/* Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 200;
  background: var(--bg-primary);
  border-bottom: 1px solid var(--border);
  height: var(--header-height);
  box-shadow: var(--shadow-sm);
}

.header-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
  height: 100%;
  display: flex;
  align-items: center;
  gap: 24px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--primary);
  flex-shrink: 0;
}

.logo-icon {
  width: 36px;
  height: 36px;
  background: var(--primary);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  font-size: 1.1rem;
}

.logo-text { color: var(--text-primary); }
.logo-text span { color: var(--primary); }

.header-nav {
  display: flex;
  align-items: center;
  gap: 4px;
}

.nav-link {
  padding: 8px 14px;
  border-radius: var(--radius-md);
  font-size: 0.9375rem;
  font-weight: 500;
  color: var(--text-secondary);
  transition: all var(--transition);
}

.nav-link:hover,
.nav-link.active {
  color: var(--primary);
  background: var(--primary-light);
}

.header-search {
  flex: 1;
  max-width: 400px;
  position: relative;
}

.search-input-wrap {
  display: flex;
  align-items: center;
  gap: 8px;
  background: var(--bg-secondary);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-full);
  padding: 8px 16px;
  transition: all var(--transition);
}

.search-input-wrap:focus-within {
  border-color: var(--primary);
  background: var(--bg-primary);
  box-shadow: 0 0 0 3px rgb(37 99 235 / 0.12);
}

.search-icon {
  color: var(--gray-400);
  flex-shrink: 0;
  width: 18px;
  height: 18px;
}

.search-input {
  border: none;
  background: transparent;
  outline: none;
  width: 100%;
  font-size: 0.9375rem;
  color: var(--text-primary);
}

.search-input::placeholder {
  color: var(--gray-400);
}

.search-results-dropdown {
  position: absolute;
  top: calc(100% + 8px);
  left: 0;
  right: 0;
  background: var(--bg-primary);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg);
  max-height: 380px;
  overflow-y: auto;
  z-index: 300;
  display: none;
}

.search-results-dropdown.open {
  display: block;
}

.search-result-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px 16px;
  cursor: pointer;
  transition: background var(--transition);
  border-bottom: 1px solid var(--border);
}

.search-result-item:last-child { border-bottom: none; }

.search-result-item:hover,
.search-result-item.focused {
  background: var(--bg-secondary);
}

.search-result-name {
  font-weight: 600;
  font-size: 0.9375rem;
}

.search-result-desc {
  font-size: 0.8125rem;
  color: var(--text-secondary);
  margin-top: 2px;
}

.search-no-results {
  padding: 24px;
  text-align: center;
  color: var(--text-secondary);
  font-size: 0.9375rem;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-shrink: 0;
}

.theme-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 38px;
  height: 38px;
  border-radius: var(--radius-md);
  color: var(--text-secondary);
  transition: all var(--transition);
  cursor: pointer;
}

.theme-toggle:hover {
  background: var(--bg-secondary);
  color: var(--text-primary);
}

/* Hamburger */
.hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  width: 38px;
  height: 38px;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  border-radius: var(--radius-md);
  transition: background var(--transition);
}

.hamburger:hover { background: var(--bg-secondary); }

.hamburger span {
  display: block;
  width: 20px;
  height: 2px;
  background: var(--text-primary);
  border-radius: 2px;
  transition: all 0.3s ease;
}

/* Mobile nav */
.mobile-nav {
  display: none;
  flex-direction: column;
  position: fixed;
  top: var(--header-height);
  left: 0;
  right: 0;
  bottom: 0;
  background: var(--bg-primary);
  padding: 24px;
  gap: 8px;
  z-index: 150;
  overflow-y: auto;
  border-top: 1px solid var(--border);
}

.mobile-nav.open {
  display: flex;
}

.mobile-nav .nav-link {
  font-size: 1.0625rem;
  padding: 12px 16px;
}

/* Main container */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

/* Page wrapper */
.page-wrap {
  min-height: calc(100vh - var(--header-height));
}

/* Footer */
.site-footer {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border);
  padding: 48px 0 32px;
  margin-top: 80px;
}

.footer-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 48px;
  margin-bottom: 48px;
}

.footer-brand .logo {
  margin-bottom: 16px;
}

.footer-tagline {
  font-size: 0.9375rem;
  color: var(--text-secondary);
  line-height: 1.6;
  max-width: 280px;
}

.footer-col-title {
  font-weight: 700;
  font-size: 0.9375rem;
  margin-bottom: 16px;
  color: var(--text-primary);
}

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

.footer-links a {
  font-size: 0.9375rem;
  color: var(--text-secondary);
  transition: color var(--transition);
}

.footer-links a:hover { color: var(--primary); }

.footer-bottom {
  padding-top: 32px;
  border-top: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 16px;
  font-size: 0.875rem;
  color: var(--text-secondary);
}

.footer-bottom-links {
  display: flex;
  gap: 24px;
}

.footer-bottom-links a:hover { color: var(--primary); }

/* Calculator Page Layout */
.calc-page {
  padding: 24px 0 48px;
}

.calc-breadcrumb {
  margin-bottom: 24px;
}

.calc-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 32px;
  align-items: start;
}

.calc-panel {
  background: var(--bg-primary);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 28px;
  box-shadow: var(--shadow-sm);
}

.calc-panel-title {
  font-size: 1.125rem;
  font-weight: 700;
  margin-bottom: 20px;
  padding-bottom: 16px;
  border-bottom: 1px solid var(--border);
  color: var(--text-primary);
}

.calc-inputs {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.calc-actions {
  display: flex;
  gap: 12px;
  margin-top: 24px;
  padding-top: 20px;
  border-top: 1px solid var(--border);
}

.calc-results {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.calc-result-hidden {
  text-align: center;
  padding: 40px 20px;
  color: var(--text-secondary);
}

.calc-result-hidden svg {
  margin: 0 auto 16px;
  opacity: 0.4;
}

/* Category page */
.cat-hero {
  padding: 40px 0;
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border);
  margin-bottom: 40px;
}

.cat-hero-inner {
  display: flex;
  align-items: center;
  gap: 24px;
}

.cat-icon-large {
  width: 64px;
  height: 64px;
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  font-size: 2rem;
}

.cat-hero-title {
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 8px;
}

.cat-hero-desc {
  font-size: 1rem;
  color: var(--text-secondary);
}

.cat-hero-count {
  font-size: 0.875rem;
  color: var(--text-secondary);
  margin-top: 8px;
}

/* Grid layouts */
.grid-2 { display: grid; grid-template-columns: repeat(2, 1fr); gap: 24px; }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }
.grid-4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: 24px; }
.grid-auto { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 24px; }

/* Hero */
.hero {
  padding: 64px 0 48px;
  background: linear-gradient(135deg, var(--primary-light) 0%, var(--bg-primary) 100%);
  border-bottom: 1px solid var(--border);
}

.hero-title {
  font-size: 3rem;
  font-weight: 800;
  line-height: 1.2;
  color: var(--text-primary);
  margin-bottom: 16px;
}

.hero-title span { color: var(--primary); }

.hero-subtitle {
  font-size: 1.125rem;
  color: var(--text-secondary);
  margin-bottom: 32px;
  max-width: 560px;
}

.hero-search {
  max-width: 600px;
  margin-bottom: 24px;
}

.hero-search .search-input-wrap {
  padding: 14px 20px;
  border-radius: var(--radius-lg);
  font-size: 1rem;
}

.hero-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 32px;
}

.hero-stats {
  display: flex;
  align-items: center;
  gap: 32px;
  flex-wrap: wrap;
}

.hero-stat {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.9375rem;
  color: var(--text-secondary);
}

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

/* Sections */
.section {
  padding: 64px 0;
}

.section + .section {
  padding-top: 0;
}

/* Category cards (homepage) */
.cat-card {
  display: flex;
  flex-direction: column;
  gap: 16px;
  padding: 24px;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border);
  background: var(--bg-primary);
  cursor: pointer;
  transition: all var(--transition);
  text-decoration: none;
  color: inherit;
}

.cat-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
}

.cat-card-icon {
  width: 52px;
  height: 52px;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
}

.cat-card-name {
  font-size: 1.0625rem;
  font-weight: 700;
}

.cat-card-desc {
  font-size: 0.875rem;
  color: var(--text-secondary);
  line-height: 1.5;
}

.cat-card-count {
  font-size: 0.8125rem;
  color: var(--text-secondary);
  margin-top: auto;
}

/* Features section */
.feature-card {
  display: flex;
  flex-direction: column;
  gap: 12px;
  padding: 24px;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border);
  background: var(--bg-primary);
}

.feature-icon {
  width: 48px;
  height: 48px;
  border-radius: var(--radius-md);
  background: var(--primary-light);
  color: var(--primary);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.25rem;
}

.feature-title {
  font-size: 1rem;
  font-weight: 700;
}

.feature-desc {
  font-size: 0.875rem;
  color: var(--text-secondary);
  line-height: 1.5;
}

/* Explanation section */
.explanation-section {
  padding: 48px 0;
  border-top: 1px solid var(--border);
  margin-top: 48px;
}

.explanation-section h2 {
  font-size: 1.5rem;
  margin-bottom: 16px;
}

.explanation-section h3 {
  font-size: 1.125rem;
  margin: 24px 0 12px;
}

.explanation-section p {
  color: var(--text-secondary);
  line-height: 1.7;
  margin-bottom: 12px;
}

.formula-box {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 16px 20px;
  font-family: var(--font-mono);
  font-size: 0.9rem;
  color: var(--text-primary);
  overflow-x: auto;
  margin: 16px 0;
}

/* FAQ */
.faq-item {
  border-bottom: 1px solid var(--border);
}

.faq-question {
  width: 100%;
  text-align: left;
  padding: 16px 0;
  font-weight: 600;
  font-size: 0.9375rem;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  cursor: pointer;
  background: transparent;
  border: none;
  transition: color var(--transition);
}

.faq-question:hover { color: var(--primary); }

.faq-chevron {
  flex-shrink: 0;
  transition: transform 0.3s ease;
}

.faq-item.open .faq-chevron {
  transform: rotate(180deg);
}

.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.35s ease, padding 0.2s ease;
}

.faq-item.open .faq-answer {
  max-height: 400px;
  padding-bottom: 16px;
}

.faq-answer p {
  color: var(--text-secondary);
  font-size: 0.9375rem;
  line-height: 1.7;
}

/* Related calculators */
.related-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 16px;
}

.related-card {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 14px 16px;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition);
  color: inherit;
  text-decoration: none;
}

.related-card:hover {
  border-color: var(--primary);
  background: var(--primary-light);
}

.related-card-name {
  font-size: 0.9375rem;
  font-weight: 600;
}

.related-card-cat {
  font-size: 0.8125rem;
  color: var(--text-secondary);
}

/* Calc header */
.calc-header {
  margin-bottom: 28px;
}

.calc-title {
  font-size: 1.875rem;
  font-weight: 800;
  margin-bottom: 8px;
}

.calc-desc {
  font-size: 1rem;
  color: var(--text-secondary);
}

/* Action bar on calc pages */
.calc-action-bar {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 16px 24px;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  margin: 32px 0;
  flex-wrap: wrap;
}

.calc-action-bar .btn {
  font-size: 0.875rem;
  padding: 8px 16px;
}

/* Filter bar */
.filter-bar {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
  margin-bottom: 32px;
  padding-bottom: 24px;
  border-bottom: 1px solid var(--border);
}