/* ===== CSS Variables ===== */
:root {
    /* Colors - Dark Theme */
    --bg-primary: #0a0a0f;
    --bg-secondary: #12121a;
    --bg-card: rgba(30, 30, 45, 0.8);
    --bg-glass: rgba(255, 255, 255, 0.05);

    /* Gradient Colors */
    --gradient-primary: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --gradient-secondary: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    --gradient-accent: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
    --gradient-card: linear-gradient(145deg, #1a1a2e 0%, #16213e 100%);

    /* Text Colors */
    --text-primary: #ffffff;
    --text-secondary: rgba(255, 255, 255, 0.7);
    --text-muted: rgba(255, 255, 255, 0.5);

    /* Accent Colors */
    --accent-purple: #667eea;
    --accent-pink: #f093fb;
    --accent-blue: #4facfe;
    --accent-yellow: #ffd700;

    /* Shadows */
    --shadow-glow: 0 0 40px rgba(102, 126, 234, 0.3);
    --shadow-card: 0 8px 32px rgba(0, 0, 0, 0.4);
    --shadow-button: 0 4px 15px rgba(102, 126, 234, 0.4);

    /* Borders */
    --border-glass: 1px solid rgba(255, 255, 255, 0.1);

    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;

    /* Border Radius */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 20px;
    --radius-xl: 24px;

    /* Transitions */
    --transition-fast: 0.2s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;
}

/* ===== Light Theme ===== */
[data-theme="light"] {
    --bg-primary: #f5f7fa;
    --bg-secondary: #ffffff;
    --bg-card: rgba(255, 255, 255, 0.9);
    --bg-glass: rgba(0, 0, 0, 0.05);

    --gradient-card: linear-gradient(145deg, #ffffff 0%, #f0f4f8 100%);

    --text-primary: #1a1a2e;
    --text-secondary: rgba(26, 26, 46, 0.7);
    --text-muted: rgba(26, 26, 46, 0.5);

    --shadow-glow: 0 0 40px rgba(102, 126, 234, 0.15);
    --shadow-card: 0 8px 32px rgba(0, 0, 0, 0.1);
    --shadow-button: 0 4px 15px rgba(102, 126, 234, 0.25);

    --border-glass: 1px solid rgba(0, 0, 0, 0.1);
}

[data-theme="light"] body::before {
    background:
        radial-gradient(circle at 20% 80%, rgba(102, 126, 234, 0.1) 0%, transparent 50%),
        radial-gradient(circle at 80% 20%, rgba(240, 147, 251, 0.1) 0%, transparent 50%),
        radial-gradient(circle at 40% 40%, rgba(79, 172, 254, 0.08) 0%, transparent 40%);
}

[data-theme="light"] .card-front {
    border-color: rgba(102, 126, 234, 0.2);
}

[data-theme="light"] .card-back {
    background: linear-gradient(145deg, #ffffff 0%, #f8f9fc 100%);
    border-color: rgba(240, 147, 251, 0.2);
}

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

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: 'Noto Sans KR', -apple-system, BlinkMacSystemFont, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    min-height: 100vh;
    line-height: 1.6;
    overflow-x: hidden;
    transition: background-color var(--transition-normal), color var(--transition-normal);
}

/* Background Pattern */
body::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background:
        radial-gradient(circle at 20% 80%, rgba(102, 126, 234, 0.15) 0%, transparent 50%),
        radial-gradient(circle at 80% 20%, rgba(240, 147, 251, 0.15) 0%, transparent 50%),
        radial-gradient(circle at 40% 40%, rgba(79, 172, 254, 0.1) 0%, transparent 40%);
    pointer-events: none;
    z-index: -1;
}

/* Screen Reader Only */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    border: 0;
}

/* ===== Theme Toggle ===== */
.header-top {
    display: flex;
    justify-content: flex-end;
    margin-bottom: var(--spacing-sm);
}

.theme-toggle {
    width: 44px;
    height: 44px;
    border-radius: 50%;
    background: var(--bg-glass);
    border: var(--border-glass);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-fast);
}

.theme-toggle:hover {
    background: rgba(255, 255, 255, 0.1);
    transform: scale(1.1);
}

.theme-toggle svg {
    width: 22px;
    height: 22px;
    color: var(--text-primary);
    transition: all var(--transition-normal);
}

.theme-toggle .icon-sun {
    display: none;
}

.theme-toggle .icon-moon {
    display: block;
}

[data-theme="light"] .theme-toggle .icon-sun {
    display: block;
}

[data-theme="light"] .theme-toggle .icon-moon {
    display: none;
}

/* ===== Cookie Banner ===== */
.cookie-banner {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    background: rgba(18, 18, 26, 0.95);
    backdrop-filter: blur(10px);
    border-top: var(--border-glass);
    padding: var(--spacing-md);
    z-index: 1000;
    transform: translateY(0);
    transition: transform var(--transition-normal);
}

.cookie-banner.hidden {
    transform: translateY(100%);
}

.cookie-content {
    max-width: 600px;
    margin: 0 auto;
    text-align: center;
}

.cookie-content p {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-sm);
    font-size: 0.9rem;
}

.cookie-buttons {
    display: flex;
    gap: var(--spacing-sm);
    justify-content: center;
}

/* ===== Daily Question ===== */
.daily-question {
    margin-top: var(--spacing-md);
    padding: var(--spacing-sm) var(--spacing-md);
    background: var(--gradient-secondary);
    border-radius: var(--radius-lg);
    text-align: center;
    animation: dailyPulse 3s ease-in-out infinite;
}

.daily-question.hidden {
    display: none;
}

.daily-badge {
    display: inline-block;
    font-size: 0.75rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 1px;
    margin-bottom: 0.25rem;
}

.daily-text {
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--text-primary);
}

@keyframes dailyPulse {

    0%,
    100% {
        box-shadow: 0 0 0 0 rgba(240, 147, 251, 0.4);
    }

    50% {
        box-shadow: 0 0 20px 5px rgba(240, 147, 251, 0.2);
    }
}

/* ===== Ad Containers ===== */
.ad-container {
    background: var(--bg-secondary);
    border: var(--border-glass);
    text-align: center;
    padding: var(--spacing-sm);
    position: relative;
}

.ad-label {
    position: absolute;
    top: 4px;
    left: 8px;
    font-size: 0.65rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 1px;
}

.ad-placeholder {
    color: var(--text-muted);
    font-size: 0.8rem;
    padding: var(--spacing-md);
}

.ad-top {
    border-bottom: var(--border-glass);
}

.ad-bottom {
    border-top: var(--border-glass);
}

/* ===== Container ===== */
.container {
    max-width: 480px;
    margin: 0 auto;
    padding: var(--spacing-md);
    min-height: calc(100vh - 200px);
    display: flex;
    flex-direction: column;
}

/* ===== Header ===== */
.header {
    text-align: center;
    padding: var(--spacing-sm) 0 var(--spacing-lg);
}

.title {
    font-size: 1.8rem;
    font-weight: 900;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--spacing-xs);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.3rem;
}

.title .emoji {
    font-size: 2.5rem;
    -webkit-text-fill-color: initial;
}

.title .subtitle {
    font-size: 1.4rem;
    background: var(--gradient-secondary);
    -webkit-background-clip: text;
    background-clip: text;
}

.description {
    color: var(--text-secondary);
    font-size: 0.95rem;
}

/* ===== Categories ===== */
.categories {
    margin-bottom: var(--spacing-lg);
}

.category-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--spacing-xs);
}

.category-btn {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.25rem;
    padding: var(--spacing-xs) 0.25rem;
    background: var(--bg-glass);
    border: var(--border-glass);
    border-radius: var(--radius-md);
    color: var(--text-secondary);
    cursor: pointer;
    transition: all var(--transition-fast);
    font-family: inherit;
    position: relative;
}

.category-btn:hover {
    background: rgba(255, 255, 255, 0.1);
    transform: translateY(-2px);
}

.category-btn.active {
    background: var(--gradient-primary);
    color: var(--text-primary);
    border-color: transparent;
    box-shadow: var(--shadow-button);
}

.category-emoji {
    font-size: 1.3rem;
}

.category-name {
    font-size: 0.7rem;
    font-weight: 500;
    white-space: nowrap;
}

.favorites-count {
    position: absolute;
    top: -4px;
    right: -4px;
    min-width: 18px;
    height: 18px;
    background: var(--gradient-secondary);
    border-radius: 50%;
    font-size: 0.65rem;
    font-weight: 700;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
}

/* ===== Card Area ===== */
.card-area {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-md);
}

.card-deck {
    perspective: 1000px;
    width: 100%;
    max-width: 320px;
}

.card {
    width: 100%;
    aspect-ratio: 3/4;
    cursor: pointer;
    position: relative;
}

.card-inner {
    width: 100%;
    height: 100%;
    position: relative;
    transform-style: preserve-3d;
    transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
}

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

.card-front,
.card-back {
    position: absolute;
    width: 100%;
    height: 100%;
    -webkit-backface-visibility: hidden;
    backface-visibility: hidden;
    border-radius: var(--radius-xl);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-lg);
}

/* Card Front */
.card-front {
    background: var(--gradient-card);
    border: 2px solid rgba(102, 126, 234, 0.3);
    box-shadow: var(--shadow-card), var(--shadow-glow);
    overflow: hidden;
}

.card-pattern {
    position: absolute;
    width: 100%;
    height: 100%;
    background:
        repeating-linear-gradient(45deg,
            transparent,
            transparent 20px,
            rgba(102, 126, 234, 0.05) 20px,
            rgba(102, 126, 234, 0.05) 40px);
}

.card-tap-hint {
    color: var(--text-secondary);
    font-size: 1rem;
    font-weight: 500;
    z-index: 1;
    animation: pulse 2s infinite;
}

@keyframes pulse {

    0%,
    100% {
        opacity: 0.6;
        transform: scale(1);
    }

    50% {
        opacity: 1;
        transform: scale(1.05);
    }
}

/* Card Back */
.card-back {
    background: linear-gradient(145deg, #1e1e2e 0%, #2a2a4a 100%);
    border: 2px solid rgba(240, 147, 251, 0.3);
    box-shadow: var(--shadow-card);
    transform: rotateY(180deg);
    text-align: center;
    position: relative;
}

.favorite-btn {
    position: absolute;
    top: var(--spacing-sm);
    right: var(--spacing-sm);
    width: 36px;
    height: 36px;
    border: none;
    background: var(--bg-glass);
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-fast);
    z-index: 10;
}

.favorite-btn svg {
    width: 20px;
    height: 20px;
    color: var(--text-secondary);
    transition: all var(--transition-fast);
}

.favorite-btn:hover {
    transform: scale(1.1);
}

.favorite-btn.active svg {
    fill: var(--accent-yellow);
    stroke: var(--accent-yellow);
    animation: starPop 0.3s ease;
}

@keyframes starPop {
    0% {
        transform: scale(1);
    }

    50% {
        transform: scale(1.3);
    }

    100% {
        transform: scale(1);
    }
}

.question-text {
    font-size: 1.25rem;
    font-weight: 500;
    line-height: 1.6;
    color: var(--text-primary);
    margin-bottom: var(--spacing-md);
}

.question-category {
    position: absolute;
    bottom: var(--spacing-md);
    font-size: 0.8rem;
    color: var(--text-muted);
    background: var(--bg-glass);
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
}

/* Card Stats */
.card-stats {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-xs);
}

.card-counter {
    color: var(--text-muted);
    font-size: 0.85rem;
}

.milestone-badge {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    background: var(--gradient-secondary);
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    font-size: 0.75rem;
    font-weight: 600;
    animation: milestoneAppear 0.5s ease;
}

.milestone-badge.hidden {
    display: none;
}

@keyframes milestoneAppear {
    from {
        opacity: 0;
        transform: scale(0.8) translateY(-10px);
    }

    to {
        opacity: 1;
        transform: scale(1) translateY(0);
    }
}

/* ===== Buttons ===== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-xs);
    padding: 0.875rem 1.5rem;
    border: none;
    border-radius: var(--radius-lg);
    font-family: inherit;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.btn-icon {
    width: 20px;
    height: 20px;
}

.btn-primary {
    background: var(--gradient-primary);
    color: var(--text-primary);
    box-shadow: var(--shadow-button);
}

.btn-primary:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(102, 126, 234, 0.5);
}

.btn-secondary {
    background: var(--bg-glass);
    color: var(--text-secondary);
    border: var(--border-glass);
}

.btn-secondary:hover:not(:disabled) {
    background: rgba(255, 255, 255, 0.1);
}

.btn-glow {
    background: var(--gradient-primary);
    color: var(--text-primary);
    box-shadow: var(--shadow-button);
    position: relative;
    overflow: hidden;
}

.btn-glow::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: left 0.5s;
}

.btn-glow:hover:not(:disabled)::before {
    left: 100%;
}

.btn-glow:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: 0 6px 25px rgba(102, 126, 234, 0.6);
}

.action-buttons {
    display: flex;
    gap: var(--spacing-sm);
    flex-wrap: wrap;
    justify-content: center;
}

/* ===== Share Section ===== */
.share-section {
    margin-top: var(--spacing-md);
    text-align: center;
}

.share-label {
    font-size: 0.85rem;
    color: var(--text-muted);
    margin-bottom: var(--spacing-sm);
}

.share-buttons {
    display: flex;
    gap: var(--spacing-sm);
    justify-content: center;
}

.share-btn {
    width: 48px;
    height: 48px;
    border-radius: 50%;
    border: none;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-fast);
}

.share-btn svg {
    width: 24px;
    height: 24px;
}

.share-btn:hover {
    transform: translateY(-3px) scale(1.1);
}

.share-kakao {
    background: #FEE500;
    color: #3C1E1E;
}

.share-twitter {
    background: #1DA1F2;
    color: white;
}

.share-copy {
    background: var(--gradient-primary);
    color: white;
}

.share-image {
    background: var(--gradient-secondary);
    color: white;
}

/* ===== Modal ===== */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    z-index: 1001;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-md);
}

.modal.hidden {
    display: none;
}

.modal-backdrop {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.8);
    backdrop-filter: blur(5px);
}

.modal-content {
    position: relative;
    background: var(--bg-secondary);
    border-radius: var(--radius-xl);
    padding: var(--spacing-lg);
    max-width: 400px;
    width: 100%;
    border: var(--border-glass);
    animation: modalAppear 0.3s ease;
}

@keyframes modalAppear {
    from {
        opacity: 0;
        transform: scale(0.9);
    }

    to {
        opacity: 1;
        transform: scale(1);
    }
}

.modal-close {
    position: absolute;
    top: var(--spacing-sm);
    right: var(--spacing-sm);
    width: 36px;
    height: 36px;
    border: none;
    background: var(--bg-glass);
    border-radius: 50%;
    font-size: 1.5rem;
    color: var(--text-secondary);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-fast);
}

.modal-close:hover {
    background: rgba(255, 255, 255, 0.1);
}

.modal-title {
    text-align: center;
    font-size: 1.25rem;
    margin-bottom: var(--spacing-md);
    color: var(--text-primary);
}

.share-card-preview {
    background: var(--gradient-card);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    text-align: center;
    position: relative;
    margin-bottom: var(--spacing-md);
    min-height: 200px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}

.preview-question {
    font-size: 1.1rem;
    font-weight: 500;
    color: var(--text-primary);
    margin-bottom: var(--spacing-sm);
}

.preview-category {
    font-size: 0.8rem;
    color: var(--text-muted);
    background: var(--bg-glass);
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
}

.preview-watermark {
    position: absolute;
    bottom: var(--spacing-sm);
    right: var(--spacing-sm);
    font-size: 0.6rem;
    color: var(--text-muted);
    opacity: 0.5;
}

.modal-actions {
    display: flex;
    gap: var(--spacing-sm);
    justify-content: center;
}

/* ===== Toast ===== */
.toast {
    position: fixed;
    bottom: 100px;
    left: 50%;
    transform: translateX(-50%);
    background: var(--bg-secondary);
    color: var(--text-primary);
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--radius-lg);
    border: var(--border-glass);
    box-shadow: var(--shadow-card);
    z-index: 1002;
    animation: toastAppear 0.3s ease;
}

.toast.hidden {
    display: none;
}

@keyframes toastAppear {
    from {
        opacity: 0;
        transform: translateX(-50%) translateY(20px);
    }

    to {
        opacity: 1;
        transform: translateX(-50%) translateY(0);
    }
}

/* ===== Footer ===== */
.footer {
    background: var(--bg-secondary);
    border-top: var(--border-glass);
    padding: var(--spacing-lg) var(--spacing-md);
    margin-top: auto;
}

.footer-content {
    max-width: 480px;
    margin: 0 auto;
    text-align: center;
}

.footer-links {
    margin-bottom: var(--spacing-sm);
}

.footer-links a {
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.85rem;
    transition: color var(--transition-fast);
}

.footer-links a:hover {
    color: var(--accent-purple);
}

.footer-links .divider {
    color: var(--text-muted);
    margin: 0 var(--spacing-sm);
}

.copyright {
    color: var(--text-muted);
    font-size: 0.75rem;
    margin-bottom: 0.25rem;
}

.contact {
    color: var(--text-muted);
    font-size: 0.75rem;
}

/* ===== Responsive ===== */
@media (max-width: 400px) {
    .category-grid {
        grid-template-columns: repeat(3, 1fr);
    }

    .title {
        font-size: 1.5rem;
    }

    .question-text {
        font-size: 1.1rem;
    }

    .action-buttons {
        flex-direction: column;
        width: 100%;
    }

    .action-buttons .btn {
        width: 100%;
    }
}

@media (min-width: 768px) {
    .container {
        padding: var(--spacing-xl);
    }

    .title {
        font-size: 2.2rem;
    }

    .category-grid {
        grid-template-columns: repeat(6, 1fr);
    }

    .card-deck {
        max-width: 360px;
    }
}

/* ===== Animations ===== */
@keyframes shake {

    0%,
    100% {
        transform: translateX(0);
    }

    25% {
        transform: translateX(-5px) rotate(-1deg);
    }

    75% {
        transform: translateX(5px) rotate(1deg);
    }
}

.card-deck.shake {
    animation: shake 0.5s ease-in-out;
}

/* Hidden utility */
.hidden {
    display: none !important;
}

/* Confetti animation for celebrations */
@keyframes confettiFall {
    0% {
        transform: translateY(-100%) rotate(0deg);
        opacity: 1;
    }

    100% {
        transform: translateY(100vh) rotate(720deg);
        opacity: 0;
    }
}

.confetti {
    position: fixed;
    top: 0;
    width: 10px;
    height: 10px;
    animation: confettiFall 3s ease-out forwards;
    z-index: 1000;
    pointer-events: none;
}