;
    transition: var(--transition-smooth);
    font-size: 1.1rem;
    position: relative;
}

.option:hover {
    background: rgba(139, 92, 246, 0.2);
    border-color: var(--color-quantum-purple);
    transform: translateX(5px);
}

.option.selected {
    background: rgba(139, 92, 246, 0.3);
    border-color: var(--color-quantum-purple);
    box-shadow: var(--glow-purple);
}

.option.correct {
    background: rgba(16, 185, 129, 0.2);
    border-color: #10B981;
}

.option.incorrect {
    background: rgba(239, 68, 68, 0.2);
    border-color: #EF4444;
}

.option-number {
    display: inline-block;
    width: 30px;
    height: 30px;
    background: rgba(139, 92, 246, 0.3);
    border-radius: 50%;
    text-align: center;
    line-height: 30px;
    margin-right: 1rem;
    font-weight: 600;
}

/* Feedback */
.feedback-container {
    margin-top: 2rem;
    padding-top: 2rem;
    border-top: 1px solid rgba(139, 92, 246, 0.2);
}

.feedback-message {
    font-size: 1.2rem;
    font-weight: 600;
    margin-bottom: 1rem;
}

.feedback-message.correct {
    color: #10B981;
}

.feedback-message.incorrect {
    color: #EF4444;
}

.explanation {
    font-size: 1rem;
    line-height: 1.6;
    color: var(--color-gray-light);
    margin-top: 1rem;
}

.formula-display {
    background: rgba(139, 92, 246, 0.1);
    padding: 1rem;
    border-radius: 8px;
    margin: 1rem 0;
    font-family: 'Courier New', monospace;
    font-size: 1.1rem;
    border-left: 3px solid var(--color-quantum-purple);
}

/* Flashcard */
.flashcard-container {
    perspective: 1000px;
    width: 100%;
    display: flex;
    justify-content: center;
    align-items: flex-start;
    padding: 2rem 0;
}

.flashcard {
    width: 100%;
    max-width: 750px;
    position: relative;
}

.flashcard-inner {
    position: relative;
    width: 100%;
    transition: transform 0.6s;
    transform-style: preserve-3d;
}

.flashcard.flipped .flashcard-inner {
    transform: rotateY(180deg);
}

.flashcard-front {
    position: relative;
    width: 100%;
    backface-visibility: hidden;
    border-radius: 20px;
    padding: 2.5rem;
    display: flex;
    flex-direction: column;
    box-shadow: var(--shadow-glass);
    min-height: 400px;
    background: var(--gradient-quantum);
    border: 1px solid rgba(139, 92, 246, 0.3);
}

.flashcard-back {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    backface-visibility: hidden;
    border-radius: 20px;
    padding: 2.5rem;
    display: flex;
    flex-direction: column;
    box-shadow: var(--shadow-glass);
    background: rgba(15, 23, 42, 0.95);
    transform: rotateY(180deg);
    border: 1px solid rgba(139, 92, 246, 0.2);
    min-height: 400px;
}

.flashcard-content {
    flex: 1 1 auto;
    display: flex;
    flex-direction: column;
    min-height: 200px;
}

.flashcard-label {
    font-size: 0.875rem;
    text-transform: uppercase;
    letter-spacing: 2px;
    opacity: 0.9;
    margin-bottom: 1.5rem;
    font-weight: 600;
    flex-shrink: 0;
}

.flashcard-text {
    font-size: 1.25rem;
    line-height: 1.8;
    font-weight: 400;
    padding-right: 0.5rem;
    word-wrap: break-word;
    word-break: break-word;
    white-space: pre-wrap;
    overflow-wrap: break-word;
    margin-bottom: 1rem;
}

.flip-btn {
    margin-top: 2rem;
    padding: 1rem 2rem;
    width: 100%;
    flex-shrink: 0;
    font-size: 1rem;
}

.flashcard-actions {
    display: flex;
    gap: 1rem;
    margin-top: 2rem;
    padding-top: 1.5rem;
    border-top: 1px solid rgba(139, 92, 246, 0.2);
    flex-shrink: 0;
}

.flashcard-actions button {
    flex: 1;
    padding: 1rem;
    font-size: 1rem;
}

/* Ensure formula display is styled correctly */
.flashcard-back .formula-display {
    margin-top: 1rem;
    padding: 1rem;
    background: rgba(139, 92, 246, 0.1);
    border-radius: 8px;
    border-left: 3px solid var(--color-quantum-purple);
    font-family: 'Courier New', monospace;
    font-size: 1rem;
    overflow-x: auto;
}

/* Mobile adjustments for flashcards */
@media (max-width: 768px) {
    .flashcard-container {
        padding: 1rem 0;
    }
    
    .flashcard-front,
    .flashcard-back {
        min-height: 350px;
        padding: 1.5rem;
    }
    
    .flashcard-content {
        min-height: 150px;
    }
    
    .flashcard-text {
        font-size: 1.1rem;
        min-height: 120px;
    }
}

.next-btn {
    margin-top: 2rem;
    width: 100%;
}

.next-btn span {
    font-size: 0.875rem;
    opacity: 0.7;
}

/* ===== Results Screen ===== */
.results-content {
    max-width: 1000px;
    width: 100%;
}

.score-display-large {
    text-align: center;
    margin-bottom: 3rem;
}

.score-circle {
    width: 200px;
    height: 200px;
    margin: 0 auto 2rem;
    position: relative;
}

.score-circle svg {
    width: 100%;
    height: 100%;
    transform: rotate(-90deg);
}

.score-circle-bg {
    fill: none;
    stroke: rgba(139, 92, 246, 0.2);
    stroke-width: 8;
}

.score-circle-fill {
    fill: none;
    stroke: url(#gradient);
    stroke-width: 8;
    stroke-linecap: round;
    stroke-dasharray: 283;
    stroke-dashoffset: 283;
    transition: stroke-dashoffset 1s ease;
}

.score-text {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    text-align: center;
}

.score-percentage {
    display: block;
    font-size: 3rem;
    font-weight: 700;
    background: var(--gradient-quantum);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.score-grade {
    display: block;
    font-size: 1.25rem;
    color: var(--color-gray-light);
}

.score-message {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--color-cyan);
}

.statistics-section {
    margin-bottom: 3rem;
}

.statistics-section h2 {
    font-size: 2rem;
    margin-bottom: 1.5rem;
    text-align: center;
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1.5rem;
    margin-bottom: 2rem;
}

.stat-card {
    background: rgba(15, 23, 42, 0.8);
    backdrop-filter: blur(10px);
    padding: 1.5rem;
    border-radius: 12px;
    border: 1px solid rgba(139, 92, 246, 0.2);
    text-align: center;
}

.stat-value {
    font-size: 2.5rem;
    font-weight: 700;
    background: var(--gradient-quantum);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    margin-bottom: 0.5rem;
}

.stat-label {
    font-size: 0.9rem;
    color: var(--color-gray-light);
}

#stats-chart {
    max-height: 300px;
    margin: 0 auto;
}

.review-section {
    margin-bottom: 3rem;
}

.review-section h2 {
    font-size: 2rem;
    margin-bottom: 1.5rem;
}

.review-list {
    max-height: 500px;
    overflow-y: auto;
}

.review-item {
    background: rgba(15, 23, 42, 0.8);
    padding: 1.5rem;
    border-radius: 12px;
    margin-bottom: 1rem;
    border-left: 4px solid;
}

.review-item.correct {
    border-color: #10B981;
}

.review-item.incorrect {
    border-color: #EF4444;
}

.results-actions {
    display: flex;
    gap: 1rem;
    justify-content: center;
    flex-wrap: wrap;
}

/* ===== Modal ===== */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(10, 25, 47, 0.9);
    backdrop-filter: blur(5px);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
}

.modal-content {
    background: rgba(15, 23, 42, 0.95);
    padding: 2.5rem;
    border-radius: 20px;
    border: 1px solid rgba(139, 92, 246, 0.3);
    max-width: 500px;
    width: 90%;
    text-align: center;
}

.modal-content h2 {
    margin-bottom: 1rem;
}

.modal-actions {
    display: flex;
    gap: 1rem;
    margin-top: 2rem;
    justify-content: center;
}

/* ===== Responsive ===== */
/* Mobile devices (phones, small tablets) */
@media (max-width: 768px) {
    /* Base adjustments */
    body {
        font-size: 16px;
        -webkit-text-size-adjust: 100%;
    }
    
    .screen {
        padding: 1rem;
        min-height: 100vh;
        align-items: flex-start;
        padding-top: 1.5rem;
    }
    
    /* Home screen */
    .home-content {
        width: 100%;
        max-width: 100%;
    }
    
    .main-title {
        font-size: 2rem;
        line-height: 1.3;
        margin-bottom: 0.75rem;
    }
    
    .subtitle {
        font-size: 1rem;
        margin-bottom: 1.5rem;
    }
    
    .quiz-config {
        padding: 1.25rem;
        border-radius: 16px;
        margin: 0;
    }
    
    .config-item {
        margin-bottom: 1.5rem;
    }
    
    .config-item label {
        font-size: 0.95rem;
        margin-bottom: 0.5rem;
    }
    
    /* Slider adjustments */
    .slider-container {
        gap: 0.75rem;
    }
    
    .slider-value {
        font-size: 1.25rem;
        min-width: 50px;
    }
    
    input[type="range"] {
        height: 10px;
    }
    
    input[type="range"]::-webkit-slider-thumb {
        width: 24px;
        height: 24px;
    }
    
    input[type="range"]::-moz-range-thumb {
        width: 24px;
        height: 24px;
    }
    
    .estimated-time {
        font-size: 0.8rem;
    }
    
    /* Mode buttons */
    .mode-buttons {
        flex-direction: column;
        gap: 0.75rem;
    }
    
    .mode-btn {
        padding: 1rem;
        font-size: 0.95rem;
    }
    
    .mode-btn .icon {
        font-size: 1.75rem;
    }
    
    /* Advanced options */
    .advanced-options {
        padding-top: 0.75rem;
    }
    
    .option-group {
        margin-bottom: 0.75rem;
    }
    
    select {
        padding: 0.625rem;
        font-size: 0.95rem;
    }
    
    .checkbox-group {
        flex-direction: column;
        gap: 0.75rem;
    }
    
    /* Buttons */
    .start-btn {
        padding: 1rem;
        font-size: 1.1rem;
        margin-top: 1.5rem;
    }
    
    .btn-primary, .btn-secondary, .btn-success, .btn-warning {
        padding: 0.875rem 1.5rem;
        font-size: 1rem;
        min-height: 48px; /* Better touch target - WCAG recommendation */
        touch-action: manipulation; /* Prevent double-tap zoom */
        -webkit-tap-highlight-color: rgba(139, 92, 246, 0.3);
        cursor: pointer;
    }
    
    .btn-primary:active, .btn-secondary:active, 
    .btn-success:active, .btn-warning:active {
        transform: scale(0.98); /* Feedback tactile */
    }
    
    /* Personal stats */
    .personal-stats {
        margin-top: 1.5rem;
        padding-top: 1.5rem;
        font-size: 0.85rem;
    }
    
    /* Quiz screen */
    .quiz-header {
        padding: 1rem 1.25rem;
        position: sticky;
        top: 0;
        z-index: 10;
    }
    
    .progress-container {
        margin-bottom: 0.75rem;
    }
    
    .progress-bar {
        height: 6px;
        margin-bottom: 0.5rem;
    }
    
    .progress-info {
        font-size: 0.85rem;
        flex-wrap: wrap;
        gap: 0.5rem;
    }
    
    .quiz-controls {
        gap: 0.5rem;
    }
    
    .icon-btn {
        width: 44px;
        height: 44px;
        font-size: 1.1rem;
    }
    
    .quiz-content {
        padding: 0 1rem;
        margin: 1rem auto;
        max-width: 100%;
        /* Smooth scrolling on mobile */
        -webkit-overflow-scrolling: touch;
    }
    
    .question-container {
        padding: 1.5rem;
        border-radius: 16px;
    }
    
    .question-text {
        font-size: 1.2rem;
        margin-bottom: 1.5rem;
        line-height: 1.5;
    }
    
    /* QCM Options */
    .options-container {
        grid-template-columns: 1fr;
        gap: 0.75rem;
    }
    
    .option {
        padding: 1rem;
        font-size: 1rem;
        border-radius: 10px;
        min-height: 48px; /* Better touch target - WCAG recommendation */
        display: flex;
        align-items: center;
        touch-action: manipulation; /* Prevent double-tap zoom */
        -webkit-tap-highlight-color: rgba(139, 92, 246, 0.3);
        cursor: pointer;
    }
    
    .option:active {
        transform: scale(0.98); /* Feedback tactile */
        background: rgba(139, 92, 246, 0.25);
    }
    
    .option:hover {
        transform: none; /* Disable hover transform on mobile */
    }
    
    .option-number {
        width: 28px;
        height: 28px;
        line-height: 28px;
        font-size: 0.9rem;
        margin-right: 0.75rem;
        flex-shrink: 0;
    }
    
    .feedback-container {
        margin-top: 1.5rem;
        padding-top: 1.5rem;
    }
    
    .feedback-message {
        font-size: 1.1rem;
        margin-bottom: 0.75rem;
    }
    
    .explanation {
        font-size: 0.95rem;
        line-height: 1.5;
    }
    
    .formula-display {
        padding: 0.875rem;
        font-size: 0.95rem;
        overflow-x: auto;
        -webkit-overflow-scrolling: touch;
    }
    
    .next-btn {
        margin-top: 1.5rem;
        width: 100%;
        padding: 1rem;
        font-size: 1.05rem;
        min-height: 50px;
    }
    
    /* Flashcard */
    .flashcard-container {
        padding: 1rem 0;
        width: 100%;
    }
    
    .flashcard {
        max-width: 100%;
    }
    
    .flashcard-front,
    .flashcard-back {
        padding: 1.5rem;
        min-height: 350px;
        border-radius: 16px;
    }
    
    .flashcard-content {
        min-height: 150px;
    }
    
    .flashcard-label {
        font-size: 0.75rem;
        margin-bottom: 1rem;
    }
    
    .flashcard-text {
        font-size: 1.1rem;
        line-height: 1.6;
        min-height: 100px;
    }
    
    .flip-btn {
        margin-top: 1.5rem;
        padding: 0.875rem;
        font-size: 0.95rem;
        min-height: 48px;
    }
    
    .flashcard-actions {
        gap: 0.75rem;
        margin-top: 1.5rem;
        padding-top: 1rem;
    }
    
    .flashcard-actions button {
        padding: 0.875rem;
        font-size: 0.95rem;
        min-height: 48px;
    }
    
    /* Results screen */
    .results-content {
        width: 100%;
        max-width: 100%;
    }
    
    .score-display-large {
        margin-bottom: 2rem;
    }
    
    .score-circle {
        width: 150px;
        height: 150px;
        margin-bottom: 1.5rem;
    }
    
    .score-percentage {
        font-size: 2.25rem;
    }
    
    .score-grade {
        font-size: 1rem;
    }
    
    .score-message {
        font-size: 1.2rem;
        padding: 0 1rem;
    }
    
    .statistics-section {
        margin-bottom: 2rem;
    }
    
    .statistics-section h2 {
        font-size: 1.5rem;
        margin-bottom: 1rem;
    }
    
    .stats-grid {
        grid-template-columns: 1fr;
        gap: 1rem;
        margin-bottom: 1.5rem;
    }
    
    .stat-card {
        padding: 1.25rem;
    }
    
    .stat-value {
        font-size: 2rem;
    }
    
    .stat-label {
        font-size: 0.85rem;
    }
    
    #stats-chart {
        max-height: 250px;
    }
    
    .review-section {
        margin-bottom: 2rem;
    }
    
    .review-section h2 {
        font-size: 1.5rem;
        margin-bottom: 1rem;
    }
    
    .review-list {
        max-height: 400px;
        -webkit-overflow-scrolling: touch; /* Smooth scrolling on iOS */
        overflow-y: auto;
    }
    
    .review-item {
        padding: 1.25rem;
        font-size: 0.9rem;
    }
    
    .results-actions {
        flex-direction: column;
        gap: 0.75rem;
    }
    
    .results-actions button {
        width: 100%;
        min-height: 50px;
    }
    
    /* Modal */
    .modal-content {
        padding: 1.5rem;
        margin: 1rem;
        width: calc(100% - 2rem);
    }
    
    .modal-content h2 {
        font-size: 1.5rem;
    }
    
    .modal-actions {
        flex-direction: column;
        gap: 0.75rem;
    }
    
    .modal-actions button {
        width: 100%;
        min-height: 50px;
    }
}

/* Very small screens */
@media (max-width: 480px) {
    .screen {
        padding: 0.75rem;
    }
    
    .main-title {
        font-size: 1.75rem;
    }
    
    .quiz-config {
        padding: 1rem;
    }
    
    .question-container {
        padding: 1.25rem;
    }
    
    .question-text {
        font-size: 1.1rem;
    }
    
    .option {
        padding: 0.875rem;
        font-size: 0.95rem;
    }
    
    .flashcard-front,
    .flashcard-back {
        padding: 1.25rem;
        min-height: 300px;
    }
    
    .flashcard-text {
        font-size: 1rem;
    }
    
    .score-circle {
        width: 120px;
        height: 120px;
    }
    
    .score-percentage {
        font-size: 1.75rem;
    }
}

/* Landscape orientation on mobile */
@media (max-width: 768px) and (orientation: landscape) {
    .screen {
        padding: 1rem;
    }
    
    .main-title {
        font-size: 1.75rem;
        margin-bottom: 0.5rem;
    }
    
    .subtitle {
        font-size: 0.9rem;
        margin-bottom: 1rem;
    }
    
    .quiz-config {
        padding: 1rem;
    }
    
    .quiz-content {
        margin: 0.5rem auto;
    }
    
    .question-container {
        padding: 1.25rem;
    }
    
    .flashcard-front,
    .flashcard-back {
        min-height: 280px;
        padding: 1.25rem;
    }
}

@media (prefers-reduced-motion: reduce) {
    * {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}