/* ============================================================
   MFM course website - design system (same as SFM / TSA sites)
   ============================================================ */
:root {
    --main-blue: #1A3A6E;
    --accent-blue: #2A528C;
    --ida-red: #DC3545;
    --forest: #2E7D32;
    --amber: #B5853F;
    --dark-gray: #333;
    --mid-gray: #777;
    --light-gray: #f5f5f5;
    --border: #ddd;
    --white: #ffffff;
}

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

html, body { overflow-x: hidden; }
.info-card, .formula-card, .chapter-card, .quiz-question, .resource-item { min-width: 0; }
mjx-container[display="true"] { max-width: 100%; overflow-x: auto; overflow-y: hidden; }
.header-title, .header-title p { overflow-wrap: anywhere; }

html { scroll-behavior: smooth; scroll-padding-top: 70px; }

body {
    font-family: 'Inter', 'Segoe UI', system-ui, -apple-system, sans-serif;
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    color: var(--dark-gray);
    background: var(--white);
}

a { color: var(--main-blue); }

/* ---------------- HEADER ---------------- */
header {
    background: linear-gradient(135deg, var(--main-blue) 0%, var(--accent-blue) 100%);
    color: white;
    padding: 2rem 0;
    text-align: center;
}

.header-inner {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 1rem;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
}

.header-logo {
    height: 60px;
    background: white;
    padding: 5px;
    border-radius: 4px;
}

.header-title { flex: 1; }
header h1 { font-family: 'Source Serif 4', Georgia, serif; font-size: 2.6rem; letter-spacing: -0.01em; margin-bottom: 0.5rem; }
header p { font-size: 1.1rem; opacity: 0.9; }

/* ---------------- NAVIGATION ---------------- */
nav {
    background: var(--dark-gray);
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 100;
}

nav ul {
    list-style: none;
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 2rem;
    max-width: 1200px;
    margin: 0 auto;
}

nav a {
    color: white;
    text-decoration: none;
    font-weight: 500;
    padding: 0.5rem 1rem;
    border-radius: 4px;
    transition: background 0.3s;
}

nav a:hover { background: var(--main-blue); }

.lang-switcher { display: flex; align-items: center; gap: 0.5rem; margin-left: auto; padding-left: 2rem; }

.lang-btn {
    padding: 0.4rem 0.8rem !important;
    border: 2px solid white;
    border-radius: 4px;
    font-weight: bold;
    font-size: 0.9rem;
}

.lang-btn:hover { background: white; color: var(--dark-gray); }
.lang-btn.active { background: white; color: var(--main-blue); }

/* ---------------- MAIN ---------------- */
main { max-width: 1200px; margin: 0 auto; padding: 2rem; }
section { margin-bottom: 3rem; }

h2 {
    font-family: 'Source Serif 4', Georgia, serif;
    font-size: 1.9rem;
    letter-spacing: -0.01em;
    color: var(--main-blue);
    border-bottom: 3px solid var(--ida-red);
    padding-bottom: 0.5rem;
    margin-bottom: 1.5rem;
}

h3.sub { color: var(--main-blue); margin: 2rem 0 1rem; }

/* ---------------- INFO CARDS ---------------- */
.course-info {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(min(210px, 100%), 1fr));
    gap: 1.5rem;
    margin-bottom: 2rem;
}

.info-card {
    background: var(--light-gray);
    padding: 1.5rem;
    border-radius: 8px;
    border-left: 4px solid var(--main-blue);
    overflow-x: auto;
}

.info-card h3 { color: var(--main-blue); margin-bottom: 0.5rem; font-size: 1rem; }
.info-card p { overflow-wrap: break-word; font-size: 0.95rem; }

.objectives { list-style: none; }
.objectives li { padding: 0.3rem 0 0.3rem 1.5rem; position: relative; }
.objectives li::before { content: ">"; color: var(--ida-red); position: absolute; left: 0; font-weight: bold; }

.formula-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(min(480px, 100%), 1fr));
    gap: 1rem;
}

.formula-card {
    display: flex;
    flex-direction: column;
    background: white;
    border: 1px solid #e3e7ee;
    border-top: 3px solid var(--main-blue);
    border-radius: 10px;
    padding: 0.9rem 1.1rem 0.8rem;
    overflow-x: auto;
    box-shadow: 0 1px 2px rgba(16, 36, 70, 0.04);
    transition: box-shadow 0.2s, transform 0.2s;
}
.formula-card:hover { box-shadow: 0 8px 24px rgba(16, 36, 70, 0.10); transform: translateY(-2px); }
.formula-card[hidden] { display: none; }
.formula-head { display: flex; flex-direction: column-reverse; gap: 0.15rem; }
.formula-card h4 { color: var(--main-blue); font-size: 0.95rem; font-weight: 700; }
.formula-group { font-size: 0.7rem; text-transform: uppercase; letter-spacing: 0.06em; color: var(--ida-red); white-space: nowrap; font-weight: 600; }
.formula-tex { flex: 1; display: flex; align-items: center; justify-content: center; min-height: 4.5rem; font-size: 0.92rem; max-width: 100%; overflow-x: auto; }
.formula-link { align-self: flex-end; font-size: 0.8rem; font-weight: 600; text-decoration: none; color: var(--accent-blue); }
.formula-link:hover { text-decoration: underline; }

/* ---------------- CHAPTER CARDS ---------------- */
.chapters-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(min(300px, 100%), 1fr));
    gap: 1.5rem;
}

.chapter-card {
    background: white;
    border: 1px solid var(--border);
    border-radius: 8px;
    overflow: hidden;
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
    transition: transform 0.3s, box-shadow 0.3s;
    display: flex;
    flex-direction: column;
}

.chapter-card:hover { transform: translateY(-5px); box-shadow: 0 8px 25px rgba(0,0,0,0.15); }

.chapter-header {
    background: var(--main-blue);
    color: white;
    padding: 1rem;
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    gap: 0.5rem;
}

.chapter-card.soon .chapter-header { background: #5b6b85; }
.chapter-header h3 { margin: 0; font-size: 1.1rem; }

.badge {
    flex-shrink: 0;
    font-size: 0.72rem;
    font-weight: 600;
    padding: 0.2rem 0.5rem;
    border-radius: 10px;
    white-space: nowrap;
}

.badge-soon { background: rgba(255,255,255,0.2); color: white; border: 1px solid rgba(255,255,255,0.6); }
.badge-live { background: var(--forest); color: white; }
.badge-self { background: var(--ida-red); color: white; }
.chapter-header .badges { display: flex; flex-wrap: wrap; gap: 0.3rem; justify-content: flex-end; }
.quiz-tabs .tab-badge { display: inline-block; margin-left: 0.3rem; padding: 0 0.35rem; border-radius: 3px;
    background: var(--ida-red); color: white; font-size: 0.7rem; font-weight: 600; vertical-align: middle; }

.chapter-body { padding: 1.5rem; display: flex; flex-direction: column; flex: 1; }
.chapter-body ul { list-style: none; margin-bottom: 1rem; }
.chapter-body li { padding: 0.3rem 0 0.3rem 1.5rem; position: relative; }
.chapter-body li::before { content: ">"; color: var(--ida-red); position: absolute; left: 0; font-weight: bold; }

.chapter-links { display: flex; flex-wrap: wrap; gap: 0.5rem; margin-top: auto; }
.link-group { display: inline-flex; gap: 0; }
.link-group .btn:first-child { border-top-right-radius: 0; border-bottom-right-radius: 0; }
.link-group .btn-colab { border-top-left-radius: 0; border-bottom-left-radius: 0; }

.quantinar-box {
    margin-top: 1rem;
    padding-top: 0.8rem;
    border-top: 1px dashed var(--border);
    font-size: 0.85rem;
}

.quantinar-box h4 {
    display: flex;
    align-items: center;
    gap: 0.4rem;
    color: var(--main-blue);
    font-size: 0.85rem;
    margin-bottom: 0.3rem;
}

.quantinar-box h4 img { height: 18px; }
.chapter-body .quantinar-box ul { margin-bottom: 0; }
.chapter-body .quantinar-box li { padding: 0.1rem 0 0.1rem 1rem; }
.chapter-body .quantinar-box li::before { content: "\203A"; color: var(--main-blue); }
.quantinar-box a { text-decoration: none; }
.quantinar-box a:hover { text-decoration: underline; }

/* ---------------- BUTTONS ---------------- */
.btn {
    display: inline-block;
    padding: 0.5rem 1rem;
    border-radius: 4px;
    text-decoration: none;
    font-size: 0.9rem;
    border: none;
    cursor: pointer;
    font-family: inherit;
    transition: background 0.3s;
}

.btn-primary { background: var(--main-blue); color: white; }
.btn-primary:hover { background: var(--accent-blue); }
.btn-secondary { background: var(--forest); color: white; }
.btn-secondary:hover { background: #1b5e20; }
.btn-outline { border: 2px solid var(--main-blue); color: var(--main-blue); background: white; }
.btn-outline:hover, .btn-outline.active { background: var(--main-blue); color: white; }
.btn-colab { background: #F9AB00; color: #333; }
.btn-colab:hover { background: #E09600; }

.btn.disabled {
    background: #eee;
    color: #999;
    border: 1px dashed #bbb;
    cursor: not-allowed;
    pointer-events: none;
}

.btn:focus-visible, nav a:focus-visible, .quiz-options li:focus-visible {
    outline: 3px solid #F9AB00;
    outline-offset: 2px;
}

/* ---------------- QUIZ ---------------- */
.quiz-tabs { display: flex; flex-wrap: wrap; gap: 0.5rem; margin-bottom: 1.5rem; }
.quiz-tabs .btn { padding: 0.35rem 0.7rem; }
.quiz-tabs .btn.unavailable { border-style: dashed; color: #888; border-color: #aaa; }
.quiz-tabs .btn.unavailable.active { background: #888; color: white; }

#github-login {
    margin-bottom: 1.5rem;
    padding: 1rem;
    background: var(--light-gray);
    border-radius: 8px;
}

#github-login p { margin-bottom: 0.5rem; }

.quiz-container { background: var(--light-gray); padding: 2rem; border-radius: 8px; }
.quiz-container > h3 { color: var(--main-blue); margin-bottom: 0.5rem; }
.quiz-intro { font-size: 0.9rem; color: #555; margin-bottom: 1.5rem; }

.quiz-question {
    background: white;
    padding: 1.5rem;
    border-radius: 8px;
    margin-bottom: 1.5rem;
    border-left: 4px solid var(--main-blue);
}

.quiz-question h4 { color: var(--main-blue); margin-bottom: 0.6rem; }
.quiz-question > p { margin-bottom: 0.6rem; }

.quiz-options { list-style: none; }

.quiz-options li {
    padding: 0.5rem;
    margin: 0.3rem 0;
    cursor: pointer;
    border-radius: 4px;
    transition: background 0.3s;
}

.quiz-options li:hover { background: #e3f2fd; }
.quiz-options li.locked { pointer-events: none; opacity: 0.7; }
.quiz-options li.chosen { opacity: 1; font-weight: 600; }
.quiz-options input[type="radio"] { margin-right: 0.5rem; }

.answer-reveal { display: none; padding: 1rem; margin-top: 1rem; border-radius: 4px; }
.answer-correct { background: #c8e6c9; border-left: 4px solid var(--forest); }
.answer-incorrect { background: #ffcdd2; border-left: 4px solid var(--ida-red); }

.quiz-actions { margin-top: 1.5rem; display: flex; flex-wrap: wrap; gap: 0.5rem; }
.score-display { margin-top: 1rem; font-weight: bold; font-size: 1.1rem; }

.answer-key {
    margin-top: 1.5rem;
    padding: 1.5rem;
    background: #f8f9fa;
    border-radius: 8px;
    border: 1px solid #dee2e6;
    overflow-x: auto;
}

.answer-key h4 { margin-bottom: 0.8rem; color: var(--main-blue); }
.answer-key table { width: 100%; border-collapse: collapse; font-size: 0.85rem; }
.answer-key th { background: var(--main-blue); color: white; }
.answer-key th, .answer-key td { padding: 0.35rem 0.6rem; border: 1px solid #dee2e6; text-align: left; vertical-align: top; }
.answer-key td.c { text-align: center; }
.answer-key tr.ok { background: #e8f5e9; }
.answer-key tr.ko { background: #ffebee; }
.answer-key .res-ok { color: var(--forest); font-weight: bold; }
.answer-key .res-ko { color: var(--ida-red); font-weight: bold; }

/* ---------------- RESOURCES ---------------- */
.resources-list {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(min(230px, 100%), 1fr));
    gap: 1rem;
}

.resource-item {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1rem;
    background: white;
    border-radius: 8px;
    border: 1px solid var(--border);
    text-decoration: none;
    color: var(--dark-gray);
    transition: background 0.3s;
}

.resource-item:hover { background: var(--light-gray); }
.resource-item p { font-size: 0.9rem; color: #555; }

.resource-icon {
    width: 40px;
    height: 40px;
    flex-shrink: 0;
    background: var(--main-blue);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 1.2rem;
}

.biblio { padding-left: 1.2rem; }
.biblio li { margin: 0.35rem 0; }
.data-sources { list-style: none; }
.data-sources li { padding: 0.25rem 0; }

/* ---------------- FOOTER ---------------- */
footer {
    background: var(--dark-gray);
    color: white;
    text-align: center;
    padding: 2rem;
    margin-top: 3rem;
}

.footer-logos {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 1rem;
    margin-bottom: 1rem;
}

.resource-logo { width: 40px; height: 40px; object-fit: contain; flex-shrink: 0; }
.footer-logos img { height: 44px; background: white; padding: 5px; border-radius: 4px; }
footer .muted { margin-top: 0.5rem; opacity: 0.8; font-size: 0.9rem; }

/* ---------------- RESPONSIVE ---------------- */
@media (max-width: 900px) {
    nav ul { gap: 0.3rem; flex-wrap: wrap; padding: 0 0.5rem; }
    .lang-switcher { margin-left: 0; padding-left: 0; }
}

@media (max-width: 768px) {
    main { padding: 1.5rem 1rem; }
    .header-inner { padding: 0 1rem; }
    .header-logo { height: 40px; }
    header h1 { font-size: 1.6rem; }
    header p { font-size: 0.9rem; }
    nav { padding: 0.5rem 0; }
    nav a { padding: 0.3rem 0.5rem; font-size: 0.9rem; }
    .chapters-grid, .formula-grid { grid-template-columns: 1fr; }
    .quiz-container { padding: 1rem; }
    .quiz-question { padding: 1rem; }
}

@media (max-width: 480px) {
    .header-logo { display: none; }
    .chapter-links .btn, .link-group { width: 100%; }
    .link-group .btn:first-child { flex: 1; }
}


/* ============================================================
   Showcase: hero, gallery, formula filters, lightbox
   ============================================================ */
nav { box-shadow: 0 2px 10px rgba(0, 0, 0, 0.15); }

.hero {
    background:
        radial-gradient(1200px 300px at 85% -40%, rgba(220, 53, 69, 0.20), transparent 60%),
        linear-gradient(180deg, #13294f 0%, #1A3A6E 100%);
    color: white;
    padding: 2.4rem 0 2.6rem;
}
.hero-inner { max-width: 1200px; margin: 0 auto; padding: 0 2rem; text-align: center; }
.hero-tag { font-size: 1.15rem; max-width: 820px; margin: 0 auto 1.8rem; opacity: 0.95; line-height: 1.55; }
.hero-stats {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(min(140px, 100%), 1fr));
    gap: 1rem;
    max-width: 1000px;
    margin: 0 auto 1.8rem;
}
.stat {
    background: rgba(255, 255, 255, 0.07);
    border: 1px solid rgba(255, 255, 255, 0.14);
    border-radius: 12px;
    padding: 0.9rem 0.6rem;
    display: flex; flex-direction: column; align-items: center;
}
.stat-num { font-family: 'Source Serif 4', Georgia, serif; font-size: 2rem; font-weight: 700; line-height: 1.1; }
.stat-label { font-size: 0.8rem; text-transform: uppercase; letter-spacing: 0.06em; opacity: 0.8; margin-top: 0.25rem; }
.hero-cta { display: flex; gap: 0.8rem; justify-content: center; flex-wrap: wrap; }
.btn-lg { padding: 0.75rem 1.4rem; font-size: 1rem; font-weight: 600; border-radius: 8px; }
.hero .btn-primary { background: white; color: var(--main-blue); }
.hero .btn-primary:hover { background: #e9eef7; }
.btn-ghost { border: 1.5px solid rgba(255, 255, 255, 0.7); color: white; background: transparent; }
.btn-ghost:hover { background: rgba(255, 255, 255, 0.12); }

.section-intro { color: #4a5568; max-width: 820px; margin: -0.4rem 0 1.2rem; }

.gallery {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(min(260px, 100%), 1fr));
    gap: 1.2rem;
    margin-bottom: 1rem;
}
.gallery-item {
    background: white;
    border: 1px solid #e3e7ee;
    border-radius: 12px;
    overflow: hidden;
    display: flex; flex-direction: column;
    box-shadow: 0 1px 2px rgba(16, 36, 70, 0.04);
    transition: box-shadow 0.2s, transform 0.2s;
}
.gallery-item:hover { box-shadow: 0 10px 28px rgba(16, 36, 70, 0.12); transform: translateY(-3px); }
.gallery-open {
    border: 0; background: white; cursor: zoom-in; padding: 0.6rem;
    aspect-ratio: 4 / 3; display: flex; align-items: center; justify-content: center;
}
.gallery-open img { max-width: 100%; max-height: 100%; object-fit: contain; }
.gallery-item figcaption {
    font-size: 0.85rem; padding: 0.6rem 0.9rem 0.8rem; border-top: 1px solid #eef1f5; color: #333; line-height: 1.4;
}
.gallery-item figcaption a { font-weight: 600; text-decoration: none; white-space: nowrap; }

.chip-row { display: flex; flex-wrap: wrap; gap: 0.5rem; margin-bottom: 1.1rem; }
.chip {
    font-family: inherit; font-size: 0.85rem; font-weight: 500;
    padding: 0.4rem 0.9rem; border-radius: 999px; cursor: pointer;
    border: 1px solid #cfd8e6; background: white; color: var(--main-blue);
    transition: background 0.2s, color 0.2s, border-color 0.2s;
}
.chip:hover { border-color: var(--main-blue); }
.chip.active { background: var(--main-blue); color: white; border-color: var(--main-blue); }

.lightbox {
    position: fixed; inset: 0; z-index: 1000;
    background: rgba(10, 20, 40, 0.85);
    display: flex; align-items: center; justify-content: center; padding: 2rem;
}
.lightbox[hidden] { display: none; }
.lightbox figure { background: white; border-radius: 12px; padding: 1rem; max-width: min(1200px, 100%); max-height: 100%; overflow: auto; }
.lightbox img { display: block; max-width: 100%; max-height: 78vh; margin: 0 auto; }
.lightbox figcaption { text-align: center; margin-top: 0.6rem; font-size: 0.95rem; color: #333; }
.lightbox-close {
    position: absolute; top: 1rem; right: 1.4rem; font-size: 2.2rem; line-height: 1;
    color: white; background: transparent; border: 0; cursor: pointer;
}
body.no-scroll { overflow: hidden; }

.chapter-card { transition: box-shadow 0.2s, transform 0.2s; }
.chapter-card:hover { box-shadow: 0 10px 28px rgba(16, 36, 70, 0.12); transform: translateY(-2px); }

@media (max-width: 768px) {
    .hero { padding: 1.6rem 0 1.8rem; }
    .hero-inner { padding: 0 1rem; }
    .hero-tag { font-size: 1rem; }
    .stat-num { font-size: 1.6rem; }
    header h1 { font-size: 1.8rem; }
    h2 { font-size: 1.5rem; }
}


/* ---------------- chapter card: chart + formulas ---------------- */
.chapter-chart {
    display: block; width: 100%; border: 0; border-bottom: 1px solid #eef1f5;
    background: white; padding: 0.6rem 0.8rem; cursor: zoom-in;
    aspect-ratio: 16 / 10;
}
.chapter-chart img { width: 100%; height: 100%; object-fit: contain; display: block; transition: transform 0.25s; }
.chapter-chart:hover img { transform: scale(1.02); }
.chapter-formulas {
    margin: 0.8rem 0 0.4rem;
    border: 1px solid #e3e7ee; border-radius: 8px; background: #fafbfd;
}
.chapter-formulas summary {
    cursor: pointer; padding: 0.5rem 0.8rem; font-weight: 600; font-size: 0.9rem; color: var(--main-blue);
    list-style: none;
}
.chapter-formulas summary::-webkit-details-marker { display: none; }
.chapter-formulas summary::before { content: '\25B8'; color: var(--ida-red); margin-right: 0.45rem; display: inline-block; transition: transform 0.2s; }
.chapter-formulas[open] summary::before { transform: rotate(90deg); }
.cf { padding: 0.4rem 0.8rem 0.6rem; border-top: 1px solid #eef1f5; }
.cf h5 { font-size: 0.8rem; color: var(--main-blue); margin-bottom: 0.2rem; }
.cf-tex { font-size: 0.78rem; overflow-x: auto; overflow-y: hidden; }

/* ---------------- quiz login (Google) ---------------- */
.quiz-login { background: #f4f7fc; border: 1px solid #dbe3f0; border-radius: 10px; padding: 1rem 1.2rem; margin-bottom: 1.2rem; }
.quiz-login p { margin-bottom: 0.6rem; }
.login-msg { color: var(--ida-red); font-size: 0.9rem; min-height: 1.2em; }
.save-status { font-size: 0.9rem; color: var(--forest); min-height: 1.2em; }

.hero-teachers { margin-top: 1rem; font-size: 0.85rem; opacity: 0.85; }
.hero-teachers a { color: white; text-decoration: underline; }
.hero-teachers[hidden] { display: none; }
.teacher-btn { background: none; border: 0; padding: 0; color: white; font: inherit; text-decoration: underline; cursor: pointer; }
.teacher-btn[hidden] { display: none; }
#teacher-g-button { display: inline-block; margin-top: 0.4rem; }