/* SciLearn - Eye-friendly Science Learning Platform */
:root {
    /* Light Mode - Soft eye-friendly */
    --bg-primary: #f7f5f0;
    --bg-secondary: #ffffff;
    --bg-card: #ffffff;
    --text-primary: #2c2c2c;
    --text-secondary: #5a5a5a;
    --accent: #2a6f6f;
    --accent-hover: #1e5555;
    --border: #e0dcd3;
    --success: #3d7a4a;
    --warning: #b8860b;
    --danger: #a33b3b;
    --shadow: 0 2px 12px rgba(0,0,0,0.06);
    --radius: 12px;
    --header-h: 60px;
}

body.dark-mode {
    --bg-primary: #1a1d21;
    --bg-secondary: #242830;
    --bg-card: #2a2e36;
    --text-primary: #e8e6e1;
    --text-secondary: #a8a69f;
    --accent: #5cb8b8;
    --accent-hover: #7dcece;
    --border: #3a3f48;
    --success: #6bc77a;
    --warning: #e0b84a;
    --danger: #e06a6a;
    --shadow: 0 2px 12px rgba(0,0,0,0.3);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Sarabun', -apple-system, BlinkMacSystemFont, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.65;
    min-height: 100vh;
    transition: background 0.3s, color 0.3s;
    font-size: 16px;
}

/* Header */
.header {
    position: sticky;
    top: 0;
    z-index: 1000;
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border);
    box-shadow: var(--shadow);
}

.header-inner {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 16px;
    height: var(--header-h);
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
}

.logo {
    display: flex;
    align-items: center;
    gap: 8px;
    cursor: pointer;
    font-weight: 700;
    font-size: 1.25rem;
    color: var(--accent);
}

.logo-icon { font-size: 1.5rem; }

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

.nav-link {
    padding: 8px 14px;
    border-radius: 8px;
    text-decoration: none;
    color: var(--text-secondary);
    font-weight: 500;
    font-size: 0.95rem;
    transition: all 0.2s;
}

.nav-link:hover,
.nav-link.active {
    background: var(--accent);
    color: #fff;
}

.header-actions {
    display: flex;
    align-items: center;
    gap: 10px;
}

.theme-btn {
    background: var(--bg-primary);
    border: 1px solid var(--border);
    border-radius: 50%;
    width: 40px;
    height: 40px;
    font-size: 1.2rem;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: transform 0.2s;
}

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

.user-badge {
    background: var(--bg-primary);
    padding: 6px 12px;
    border-radius: 20px;
    font-size: 0.9rem;
    color: var(--text-secondary);
    max-width: 120px;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

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

.menu-toggle span {
    width: 22px;
    height: 2px;
    background: var(--text-primary);
    border-radius: 2px;
    transition: 0.3s;
}

/* Main */
.main-content {
    max-width: 1100px;
    margin: 0 auto;
    padding: 24px 16px 60px;
}

.page {
    display: none;
    animation: fadeIn 0.3s ease;
}

.page.active {
    display: block;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(8px); }
    to { opacity: 1; transform: translateY(0); }
}

.page-title {
    font-size: 1.75rem;
    font-weight: 700;
    margin-bottom: 8px;
    color: var(--accent);
}

.page-desc {
    color: var(--text-secondary);
    margin-bottom: 24px;
}

/* Hero */
.hero {
    text-align: center;
    padding: 40px 20px;
    background: var(--bg-card);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    margin-bottom: 32px;
}

.hero h1 {
    font-size: 1.9rem;
    margin-bottom: 12px;
    color: var(--accent);
}

.hero-sub {
    color: var(--text-secondary);
    margin-bottom: 24px;
    font-size: 1.05rem;
}

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

/* Buttons */
.btn {
    padding: 10px 20px;
    border-radius: 8px;
    border: none;
    font-family: inherit;
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
    display: inline-flex;
    align-items: center;
    gap: 6px;
}

.btn-primary {
    background: var(--accent);
    color: #fff;
}

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

.btn-outline {
    background: transparent;
    border: 1.5px solid var(--accent);
    color: var(--accent);
}

.btn-outline:hover {
    background: var(--accent);
    color: #fff;
}

.btn-success {
    background: var(--success);
    color: #fff;
}

.btn-lg {
    padding: 14px 28px;
    font-size: 1.1rem;
}

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

/* Features */
.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 16px;
    margin-bottom: 40px;
}

.feature-card {
    background: var(--bg-card);
    padding: 24px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    text-align: center;
}

.feature-icon {
    font-size: 2.2rem;
    margin-bottom: 12px;
}

.feature-card h3 {
    font-size: 1.15rem;
    margin-bottom: 8px;
}

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

/* Quick Start */
.quick-start h2 {
    margin-bottom: 16px;
    font-size: 1.3rem;
}

.quick-cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 12px;
}

.quick-card {
    background: var(--bg-card);
    padding: 16px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    display: flex;
    align-items: center;
    gap: 14px;
    cursor: pointer;
    transition: transform 0.2s, box-shadow 0.2s;
}

.quick-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(0,0,0,0.1);
}

.q-icon { font-size: 1.8rem; }

.quick-card strong { display: block; }
.quick-card small { color: var(--text-secondary); font-size: 0.85rem; }

/* Subject Tabs */
.subject-tabs {
    display: flex;
    gap: 8px;
    margin-bottom: 24px;
    flex-wrap: wrap;
}

.tab-btn {
    padding: 10px 18px;
    border-radius: 20px;
    border: 1.5px solid var(--border);
    background: var(--bg-card);
    color: var(--text-secondary);
    font-family: inherit;
    font-size: 0.95rem;
    cursor: pointer;
    transition: all 0.2s;
}

.tab-btn.active,
.tab-btn:hover {
    background: var(--accent);
    color: #fff;
    border-color: var(--accent);
}

/* Chapter List */
.chapter-list {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.chapter-item {
    background: var(--bg-card);
    border-radius: var(--radius);
    padding: 18px 20px;
    box-shadow: var(--shadow);
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    cursor: pointer;
    transition: transform 0.15s;
}

.chapter-item:hover {
    transform: translateX(4px);
}

.chapter-info h3 {
    font-size: 1.1rem;
    margin-bottom: 4px;
}

.chapter-info p {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.chapter-status {
    font-size: 0.85rem;
    padding: 4px 10px;
    border-radius: 12px;
    background: var(--bg-primary);
    color: var(--text-secondary);
    white-space: nowrap;
}

.chapter-status.done {
    background: rgba(61, 122, 74, 0.15);
    color: var(--success);
}

/* Lesson */
.lesson-header {
    margin-bottom: 24px;
}

.btn-back {
    background: none;
    border: none;
    color: var(--accent);
    font-family: inherit;
    font-size: 1rem;
    cursor: pointer;
    margin-bottom: 12px;
    padding: 4px 0;
}

.lesson-meta {
    display: flex;
    gap: 16px;
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-top: 8px;
}

.lesson-body {
    background: var(--bg-card);
    padding: 28px 24px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    margin-bottom: 24px;
}

.lesson-body h2 {
    color: var(--accent);
    margin: 28px 0 12px;
    font-size: 1.35rem;
}

.lesson-body h2:first-child { margin-top: 0; }

.lesson-body h3 {
    margin: 20px 0 10px;
    font-size: 1.15rem;
}

.lesson-body p {
    margin-bottom: 14px;
}

.lesson-body ul, .lesson-body ol {
    margin: 12px 0 16px 24px;
}

.lesson-body li {
    margin-bottom: 6px;
}

.example-box {
    background: var(--bg-primary);
    border-left: 4px solid var(--accent);
    padding: 16px 18px;
    border-radius: 0 8px 8px 0;
    margin: 16px 0;
}

.example-box .ex-title {
    font-weight: 600;
    color: var(--accent);
    margin-bottom: 8px;
}

.img-wrapper {
    text-align: center;
    margin: 20px 0;
}

.img-wrapper img {
    max-width: 100%;
    border-radius: 8px;
    box-shadow: var(--shadow);
}

.img-caption {
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-top: 8px;
}

.formula {
    background: var(--bg-primary);
    padding: 12px 16px;
    border-radius: 8px;
    text-align: center;
    font-size: 1.1rem;
    margin: 14px 0;
    font-family: 'Courier New', monospace;
}

.lesson-actions {
    text-align: center;
}

/* Quiz */
.quiz-header {
    margin-bottom: 20px;
}

.quiz-progress {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-top: 8px;
}

.progress-bar {
    flex: 1;
    height: 8px;
    background: var(--border);
    border-radius: 4px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: var(--accent);
    width: 0%;
    transition: width 0.3s;
}

.quiz-container {
    background: var(--bg-card);
    padding: 24px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    margin-bottom: 20px;
}

.question-text {
    font-size: 1.15rem;
    font-weight: 500;
    margin-bottom: 20px;
}

.options {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.option {
    padding: 14px 16px;
    border: 1.5px solid var(--border);
    border-radius: 10px;
    cursor: pointer;
    transition: all 0.2s;
    background: var(--bg-primary);
}

.option:hover {
    border-color: var(--accent);
}

.option.selected {
    border-color: var(--accent);
    background: rgba(42, 111, 111, 0.1);
}

.option.correct {
    border-color: var(--success);
    background: rgba(61, 122, 74, 0.15);
}

.option.wrong {
    border-color: var(--danger);
    background: rgba(163, 59, 59, 0.12);
}

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

.quiz-result {
    background: var(--bg-card);
    padding: 28px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    text-align: center;
    margin-top: 20px;
}

.quiz-result h2 {
    margin-bottom: 12px;
}

.score-big {
    font-size: 3rem;
    font-weight: 700;
    color: var(--accent);
    margin: 16px 0;
}

.explanation-box {
    text-align: left;
    margin-top: 20px;
    padding: 16px;
    background: var(--bg-primary);
    border-radius: 8px;
}

.explanation-box h4 {
    margin-bottom: 8px;
    color: var(--danger);
}

/* Stats */
.stats-overview {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
    gap: 12px;
    margin-bottom: 28px;
}

.stat-card {
    background: var(--bg-card);
    padding: 20px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    text-align: center;
}

.stat-value {
    font-size: 1.8rem;
    font-weight: 700;
    color: var(--accent);
}

.stat-label {
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-top: 4px;
}

.progress-list {
    margin-bottom: 24px;
}

.progress-item {
    background: var(--bg-card);
    padding: 14px 18px;
    border-radius: 10px;
    margin-bottom: 10px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: var(--shadow);
}

/* Games */
.games-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 16px;
    margin-bottom: 24px;
}

.game-card {
    background: var(--bg-card);
    padding: 28px 20px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    text-align: center;
    cursor: pointer;
    transition: transform 0.2s;
}

.game-card:hover {
    transform: translateY(-4px);
}

.game-icon {
    font-size: 2.5rem;
    margin-bottom: 12px;
}

.game-area {
    background: var(--bg-card);
    padding: 24px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    min-height: 300px;
}

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

.match-card {
    padding: 16px;
    background: var(--bg-primary);
    border: 2px solid var(--border);
    border-radius: 10px;
    cursor: pointer;
    text-align: center;
    transition: all 0.2s;
}

.match-card.selected {
    border-color: var(--accent);
    background: rgba(42, 111, 111, 0.15);
}

.match-card.matched {
    border-color: var(--success);
    background: rgba(61, 122, 74, 0.2);
    pointer-events: none;
}

.game-toolbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 12px;
    margin-bottom: 12px;
    flex-wrap: wrap;
}

.game-set-btns {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 12px;
}

.game-status {
    font-weight: 600;
    margin: 12px 0;
    color: var(--text-secondary);
}

.game-win {
    text-align: center;
    padding: 24px 12px;
    margin-top: 16px;
}

.race-q {
    font-size: 1.15rem;
    font-weight: 600;
    margin: 20px 0 16px;
    line-height: 1.5;
}

.race-opts {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.race-opt {
    width: 100%;
    text-align: left;
    padding: 14px 16px;
}

.periodic-sym {
    font-size: 3.5rem;
    font-weight: 800;
    text-align: center;
    margin: 20px 0 8px;
    color: var(--accent);
    letter-spacing: 0.05em;
}

.hint {
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.tf-btns {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 12px;
    margin-top: 16px;
}

.tf-btn {
    padding: 20px;
    font-size: 1.2rem;
}

.btn-sm {
    padding: 6px 12px;
    font-size: 0.85rem;
}

.btn-danger {
    background: #c0392b;
    color: #fff;
    border: none;
}

.btn-danger:hover {
    filter: brightness(1.08);
}

.btn-success {
    background: var(--success, #3d7a4a);
    color: #fff;
    border: none;
}

/* Certificate */
.cert-status {
    text-align: center;
    padding: 40px 20px;
    background: var(--bg-card);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
}

.cert-preview {
    margin-top: 20px;
}

.certificate {
    background: #fff;
    color: #222;
    max-width: 700px;
    margin: 0 auto 20px;
    padding: 20px;
}

.cert-border {
    border: 8px double #2a6f6f;
    padding: 40px 30px;
    text-align: center;
}

.cert-header h2 {
    font-size: 1.6rem;
    color: #2a6f6f;
    margin: 12px 0 4px;
}

.cert-sub {
    color: #666;
    font-style: italic;
}

.cert-body {
    margin: 30px 0;
}

.cert-body h1 {
    font-size: 2rem;
    color: #1a1a1a;
    margin: 16px 0;
    border-bottom: 2px solid #2a6f6f;
    display: inline-block;
    padding-bottom: 4px;
}

.cert-date {
    margin-top: 20px;
    color: #555;
}

.cert-footer {
    margin-top: 30px;
}

.sign-line {
    width: 180px;
    height: 1px;
    background: #333;
    margin: 0 auto 8px;
}

.cert-actions {
    text-align: center;
    display: flex;
    gap: 12px;
    justify-content: center;
}

/* Modal */
.modal {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.5);
    z-index: 2000;
    align-items: center;
    justify-content: center;
    padding: 20px;
}

.modal.show {
    display: flex;
}

.modal-content {
    background: var(--bg-card);
    padding: 28px;
    border-radius: var(--radius);
    max-width: 400px;
    width: 100%;
    box-shadow: 0 10px 40px rgba(0,0,0,0.2);
}

.modal-content h2 {
    margin-bottom: 8px;
}

.modal-content p {
    color: var(--text-secondary);
    margin-bottom: 16px;
    font-size: 0.95rem;
}

.modal-content input {
    width: 100%;
    padding: 12px 14px;
    border: 1.5px solid var(--border);
    border-radius: 8px;
    font-family: inherit;
    font-size: 1rem;
    background: var(--bg-primary);
    color: var(--text-primary);
    margin-bottom: 20px;
}

.modal-actions {
    display: flex;
    gap: 10px;
    justify-content: flex-end;
}

/* Footer */
.footer {
    text-align: center;
    padding: 24px 16px;
    color: var(--text-secondary);
    font-size: 0.85rem;
    border-top: 1px solid var(--border);
}

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

    .nav {
        display: none;
        position: absolute;
        top: var(--header-h);
        left: 0;
        right: 0;
        background: var(--bg-secondary);
        flex-direction: column;
        padding: 12px;
        border-bottom: 1px solid var(--border);
        box-shadow: var(--shadow);
    }

    .nav.open {
        display: flex;
    }

    .nav-link {
        padding: 12px 16px;
    }

    .user-badge {
        display: none;
    }

    .hero h1 {
        font-size: 1.5rem;
    }

    .lesson-body {
        padding: 20px 16px;
    }

    .match-grid {
        grid-template-columns: 1fr;
    }

    .cert-border {
        padding: 24px 16px;
    }

    .cert-body h1 {
        font-size: 1.5rem;
    }
}

/* Print */
@media print {
    .header, .footer, .cert-actions, .btn-back, .nav {
        display: none !important;
    }
    .certificate {
        box-shadow: none;
    }
}