/* Quantify — стилі багатосторінкового сайту.
   Візуальний стиль збережено з попередньої версії; розмітка тепер статична. */

:root {
  --bg-color: #F8FAFC;
  --card-bg: #FFFFFF;
  --text-main: #0F172A;
  --text-muted: #64748B;
  --text-soft: #475569;
  --algebra-color: #2563EB;
  --algebra-bg: #DBEAFE;
  --geometry-color: #059669;
  --geometry-bg: #D1FAE5;
  --border-color: #E2E8F0;
  --border-radius: 12px;
}

*, *::before, *::after { box-sizing: border-box; }
* { margin: 0; padding: 0; }
[hidden] { display: none !important; }

html { -webkit-text-size-adjust: 100%; }
body {
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: var(--bg-color);
  color: var(--text-main);
  line-height: 1.5;
  overflow-x: hidden;
}
input, button, select, textarea { font-family: inherit; }
a { color: var(--algebra-color); }
img, svg { max-width: 100%; }
:focus-visible { outline: 2px solid var(--algebra-color); outline-offset: 2px; }
body.no-scroll { overflow: hidden; }

html.no-js .js-only { display: none !important; }
.sr-only, .skip-link:not(:focus) {
  position: absolute; width: 1px; height: 1px; margin: -1px; padding: 0;
  overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; border: 0;
}
.skip-link:focus {
  position: fixed; top: 8px; left: 8px; z-index: 100; background: #fff;
  padding: 10px 14px; border-radius: 8px; box-shadow: 0 4px 16px rgba(0,0,0,.2);
}

/* --- підказка про мову --- */
.lang-suggest {
  display: flex; flex-wrap: wrap; gap: 8px 14px; align-items: center; justify-content: center;
  background: #EFF6FF; border-bottom: 1px solid #BFDBFE; padding: 8px 16px; font-size: .9rem;
}
.lang-suggest button {
  background: none; border: 0; font-size: 1.3rem; line-height: 1; cursor: pointer; color: var(--text-soft); padding: 0 4px;
}

/* --- шапка --- */
.header {
  display: flex; justify-content: space-between; align-items: center; gap: 12px; flex-wrap: wrap;
  padding: 12px 32px; background: #fff; border-bottom: 1px solid var(--border-color);
}
.header-left { display: flex; align-items: center; gap: 12px; }
.header-actions { display: flex; align-items: center; gap: 12px; }
.logo {
  font-size: 1.6rem; font-weight: 800; color: var(--text-main); text-decoration: none; letter-spacing: -.5px;
}
.logo span { color: var(--algebra-color); }

.sidebar-toggle {
  display: none; align-items: center; justify-content: center; flex-shrink: 0;
  width: 40px; height: 40px; border: 1px solid var(--border-color); border-radius: 8px;
  background: #fff; color: var(--text-main); cursor: pointer;
}

.lang-switch { display: inline-flex; gap: 2px; padding: 3px; background: #E2E8F0; border-radius: 10px; }
.lang-switch a {
  padding: 6px 11px; border-radius: 8px; font-size: .85rem; font-weight: 700;
  color: var(--text-soft); text-decoration: none;
}
.lang-switch a:hover { color: var(--text-main); }
.lang-switch a[aria-current] { background: #fff; color: var(--text-main); box-shadow: 0 1px 3px rgba(0,0,0,.12); }

.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  padding: 10px 18px; font-size: .9rem; font-weight: 600; line-height: 1.2;
  border-radius: 8px; border: 1px solid transparent; cursor: pointer; text-decoration: none;
  transition: background .2s, border-color .2s;
}
.btn-primary { background: var(--algebra-color); color: #fff; }
.btn-primary:hover { background: #1D4ED8; }
.btn-outline { background: #fff; color: var(--text-main); border-color: #CBD5E1; }
.btn-outline:hover { border-color: var(--text-main); }
.btn-small { width: 100%; padding: 8px 0; font-size: .85rem; margin-top: 4px; }

/* --- каркас --- */
.app-container {
  display: flex; align-items: flex-start; gap: 32px;
  max-width: 1500px; margin: 0 auto; padding: 24px 32px;
}
.main-content { flex: 1 1 auto; min-width: 0; }

.sidebar {
  flex: 0 0 250px; width: 250px; background: #fff; border: 1px solid var(--border-color);
  border-radius: 16px; padding: 18px; position: sticky; top: 16px;
  max-height: calc(100vh - 32px); overflow-y: auto;
}
.sidebar-title { font-size: 1.05rem; font-weight: 700; margin-bottom: 12px; }
.topic-list { list-style: none; }
.topic-list-extra { margin-top: 12px; padding-top: 12px; border-top: 1px solid var(--border-color); }
.topic-item {
  display: block; padding: 9px 12px; border-radius: 10px; margin-bottom: 3px;
  font-size: .93rem; color: var(--text-soft); text-decoration: none;
}
.topic-item:hover { background: #F1F5F9; color: var(--text-main); }
.topic-item.active { background: var(--algebra-color); color: #fff; font-weight: 600; }

.sidebar-overlay { display: none; position: fixed; inset: 0; background: rgba(15,23,42,.45); z-index: 40; }
.sidebar-overlay.active { display: block; }

/* --- заголовок сторінки --- */
.hero { text-align: center; margin-bottom: 24px; }
.hero h1 { font-size: 2.1rem; font-weight: 800; letter-spacing: -.5px; line-height: 1.2; margin-bottom: 8px; }
.hero p { color: var(--text-muted); font-size: 1.05rem; }
.hero-left { text-align: left; margin-bottom: 20px; }
.topic-intro { max-width: 75ch; color: var(--text-soft) !important; line-height: 1.65; margin-bottom: 8px; }
.topic-meta { font-size: .9rem !important; font-weight: 600; color: var(--algebra-color) !important; }

.breadcrumbs { display: flex; flex-wrap: wrap; gap: 8px; font-size: .85rem; color: var(--text-muted); margin-bottom: 14px; }
.breadcrumbs a { text-decoration: none; }
.breadcrumbs a:hover { text-decoration: underline; }

/* --- пошук --- */
.search-row { display: flex; gap: 10px; align-items: stretch; max-width: 720px; margin: 0 0 24px; }
.search-row .search-box { flex: 1 1 auto; min-width: 0; max-width: none; margin: 0; }
.fav-link { flex: 0 0 auto; white-space: nowrap; display: inline-flex; align-items: center; padding: 0 12px; border: 1px solid var(--border, #d0d7de); border-radius: 12px; background: #fff; text-decoration: none; font-weight: 600; }
@media (max-width: 420px) { .fav-link { padding: 0 10px; font-size: 14px; } }
body[data-kind="home"] .search-row { margin-left: auto; margin-right: auto; }
.search-input {
  width: 100%; padding: 14px 18px; font-size: 16px; border: 2px solid var(--border-color);
  border-radius: var(--border-radius); background: #fff; outline: none;
  box-shadow: 0 4px 6px -1px rgba(0,0,0,.04); transition: border-color .2s, box-shadow .2s;
}
.search-input:focus { border-color: var(--algebra-color); box-shadow: 0 10px 15px -3px rgba(37,99,235,.12); }
.search-results {
  position: absolute; left: 0; right: 0; top: calc(100% + 6px); z-index: 30; list-style: none; padding: 6px;
  background: #fff; border: 1px solid var(--border-color); border-radius: 12px;
  box-shadow: 0 12px 30px rgba(15,23,42,.14); max-height: min(60vh, 420px); overflow-y: auto; text-align: left;
}
.search-results a {
  display: flex; flex-direction: column; gap: 1px; padding: 9px 12px; border-radius: 8px;
  color: var(--text-main); text-decoration: none;
}
.search-results a:hover, .search-results a:focus { background: #EFF6FF; }
.sr-title { font-weight: 600; }
.sr-meta { font-size: .8rem; color: var(--text-muted); }
.search-results .sr-empty { padding: 12px; color: var(--text-muted); }

/* --- фільтри та панель інструментів --- */
.toolbar, .filters { display: flex; flex-wrap: wrap; align-items: center; gap: 12px 16px; margin-bottom: 18px; }
.toolbar { justify-content: space-between; }
.view-toggle, .subject-toggle { display: inline-flex; gap: 4px; padding: 4px; background: #E2E8F0; border-radius: 10px; }
.view-btn, .subject-btn {
  padding: 8px 16px; border: 0; border-radius: 8px; background: transparent; cursor: pointer;
  font-size: .9rem; font-weight: 700; color: var(--text-soft); transition: background .2s;
}
.view-btn.active, .subject-btn.active-all { background: #fff; color: var(--text-main); box-shadow: 0 1px 3px rgba(0,0,0,.1); }
.subject-btn.active-algebra { background: var(--algebra-color); color: #fff; }
.subject-btn.active-geometry { background: var(--geometry-color); color: #fff; }
.class-selector { display: flex; flex-wrap: wrap; gap: 8px; }
.class-selector-left { justify-content: flex-start; }
.home-grades { max-width: 720px; margin: -8px auto 24px; display: flex; flex-wrap: wrap; align-items: center; gap: 8px 12px; }
.home-grades-label { font-weight: 600; font-size: .9rem; color: var(--text-muted, #57606a); }
.class-chip { text-decoration: none; }
.home-subjects { max-width: 720px; margin: -12px auto 24px; display: flex; flex-wrap: wrap; align-items: center; gap: 8px 12px; }
.class-chip {
  display: inline-block; padding: 6px 15px; border: 1px solid #CBD5E1; border-radius: 20px;
  background: #fff; cursor: pointer; font-size: .88rem; font-weight: 600; color: var(--text-soft);
  text-decoration: none; transition: background .2s, color .2s;
}
.class-chip:hover, .class-chip.active { background: var(--text-main); border-color: var(--text-main); color: #fff; }
.print-tip { flex-basis: 100%; font-size: .82rem; color: var(--text-muted); }

.toc { background: #fff; border: 1px solid var(--border-color); border-radius: var(--border-radius); padding: 12px 16px; margin-bottom: 20px; }
.toc summary { cursor: pointer; font-weight: 600; }
.toc ol { columns: 2 280px; column-gap: 28px; margin: 12px 0 0 22px; font-size: .92rem; }
.toc li { break-inside: avoid; padding: 2px 0; }

/* --- сітка та картки --- */
.grid {
  display: grid; align-items: start; gap: 20px; width: 100%;
  grid-template-columns: repeat(auto-fill, minmax(min(100%, 300px), 1fr));
}
.grid-compact { grid-template-columns: repeat(auto-fill, minmax(min(100%, 260px), 1fr)); gap: 14px; }
.card {
  position: relative; min-width: 0; max-width: 100%; background: var(--card-bg);
  border: 1px solid var(--border-color); border-radius: var(--border-radius); padding: 20px;
  box-shadow: 0 1px 3px rgba(0,0,0,.05); overflow-wrap: break-word; scroll-margin-top: 16px;
}
/* Вирівнювання рядків між сусідніми картками (заголовок / формула / опис не «з'їжджають») */
@supports (grid-template-rows: subgrid) {
  @media screen and (min-width: 561px) {
    .grid { align-items: stretch; }
    .card:not(.has-table) { display: grid; grid-template-rows: subgrid; row-gap: 0; align-content: start; grid-row: span 6; }
    .card-compact:not(.has-table) { grid-row: span 4; }
    .card:not(.has-table) > .grade-badge { justify-self: start; align-self: start; }
    .card:not(.has-table) > .formula-math { align-self: center; width: 100%; }
    .card:not(.has-table) > .legend { align-self: start; }
  }
}
.card:target { border-color: var(--algebra-color); box-shadow: 0 0 0 3px rgba(37,99,235,.18); }
.card.has-table { grid-column: 1 / -1; }
.formula-title { font-size: 1.1rem; line-height: 1.3; margin-bottom: 6px; padding-right: 34px; }
.grade-badge { display: inline-block; font-size: .75rem; background: #E2E8F0; padding: 2px 9px; border-radius: 12px; color: var(--text-soft); }
.fav-btn {
  position: absolute; top: 14px; right: 14px; width: 32px; height: 32px; padding: 0;
  background: none; border: 0; font-size: 1.4rem; line-height: 1; color: #94A3B8; cursor: pointer;
  transition: color .2s, transform .1s;
}
.fav-btn:hover { transform: scale(1.15); }
.fav-btn.active { color: #F59E0B; }

.formula-math { margin: 12px 0 4px; max-width: 100%; overflow-x: auto; overflow-y: hidden; text-align: center; }
.formula-math .katex { font-size: 1.3em; }
.formula-math .katex-display { margin: .2em 0; }
.formula-desc { font-size: .92rem; color: var(--text-soft); margin: 8px 0 0; }

.more-toggle {
  display: inline-flex; align-items: center; gap: 6px; margin-top: 12px; padding: 7px 12px;
  background: none; border: 1px solid var(--border-color); border-radius: 8px;
  font-size: .85rem; font-weight: 600; color: var(--algebra-color); cursor: pointer; text-align: left;
}
.more-toggle:hover { border-color: var(--algebra-color); }
.more-toggle .chev { flex-shrink: 0; transition: transform .2s; }
.more-toggle[aria-expanded="true"] .chev { transform: rotate(180deg); }
.js .card-more { display: none; }
.js .card.open .card-more { display: block; }

.formula-diagram { margin: 12px 0 0; padding: 12px; background: #fff; border: 1px solid var(--border-color); border-radius: 8px; text-align: center; }
.formula-diagram svg { display: block; width: 100%; max-width: 240px; height: auto; margin: 0 auto; }
.diagram-caption { font-size: .8rem; color: var(--text-muted); margin-top: 8px; }

.formula-legend {
  margin-top: 12px; padding: 10px 14px; background: #F1F5F9; border-left: 3px solid var(--algebra-color);
  border-radius: 6px; font-size: .85rem; color: var(--text-soft);
}
.legend-title { display: block; margin-bottom: 6px; color: var(--text-main); }
.formula-legend ul { list-style: none; display: flex; flex-wrap: wrap; gap: 4px 16px; }
.formula-legend li { overflow-wrap: anywhere; }

.calculator-box { margin-top: 14px; padding: 14px; background: #F8FAFC; border: 1px solid var(--border-color); border-radius: 8px; }
.calc-row { margin-bottom: 8px; }
.calc-row label { display: block; font-size: .85rem; color: var(--text-soft); }
.calc-input { width: 100%; margin-top: 4px; padding: 8px 12px; font-size: 16px; border: 1px solid #CBD5E1; border-radius: 6px; background: #fff; }
.result-box { margin-top: 10px; padding: 8px 10px; background: #E0F2FE; color: #0369A1; border-radius: 6px; font-size: .9rem; font-weight: 700; overflow-wrap: anywhere; }

.value-table-wrap { margin-top: 12px; overflow-x: auto; border: 1px solid var(--border-color); border-radius: 8px; }
.value-table { width: 100%; border-collapse: collapse; font-size: .9rem; white-space: nowrap; }
.value-table th, .value-table td { padding: 8px 10px; text-align: center; border-bottom: 1px solid var(--border-color); border-right: 1px solid var(--border-color); }
.value-table th:last-child, .value-table td:last-child { border-right: 0; }
.value-table thead th { background: #F1F5F9; font-weight: 700; }
.value-table tbody th { background: #F8FAFC; font-style: italic; }
.value-table tbody tr:last-child th, .value-table tbody tr:last-child td { border-bottom: 0; }

.card-compact { padding: 14px; }
.card-compact .formula-title { font-size: .98rem; }
.card-compact .formula-math .katex { font-size: 1.15em; }
.legend-inline { margin-top: 8px; padding: 8px 10px; font-size: .78rem; }

.empty-note { text-align: center; color: var(--text-muted); padding: 40px 16px; }

/* --- головна: картки тем --- */
.home-section { margin-top: 32px; }
.home-section h2 { font-size: 1.25rem; margin-bottom: 14px; }
.topic-grid { display: grid; gap: 16px; grid-template-columns: repeat(auto-fill, minmax(min(100%, 260px), 1fr)); }
.topic-card {
  display: block; min-width: 0; padding: 18px; background: #fff; border: 1px solid var(--border-color);
  border-radius: var(--border-radius); color: inherit; text-decoration: none; box-shadow: 0 1px 3px rgba(0,0,0,.04);
  transition: border-color .2s, box-shadow .2s, transform .1s;
}
.topic-card:hover { border-color: var(--algebra-color); box-shadow: 0 6px 16px rgba(15,23,42,.08); transform: translateY(-1px); }
.topic-card-subject { display: inline-block; padding: 2px 9px; border-radius: 12px; font-size: .72rem; font-weight: 700; background: var(--algebra-bg); color: #1D4ED8; }
.topic-card[data-subject="geometry"] .topic-card-subject { background: var(--geometry-bg); color: #047857; }
.topic-card-title { font-size: 1.08rem; margin: 8px 0 2px; }
.topic-card-meta { font-size: .82rem; font-weight: 600; color: var(--text-muted); margin-bottom: 8px; }
.topic-card-blurb { font-size: .88rem; color: var(--text-soft); }
.prose p { max-width: 75ch; color: var(--text-soft); line-height: 1.7; }

.sheet-section { margin-bottom: 28px; }
.sheet-heading { font-size: 1.15rem; margin-bottom: 12px; break-after: avoid; }
.sheet-heading a { color: inherit; text-decoration: none; }
.sheet-heading a:hover { color: var(--algebra-color); }

.related { margin-top: 36px; }
.related h2 { font-size: 1.15rem; margin-bottom: 12px; }
.related-list { list-style: none; display: flex; flex-wrap: wrap; gap: 10px; }
.related-list a {
  display: inline-block; padding: 8px 14px; background: #fff; border: 1px solid var(--border-color);
  border-radius: 999px; color: var(--text-main); text-decoration: none; font-size: .9rem;
}
.related-list a:hover { border-color: var(--algebra-color); color: var(--algebra-color); }

/* --- підвал --- */
.site-footer { margin-top: 40px; padding: 40px 32px 24px; background: #fff; border-top: 1px solid var(--border-color); }
.footer-inner { max-width: 1100px; margin: 0 auto; display: grid; gap: 32px; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); }
.footer-col h2 { font-size: .95rem; font-weight: 700; margin-bottom: 10px; }
.footer-col p { font-size: .85rem; line-height: 1.6; color: var(--text-muted); }
.footer-col a { text-decoration: none; }
.footer-col a:hover { text-decoration: underline; }
.footer-copy { max-width: 1100px; margin: 32px auto 0; padding-top: 16px; border-top: 1px solid var(--border-color); font-size: .78rem; color: var(--text-muted); text-align: center; }

/* ===================== адаптивність ===================== */
@media (max-width: 1024px) {
  .app-container { padding: 20px; gap: 20px; }
  .sidebar { flex-basis: 210px; width: 210px; }
}

@media (max-width: 860px) {
  .header { padding: 10px 16px; }
  .sidebar-toggle { display: flex; }
  .app-container { display: block; padding: 16px; }
  .sidebar {
    position: fixed; top: 0; left: 0; z-index: 50; width: 82%; max-width: 320px; height: 100%; max-height: none;
    border-radius: 0; overflow-y: auto; box-shadow: 4px 0 24px rgba(0,0,0,.15);
    visibility: hidden; transform: translateX(-100%); transition: transform .25s ease, visibility 0s linear .25s;
  }
  .sidebar.open { visibility: visible; transform: none; transition: transform .25s ease; }
  .hero h1 { font-size: 1.65rem; }
  .site-footer { padding: 32px 16px 20px; }
}

@media (max-width: 560px) {
  .logo { font-size: 1.3rem; }
  .header-actions { gap: 8px; }
  .header-actions .btn { padding: 10px 12px; }
  .header-actions .btn span {
    position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap;
  }
  .lang-switch a { padding: 6px 9px; }
  .hero h1 { font-size: 1.4rem; }
  .hero p { font-size: .95rem; }
  .grid, .grid-compact, .topic-grid { grid-template-columns: minmax(0, 1fr); gap: 14px; }
  .card { padding: 16px; }
  .card-compact { padding: 12px; }
  .toolbar .btn, .filters .btn { width: 100%; }
  .view-btn, .subject-btn { padding: 7px 12px; font-size: .82rem; }
  .class-chip { padding: 5px 12px; font-size: .82rem; }
  .toc ol { columns: 1; }
}

@media (max-width: 360px) {
  .class-chip { padding: 5px 10px; font-size: .76rem; }
  .lang-switch a { padding: 6px 7px; font-size: .8rem; }
}

/* ===================== друк (шпаргалка) ===================== */
@page { size: A4; margin: 12mm; }

@media print {
  .skip-link, .lang-suggest, .header, .sidebar, .sidebar-overlay, .search-row, .toolbar, .filters, .toc,
  .breadcrumbs, .related, .site-footer, .fav-btn, .more-toggle, .calculator-box, .print-tip, .empty-note,
  .topic-intro, .topic-meta, .home-section { display: none !important; }

  body { background: #fff !important; color: #000 !important; font-size: 10pt; }
  .app-container { display: block; max-width: none; padding: 0; }
  .main-content { display: block; width: 100%; }
  .hero { margin: 0 0 8px; text-align: left; }
  .hero h1 { font-size: 15pt; }

  .card-more { display: block !important; }
  .grid, .grid-compact { display: grid; align-items: start; gap: 8px; grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .card { padding: 6px 8px; border: 1px solid #000; border-radius: 4px; box-shadow: none; break-inside: avoid; }
  .card.has-table { grid-column: 1 / -1; }
  .formula-title { font-size: 10pt; padding-right: 0; }
  .formula-desc { font-size: 8pt; margin-top: 4px; }
  .formula-math { margin: 6px 0 2px; overflow: hidden; }
  .formula-math .katex, .card-compact .formula-math .katex { font-size: 14px; }
  .formula-legend { margin-top: 6px; padding: 4px 6px; font-size: 7.5pt; background: #fff; border-left: 2px solid #000; }
  .formula-legend ul { gap: 2px 8px; }
  .formula-diagram { margin-top: 4px; padding: 4px 0; border: 0; }
  .formula-diagram svg { max-width: 140px; }
  .diagram-caption { display: none; }
  body[data-kind="sheet"] .formula-diagram, body[data-kind="sheet"] .formula-desc { display: none !important; }
  .sheet-section { margin-bottom: 10px; }
  .sheet-heading { font-size: 11pt; margin-bottom: 6px; }
  .value-table-wrap { overflow: visible; border-radius: 4px; }
  .value-table { font-size: 8pt; white-space: normal; table-layout: fixed; }
  .value-table th, .value-table td { padding: 3px 2px; }
}