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

:root {
    --primary: #c0392b;
    --primary-light: #e74c3c;
    --primary-dark: #96281b;
    --accent: #d4a017;
    --accent-light: #f0c040;
    --bg: #faf8f5;
    --bg-card: #ffffff;
    --bg-dark: #1a1a2e;
    --text: #2c2c2c;
    --text-light: #666;
    --text-muted: #999;
    --border: #e8e4df;
    --shadow: 0 2px 12px rgba(0, 0, 0, 0.08);
    --shadow-hover: 0 6px 24px rgba(0, 0, 0, 0.12);
    --radius: 12px;
    --radius-sm: 8px;
    --transition: 0.25s ease;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.6;
    min-height: 100vh;
}

/* === Header === */
header {
    position: sticky;
    top: 0;
    z-index: 100;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border);
}

.header-inner {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 64px;
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
    cursor: pointer;
    text-decoration: none;
}

.logo-icon {
    font-size: 28px;
    background: var(--primary);
    color: white;
    width: 42px;
    height: 42px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: var(--radius-sm);
    font-weight: 700;
}

.logo-text {
    font-size: 18px;
    font-weight: 700;
    color: var(--text);
}

nav {
    display: flex;
    gap: 4px;
}

.nav-btn {
    background: none;
    border: none;
    padding: 8px 16px;
    font-size: 14px;
    font-weight: 500;
    color: var(--text-light);
    cursor: pointer;
    border-radius: var(--radius-sm);
    transition: var(--transition);
    font-family: inherit;
}

.nav-btn:hover {
    background: rgba(192, 57, 43, 0.08);
    color: var(--primary);
}

.nav-btn.active {
    background: rgba(192, 57, 43, 0.1);
    color: var(--primary);
    font-weight: 600;
}

.menu-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
}

.menu-toggle span {
    width: 24px;
    height: 2px;
    background: var(--text);
    border-radius: 2px;
    transition: var(--transition);
}

/* === Pages === */
.page {
    display: none;
    max-width: 1200px;
    margin: 0 auto;
    padding: 40px 24px 80px;
    animation: fadeIn 0.3s ease;
}

.page.active {
    display: block;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.page-header {
    margin-bottom: 40px;
}

.page-header h1 {
    font-size: 32px;
    font-weight: 700;
    margin-bottom: 8px;
}

.page-header p {
    color: var(--text-light);
    font-size: 16px;
}

/* === Hero === */
.hero {
    text-align: center;
    padding: 60px 20px 50px;
}

.hero h1 {
    font-size: 42px;
    line-height: 1.2;
    font-weight: 400;
    margin-bottom: 16px;
}

.hero h1 strong {
    color: var(--primary);
    font-weight: 700;
}

.hero-sub {
    font-size: 17px;
    color: var(--text-light);
    max-width: 600px;
    margin: 0 auto 32px;
    line-height: 1.7;
}

.hero-actions {
    display: flex;
    gap: 12px;
    justify-content: center;
    flex-wrap: wrap;
}

/* === Buttons === */
.btn {
    padding: 12px 28px;
    border-radius: var(--radius-sm);
    font-size: 15px;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    border: 2px solid transparent;
    font-family: inherit;
}

.btn-primary {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
}

.btn-primary:hover {
    background: var(--primary-dark);
    border-color: var(--primary-dark);
    transform: translateY(-1px);
    box-shadow: var(--shadow);
}

.btn-outline {
    background: transparent;
    color: var(--primary);
    border-color: var(--primary);
}

.btn-outline:hover {
    background: var(--primary);
    color: white;
    transform: translateY(-1px);
}

.btn-back {
    background: none;
    border: none;
    color: var(--primary);
    padding: 8px 0;
    font-size: 15px;
    margin-bottom: 20px;
    cursor: pointer;
    font-family: inherit;
    font-weight: 500;
}

.btn-back:hover {
    color: var(--primary-dark);
}

/* === Features === */
.features {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 24px;
    margin-bottom: 60px;
}

.feature-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 32px 24px;
    text-align: center;
    cursor: pointer;
    transition: var(--transition);
}

.feature-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-hover);
    border-color: var(--primary);
}

.feature-icon {
    font-size: 40px;
    margin-bottom: 16px;
}

.feature-card h3 {
    font-size: 18px;
    margin-bottom: 8px;
}

.feature-card p {
    color: var(--text-light);
    font-size: 14px;
    line-height: 1.6;
}

/* === Daily Word === */
.daily-word {
    text-align: center;
}

.daily-word h2 {
    font-size: 24px;
    margin-bottom: 20px;
}

.word-spotlight {
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    color: white;
    border-radius: var(--radius);
    padding: 40px;
    max-width: 500px;
    margin: 0 auto;
    box-shadow: var(--shadow);
}

.word-spotlight .hanzi {
    font-size: 56px;
    font-weight: 700;
    margin-bottom: 8px;
}

.word-spotlight .peng-im {
    font-size: 20px;
    opacity: 0.9;
    margin-bottom: 4px;
}

.word-spotlight .meaning {
    font-size: 18px;
    opacity: 0.85;
    margin-bottom: 12px;
}

.word-spotlight .han-viet {
    font-size: 14px;
    background: rgba(255, 255, 255, 0.15);
    display: inline-block;
    padding: 4px 14px;
    border-radius: 20px;
}

/* === Category Grid === */
.category-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
    gap: 20px;
}

.category-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 28px 24px;
    cursor: pointer;
    transition: var(--transition);
    position: relative;
    overflow: hidden;
}

.category-card:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-hover);
    border-color: var(--primary);
}

.category-card .cat-icon {
    font-size: 36px;
    margin-bottom: 12px;
}

.category-card h3 {
    font-size: 17px;
    margin-bottom: 4px;
}

.category-card .cat-count {
    font-size: 13px;
    color: var(--text-muted);
}

/* === Vocab Cards === */
.vocab-cards {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 16px;
}

.vocab-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 24px;
    transition: var(--transition);
    cursor: pointer;
    position: relative;
}

.vocab-card:hover {
    box-shadow: var(--shadow);
    border-color: var(--accent);
}

.vocab-card .vc-hanzi {
    font-size: 36px;
    font-weight: 700;
    color: var(--primary);
    margin-bottom: 4px;
}

.vocab-card .vc-pengim {
    font-size: 16px;
    color: var(--accent);
    font-weight: 600;
    margin-bottom: 8px;
}

.vocab-card .vc-meaning {
    font-size: 15px;
    margin-bottom: 4px;
}

.vocab-card .vc-hanviet {
    font-size: 13px;
    color: var(--text-muted);
    font-style: italic;
}

.vocab-card .vc-example {
    margin-top: 12px;
    padding-top: 12px;
    border-top: 1px solid var(--border);
    font-size: 14px;
    color: var(--text-light);
}

.vocab-card.flipped .vc-back {
    display: block;
}

.vocab-card .vc-back {
    display: none;
}

.vocab-card .flip-hint {
    display: none;
}

/* === Quiz === */
.quiz-setup {
    max-width: 500px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.quiz-options label {
    display: block;
    font-weight: 600;
    margin-bottom: 6px;
    font-size: 14px;
}

.quiz-options select {
    width: 100%;
    padding: 10px 14px;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    font-size: 15px;
    font-family: inherit;
    background: var(--bg-card);
    cursor: pointer;
}

.quiz-area {
    max-width: 600px;
    margin: 0 auto;
}

.quiz-progress {
    margin-bottom: 30px;
    text-align: center;
}

#quiz-progress-text {
    font-size: 14px;
    color: var(--text-light);
    display: block;
    margin-bottom: 8px;
}

.progress-bar {
    height: 6px;
    background: var(--border);
    border-radius: 3px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: var(--primary);
    border-radius: 3px;
    transition: width 0.4s ease;
    width: 0%;
}

.quiz-question {
    text-align: center;
    margin-bottom: 28px;
}

.quiz-question .qq-label {
    font-size: 14px;
    color: var(--text-muted);
    margin-bottom: 10px;
}

.quiz-question .qq-prompt {
    font-size: 40px;
    font-weight: 700;
    color: var(--primary);
}

.quiz-question .qq-prompt-sub {
    font-size: 18px;
    color: var(--text-light);
    margin-top: 6px;
}

.quiz-answers {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 12px;
    margin-bottom: 24px;
}

.quiz-answer-btn {
    padding: 16px;
    background: var(--bg-card);
    border: 2px solid var(--border);
    border-radius: var(--radius-sm);
    font-size: 16px;
    cursor: pointer;
    transition: var(--transition);
    font-family: inherit;
    text-align: center;
}

.quiz-answer-btn:hover:not(.disabled) {
    border-color: var(--primary);
    background: rgba(192, 57, 43, 0.04);
}

.quiz-answer-btn.correct {
    border-color: #27ae60;
    background: rgba(39, 174, 96, 0.1);
    color: #27ae60;
    font-weight: 600;
}

.quiz-answer-btn.wrong {
    border-color: #e74c3c;
    background: rgba(231, 76, 60, 0.1);
    color: #e74c3c;
}

.quiz-answer-btn.disabled {
    cursor: default;
    opacity: 0.7;
}

.quiz-result {
    text-align: center;
    max-width: 400px;
    margin: 0 auto;
}

.quiz-score {
    font-size: 64px;
    font-weight: 700;
    color: var(--primary);
    margin: 20px 0;
}

.quiz-score .score-label {
    font-size: 16px;
    color: var(--text-light);
    font-weight: 400;
    display: block;
    margin-top: 8px;
}

.quiz-result .btn {
    margin: 8px;
}

/* === Tones === */
.tones-content {
    max-width: 900px;
}

.tone-intro {
    font-size: 16px;
    line-height: 1.8;
    margin-bottom: 32px;
    color: var(--text-light);
}

.tones-table-wrapper {
    overflow-x: auto;
    margin-bottom: 32px;
}

.tones-table {
    width: 100%;
    border-collapse: collapse;
    background: var(--bg-card);
    border-radius: var(--radius);
    overflow: hidden;
    box-shadow: var(--shadow);
}

.tones-table th,
.tones-table td {
    padding: 14px 18px;
    text-align: left;
    border-bottom: 1px solid var(--border);
    font-size: 14px;
}

.tones-table th {
    background: var(--primary);
    color: white;
    font-weight: 600;
    font-size: 13px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.tones-table tr:hover {
    background: rgba(192, 57, 43, 0.03);
}

.tones-table tr:last-child td {
    border-bottom: none;
}

.tone-tips {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 28px;
}

.tone-tips h3 {
    color: var(--primary);
    margin-bottom: 16px;
    font-size: 18px;
}

.tone-tips ul {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.tone-tips li {
    font-size: 15px;
    line-height: 1.6;
    padding-left: 20px;
    position: relative;
}

.tone-tips li::before {
    content: "•";
    color: var(--primary);
    font-weight: 700;
    position: absolute;
    left: 0;
}

/* === About === */
.about-content {
    max-width: 750px;
    line-height: 1.8;
}

.about-content h2 {
    font-size: 22px;
    margin: 32px 0 12px;
    color: var(--primary);
}

.about-content h2:first-child {
    margin-top: 0;
}

.about-content p {
    margin-bottom: 16px;
    color: var(--text-light);
}

.about-content ul {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 10px;
    margin-bottom: 16px;
}

.about-content li {
    padding-left: 20px;
    position: relative;
    color: var(--text-light);
}

.about-content li::before {
    content: "•";
    color: var(--primary);
    font-weight: 700;
    position: absolute;
    left: 0;
}

/* === Footer === */
footer {
    text-align: center;
    padding: 24px;
    color: var(--text-muted);
    font-size: 13px;
    border-top: 1px solid var(--border);
}

/* === Audio Status === */
.audio-status {
    text-align: center;
    padding: 10px 20px;
    border-radius: var(--radius-sm);
    font-size: 14px;
    margin-bottom: 40px;
}

.audio-status-ok {
    background: rgba(39, 174, 96, 0.1);
    color: #27ae60;
    border: 1px solid rgba(39, 174, 96, 0.2);
}

.audio-status-fallback {
    background: rgba(243, 156, 18, 0.1);
    color: #b8860b;
    border: 1px solid rgba(243, 156, 18, 0.2);
}

.audio-status a {
    color: var(--primary);
    text-decoration: underline;
}

/* === Speaker Buttons === */
.speak-btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 36px;
    height: 36px;
    border-radius: 50%;
    border: 1px solid var(--border);
    background: var(--bg-card);
    color: var(--primary);
    cursor: pointer;
    transition: var(--transition);
    flex-shrink: 0;
    padding: 0;
}

.speak-btn:hover {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
    transform: scale(1.1);
}

.speak-btn:active {
    transform: scale(0.95);
}

.speak-btn-light {
    background: rgba(255, 255, 255, 0.2);
    border-color: rgba(255, 255, 255, 0.3);
    color: white;
}

.speak-btn-light:hover {
    background: rgba(255, 255, 255, 0.35);
    color: white;
    border-color: rgba(255, 255, 255, 0.5);
}

.speak-btn-large {
    width: 64px;
    height: 64px;
}

.speak-btn-large svg {
    width: 32px;
    height: 32px;
}

/* Speaker in vocab cards */
.vc-top-row {
    display: flex;
    justify-content: flex-end;
    margin-bottom: 4px;
}

/* Speaker in daily word */
.word-spotlight .hanzi {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 12px;
}

/* Vietnamese phonetic guide */
.vc-viet-phonetic {
    font-size: 14px;
    color: var(--primary);
    margin-bottom: 6px;
    padding: 4px 0;
}

.word-spotlight .viet-phonetic {
    font-size: 16px;
    opacity: 0.9;
    margin-bottom: 8px;
}

/* Quiz listen button */
.qq-listen-btn {
    display: flex;
    justify-content: center;
    margin: 16px 0;
}

/* Audio tooltip */
.audio-tooltip {
    position: fixed;
    bottom: 24px;
    left: 50%;
    transform: translateX(-50%);
    background: var(--bg-dark);
    color: white;
    padding: 10px 20px;
    border-radius: var(--radius-sm);
    font-size: 14px;
    z-index: 1000;
    animation: tooltipFade 2.5s ease forwards;
}

@keyframes tooltipFade {
    0% { opacity: 0; transform: translateX(-50%) translateY(10px); }
    15% { opacity: 1; transform: translateX(-50%) translateY(0); }
    80% { opacity: 1; }
    100% { opacity: 0; }
}

/* About steps */
.about-steps {
    list-style: decimal;
    padding-left: 24px;
    margin-bottom: 16px;
}

.about-steps li {
    padding-left: 8px;
    margin-bottom: 8px;
    color: var(--text-light);
}

.about-steps li::before {
    content: none;
}

.about-content code {
    background: rgba(192, 57, 43, 0.08);
    padding: 2px 8px;
    border-radius: 4px;
    font-size: 13px;
    color: var(--primary-dark);
}

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

/* === Responsive === */
@media (max-width: 768px) {
    .menu-toggle {
        display: flex;
    }

    nav {
        display: none;
        position: absolute;
        top: 64px;
        left: 0;
        right: 0;
        background: white;
        flex-direction: column;
        padding: 16px;
        border-bottom: 1px solid var(--border);
        box-shadow: var(--shadow);
    }

    nav.open {
        display: flex;
    }

    .nav-btn {
        text-align: left;
        padding: 12px 16px;
    }

    .hero h1 {
        font-size: 28px;
    }

    .hero-sub {
        font-size: 15px;
    }

    .page {
        padding: 24px 16px 60px;
    }

    .page-header h1 {
        font-size: 26px;
    }

    .vocab-cards {
        grid-template-columns: 1fr;
    }

    .quiz-answers {
        grid-template-columns: 1fr;
    }

    .word-spotlight {
        padding: 28px 20px;
    }

    .word-spotlight .hanzi {
        font-size: 42px;
    }

    .tones-table th,
    .tones-table td {
        padding: 10px 12px;
        font-size: 13px;
    }
}

@media (max-width: 480px) {
    .hero {
        padding: 30px 10px 30px;
    }

    .hero h1 {
        font-size: 24px;
    }

    .features {
        gap: 16px;
    }

    .category-grid {
        grid-template-columns: 1fr 1fr;
        gap: 12px;
    }

    .category-card {
        padding: 20px 16px;
    }

    .category-card .cat-icon {
        font-size: 28px;
    }

    .logo-text {
        font-size: 15px;
    }
}