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

:root {
  --header-h: 52px;
  --tabs-h: 42px;
  --sidebar-w: 320px;
  --color-bg: #f5f6f8;
  --color-surface: #ffffff;
  --color-primary: #1a56db;
  --color-primary-light: #e8eefb;
  --color-text: #1f2937;
  --color-text-secondary: #6b7280;
  --color-border: #e5e7eb;
  --color-hover: #f3f4f6;
  --color-accent-it: #16a34a;
  --color-accent-eu: #2563eb;
  --color-accent-ec: #9333ea;
  --color-accent-pdf: #dc2626;
  --radius: 6px;
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.06);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.1);
  --transition: 0.2s ease;
}

html, body {
  height: 100%;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  font-size: 14px;
  color: var(--color-text);
  background: var(--color-bg);
  overflow: hidden;
}

/* ===== Header ===== */
.header {
  height: var(--header-h);
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 16px;
  gap: 16px;
  z-index: 100;
  position: relative;
}

.header-left {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-shrink: 0;
}

.header-title {
  font-size: 16px;
  font-weight: 700;
  color: var(--color-text);
  white-space: nowrap;
}

.home-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  border: none;
  background: none;
  color: var(--color-text-secondary);
  cursor: pointer;
  border-radius: var(--radius);
  transition: background var(--transition), color var(--transition);
}
.home-btn:hover {
  background: var(--color-primary-light);
  color: var(--color-primary);
}

.sidebar-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  border: none;
  background: none;
  color: var(--color-text-secondary);
  cursor: pointer;
  border-radius: var(--radius);
  transition: background var(--transition);
}
.sidebar-toggle:hover {
  background: var(--color-hover);
  color: var(--color-text);
}

.header-right {
  flex: 1;
  max-width: 480px;
}

.search-box {
  position: relative;
  display: flex;
  align-items: center;
}
.search-icon {
  position: absolute;
  left: 10px;
  color: var(--color-text-secondary);
  pointer-events: none;
}
.search-box input {
  width: 100%;
  height: 34px;
  padding: 0 70px 0 34px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  font-size: 13px;
  background: var(--color-bg);
  color: var(--color-text);
  outline: none;
  transition: border-color var(--transition), box-shadow var(--transition);
}
.search-box input:focus {
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(26, 86, 219, 0.1);
}
.search-box input::placeholder {
  color: var(--color-text-secondary);
}
.search-shortcut {
  position: absolute;
  right: 8px;
  font-size: 11px;
  padding: 2px 6px;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 4px;
  color: var(--color-text-secondary);
  font-family: inherit;
  pointer-events: none;
}

/* ===== Tabs ===== */
.tabs {
  height: var(--tabs-h);
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  display: flex;
  align-items: stretch;
  padding: 0 16px;
  gap: 2px;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}
.tabs::-webkit-scrollbar { height: 0; }

.tab {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 0 14px;
  border: none;
  background: none;
  font-size: 13px;
  font-weight: 500;
  color: var(--color-text-secondary);
  cursor: pointer;
  white-space: nowrap;
  border-bottom: 2px solid transparent;
  transition: color var(--transition), border-color var(--transition);
}
.tab:hover {
  color: var(--color-text);
  background: var(--color-hover);
}
.tab.active {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
}

.tab-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 22px;
  height: 18px;
  border-radius: 3px;
  font-size: 10px;
  font-weight: 700;
  color: #fff;
  background: var(--color-accent-eu);
}
.tab[data-standard="ntc2018"] .tab-icon { background: var(--color-accent-it); }
.tab[data-standard="sren1997"] .tab-icon { background: var(--color-accent-eu); }
.tab[data-standard="quickec7"] .tab-icon { background: var(--color-accent-ec); }
.tab-pdf .tab-icon { background: var(--color-accent-pdf); }
.tab-ec .tab-icon { background: #0369a1; font-size: 8px; width: 26px; }
.tab-cr .tab-icon { background: #b45309; }

.tab-separator {
  width: 1px;
  margin: 8px 4px;
  background: var(--color-border);
  flex-shrink: 0;
}

/* ===== Main Layout ===== */
.main {
  display: flex;
  height: calc(100vh - var(--header-h) - var(--tabs-h));
}

/* ===== Sidebar ===== */
.sidebar {
  width: var(--sidebar-w);
  min-width: var(--sidebar-w);
  background: var(--color-surface);
  border-right: 1px solid var(--color-border);
  display: flex;
  flex-direction: column;
  transition: margin-left var(--transition), opacity var(--transition);
  overflow: hidden;
}
.sidebar.collapsed {
  margin-left: calc(var(--sidebar-w) * -1);
  opacity: 0;
}

.sidebar-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 14px;
  border-bottom: 1px solid var(--color-border);
  flex-shrink: 0;
}
.sidebar-title {
  font-size: 13px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--color-text-secondary);
}

.collapse-all-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 26px;
  height: 26px;
  border: none;
  background: none;
  color: var(--color-text-secondary);
  cursor: pointer;
  border-radius: var(--radius);
  transition: background var(--transition), transform var(--transition);
}
.collapse-all-btn:hover {
  background: var(--color-hover);
}
.collapse-all-btn.collapsed {
  transform: rotate(-90deg);
}

.toc-container {
  flex: 1;
  overflow-y: auto;
  padding: 6px 0;
}
.toc-container::-webkit-scrollbar { width: 5px; }
.toc-container::-webkit-scrollbar-thumb { background: #ccc; border-radius: 3px; }

.toc-loading {
  padding: 20px;
  text-align: center;
  color: var(--color-text-secondary);
  font-size: 13px;
}

/* TOC Tree */
.toc-tree {
  list-style: none;
  padding: 0;
  margin: 0;
}
.toc-tree ul {
  list-style: none;
  padding-left: 16px;
  margin: 0;
}
.toc-tree li {
  margin: 0;
}

.toc-item {
  display: flex;
  align-items: center;
  gap: 4px;
  padding: 5px 10px 5px 8px;
  cursor: pointer;
  border-radius: 4px;
  margin: 1px 6px;
  font-size: 13px;
  line-height: 1.4;
  color: var(--color-text);
  text-decoration: none;
  transition: background var(--transition);
  word-break: break-word;
}
.toc-item:hover {
  background: var(--color-hover);
}
.toc-item.active {
  background: var(--color-primary-light);
  color: var(--color-primary);
  font-weight: 500;
}

.toc-toggle {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 18px;
  height: 18px;
  flex-shrink: 0;
  color: var(--color-text-secondary);
  transition: transform var(--transition);
}
.toc-toggle.expanded {
  transform: rotate(90deg);
}
.toc-toggle svg {
  width: 10px;
  height: 10px;
}

.toc-leaf-spacer {
  width: 18px;
  flex-shrink: 0;
}

.toc-tree li > ul {
  display: none;
}
.toc-tree li.expanded > ul {
  display: block;
}

/* Search highlight in TOC */
.toc-item mark {
  background: #fef08a;
  color: inherit;
  padding: 0 1px;
  border-radius: 2px;
}
.toc-item.search-hidden {
  display: none;
}
li.search-hidden {
  display: none;
}

/* ===== Content Area ===== */
.content {
  flex: 1;
  overflow: hidden;
  background: var(--color-bg);
  position: relative;
  min-width: 0;
}

.content-frame {
  width: 100%;
  height: 100%;
  border: none;
  background: #fff;
}

.pdf-viewer {
  width: 100%;
  height: 100%;
}
.pdf-frame {
  width: 100%;
  height: 100%;
  border: none;
}

/* ===== Welcome Screen ===== */
.welcome {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 40px 20px;
  text-align: center;
  color: var(--color-text-secondary);
  overflow-y: auto;
  height: 100%;
}
.welcome-icon {
  color: var(--color-border);
  margin-bottom: 16px;
}
.welcome h2 {
  font-size: 22px;
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: 8px;
}
.welcome p {
  font-size: 14px;
  max-width: 400px;
  margin-bottom: 32px;
}

.welcome-cards {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
  justify-content: center;
}
.welcome-card {
  width: 200px;
  padding: 20px 16px;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 8px;
  cursor: pointer;
  transition: border-color var(--transition), box-shadow var(--transition), transform var(--transition);
  text-align: left;
}
.welcome-card:hover {
  border-color: var(--color-primary);
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}
.card-badge {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 28px;
  height: 22px;
  border-radius: 4px;
  font-size: 11px;
  font-weight: 700;
  color: #fff;
  margin-bottom: 10px;
}
.welcome-card[data-standard="ntc2018"] .card-badge { background: var(--color-accent-it); }
.welcome-card[data-standard="sren1997"] .card-badge { background: var(--color-accent-eu); }
.welcome-card[data-standard="quickec7"] .card-badge { background: var(--color-accent-ec); }

.welcome-card h3 {
  font-size: 14px;
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: 4px;
}
.welcome-card p {
  font-size: 12px;
  margin-bottom: 0;
  color: var(--color-text-secondary);
}

.card-quicklink {
  display: inline-block;
  margin-top: 10px;
  padding: 5px 10px;
  font-size: 11px;
  font-weight: 600;
  color: var(--color-accent-it);
  background: #f0fdf4;
  border: 1px solid #bbf7d0;
  border-radius: 4px;
  text-decoration: none;
  transition: background var(--transition), color var(--transition);
}
.card-quicklink:hover {
  background: #dcfce7;
  color: #15803d;
}
.card-quicklink.ec {
  background: #f0f9ff;
  border-color: #bae6fd;
  color: #0369a1;
}
.card-quicklink.ec:hover {
  background: #e0f2fe;
  color: #075985;
}

.welcome-card-wide {
  width: 100%;
  max-width: 440px;
}
.card-ec-links {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin-top: 10px;
}
.ec-badge {
  background: #0369a1 !important;
}
.cr-badge {
  background: #b45309 !important;
}
.welcome-card[data-standard="eurocode"] {
  cursor: default;
}
.welcome-card[data-standard="eurocode"]:hover {
  transform: none;
}

/* ===== Quick Tables Section ===== */
.quick-tables {
  width: 100%;
  max-width: 900px;
  margin-top: 36px;
  text-align: left;
}
.quick-tables-title {
  font-size: 15px;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: 16px;
  padding-bottom: 8px;
  border-bottom: 2px solid var(--color-accent-it);
  display: inline-block;
}

.quick-tables-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 16px;
}

.quick-table-group {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 8px;
  padding: 14px;
}
.quick-table-group h4 {
  font-size: 12px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.4px;
  color: var(--color-text-secondary);
  margin-bottom: 8px;
  padding-bottom: 6px;
  border-bottom: 1px solid var(--color-border);
}

.quick-table-link {
  display: flex;
  align-items: baseline;
  gap: 8px;
  padding: 6px 8px;
  margin: 2px -4px;
  border-radius: 4px;
  font-size: 12.5px;
  color: var(--color-text);
  text-decoration: none;
  cursor: pointer;
  transition: background var(--transition);
  line-height: 1.4;
}
.quick-table-link:hover {
  background: var(--color-primary-light);
  color: var(--color-primary);
}

.qt-tag {
  display: inline-block;
  flex-shrink: 0;
  padding: 1px 6px;
  font-size: 10px;
  font-weight: 700;
  border-radius: 3px;
  background: #e8eefb;
  color: var(--color-primary);
  white-space: nowrap;
}
.qt-tag.pdf {
  background: #fef2f2;
  color: var(--color-accent-pdf);
}

@media (max-width: 768px) {
  .quick-tables-grid {
    grid-template-columns: 1fr;
  }
}

/* ===== Search Overlay ===== */
.search-overlay {
  display: none;
  position: fixed;
  top: var(--header-h);
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0,0,0,0.3);
  z-index: 90;
}
.search-overlay.visible {
  display: block;
}

.search-results {
  position: absolute;
  top: 0;
  right: 0;
  width: 480px;
  max-width: 100%;
  max-height: calc(100vh - var(--header-h));
  background: var(--color-surface);
  border-left: 1px solid var(--color-border);
  box-shadow: var(--shadow-md);
  overflow-y: auto;
  padding: 12px;
}
.search-results::-webkit-scrollbar { width: 5px; }
.search-results::-webkit-scrollbar-thumb { background: #ccc; border-radius: 3px; }

.search-result-item {
  padding: 10px 12px;
  border-radius: var(--radius);
  cursor: pointer;
  transition: background var(--transition);
}
.search-result-item:hover {
  background: var(--color-hover);
}
.search-result-item .result-standard {
  font-size: 10px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--color-primary);
  margin-bottom: 2px;
}
.search-result-item .result-title {
  font-size: 13px;
  font-weight: 500;
  color: var(--color-text);
}
.search-result-item .result-title mark {
  background: #fef08a;
  color: inherit;
  padding: 0 1px;
  border-radius: 2px;
}
.search-result-item .result-path {
  font-size: 11px;
  color: var(--color-text-secondary);
  margin-top: 2px;
}

.search-no-results {
  padding: 20px;
  text-align: center;
  color: var(--color-text-secondary);
  font-size: 13px;
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
  :root {
    --sidebar-w: 280px;
  }

  .header-title { display: none; }
  .search-shortcut { display: none; }

  .sidebar {
    position: fixed;
    top: calc(var(--header-h) + var(--tabs-h));
    left: 0;
    bottom: 0;
    z-index: 80;
    box-shadow: var(--shadow-md);
  }
  .sidebar.collapsed {
    margin-left: calc(var(--sidebar-w) * -1);
  }

  .search-results {
    width: 100%;
  }

  .welcome-cards {
    flex-direction: column;
    align-items: center;
  }
}