/* ============================================
   Multi-Unit Converter - Shared Stylesheet
   Modern design v2.0
   ============================================ */

/* ---------- Design Tokens ---------- */
:root {
  --primary: #3B82F6;
  --primary-dark: #2563EB;
  --primary-light: #60A5FA;
  --navy: #0F172A;
  --navy-2: #1E293B;
  --purple: #764BA2;
  --sky: #0EA5E9;
  --bg: #F8FAFC;
  --bg-alt: #F1F5F9;
  --white: #FFFFFF;
  --text: #334155;
  --text-gray: #64748B;
  --text-light: #94A3B8;
  --border: #E2E8F0;
  --border-hover: #CBD5E1;
  --success: #10B981;
  --error: #EF4444;
  --warning: #F59E0B;
  --shadow-xs: 0 1px 2px rgba(15, 23, 42, 0.04);
  --shadow-sm: 0 2px 8px rgba(15, 23, 42, 0.06);
  --shadow-md: 0 8px 24px rgba(15, 23, 42, 0.08);
  --shadow-lg: 0 20px 40px rgba(15, 23, 42, 0.12);
  --shadow-glow: 0 0 0 4px rgba(59, 130, 246, 0.12);
  --radius: 16px;
  --radius-sm: 10px;
  --radius-xs: 6px;
  --transition: 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 0.35s cubic-bezier(0.4, 0, 0.2, 1);
  --gradient-primary: linear-gradient(135deg, #3B82F6 0%, #764BA2 100%);
  --gradient-subtle: linear-gradient(135deg, #EFF6FF 0%, #F5F3FF 100%);
}

/* ---------- Reset ---------- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  font-size: 16px;
  line-height: 1.6;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}
a { color: var(--primary); text-decoration: none; transition: color var(--transition); }
a:hover { color: var(--primary-dark); }
img { max-width: 100%; height: auto; }

/* ---------- Sticky Header ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border);
}
.header-inner {
  max-width: 1200px;
  margin: 0 auto;
  padding: 14px 24px;
  display: flex;
  align-items: center;
  gap: 24px;
}
.site-logo {
  color: var(--navy);
  font-size: 20px;
  font-weight: 700;
  white-space: nowrap;
  display: flex;
  align-items: center;
  gap: 10px;
  letter-spacing: -0.02em;
}
.site-logo i { color: var(--primary); font-size: 22px; }
.site-logo:hover { color: var(--navy); }
.header-search {
  flex: 1;
  max-width: 420px;
  position: relative;
}
.header-search input {
  width: 100%;
  padding: 11px 16px 11px 40px;
  border: 1.5px solid var(--border);
  border-radius: 100px;
  background: var(--white);
  font-size: 14px;
  font-family: inherit;
  outline: none;
  transition: all var(--transition);
  color: var(--navy);
}
.header-search input:focus { border-color: var(--primary); box-shadow: var(--shadow-glow); }
.header-search i {
  position: absolute;
  left: 16px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--text-light);
  font-size: 14px;
  pointer-events: none;
}
.search-results {
  position: absolute;
  top: calc(100% + 8px);
  left: 0;
  right: 0;
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  box-shadow: var(--shadow-lg);
  max-height: 340px;
  overflow-y: auto;
  display: none;
}
.search-results.show { display: block; }
.search-results a {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 11px 16px;
  color: var(--navy);
  border-bottom: 1px solid var(--bg-alt);
  font-size: 14px;
  transition: background var(--transition);
}
.search-results a i { color: var(--text-light); font-size: 12px; }
.search-results a:hover { background: var(--bg-alt); color: var(--primary); }
.search-results a:hover i { color: var(--primary); }
.search-results a:last-child { border-bottom: none; }

/* ---------- Breadcrumb ---------- */
.breadcrumb {
  max-width: 1200px;
  margin: 0 auto;
  padding: 20px 24px 0;
  font-size: 13px;
  color: var(--text-gray);
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
}
.breadcrumb a { color: var(--text-gray); display: inline-flex; align-items: center; gap: 6px; }
.breadcrumb a:hover { color: var(--primary); }
.breadcrumb i { font-size: 10px; color: var(--text-light); }

/* ---------- Page Container ---------- */
.page-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 24px;
  display: grid;
  grid-template-columns: 1fr 300px;
  gap: 32px;
}
.main-column { min-width: 0; }
.sidebar { min-width: 0; }

/* ---------- Page Heading ---------- */
.page-heading { margin-bottom: 24px; }
.page-heading .eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 6px 14px;
  background: var(--gradient-subtle);
  border: 1px solid var(--border);
  border-radius: 100px;
  font-size: 12px;
  font-weight: 600;
  color: var(--primary);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 16px;
}
.page-heading h1 {
  font-size: 40px;
  font-weight: 800;
  color: var(--navy);
  letter-spacing: -0.03em;
  line-height: 1.1;
  margin-bottom: 12px;
}
.page-heading h1 .accent {
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}
.page-heading .subtitle {
  color: var(--text-gray);
  font-size: 17px;
  max-width: 680px;
  line-height: 1.55;
}

/* ---------- Converter Widget ---------- */
.converter-card {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 32px;
  box-shadow: var(--shadow-sm);
  margin-bottom: 28px;
  position: relative;
  overflow: hidden;
}
.converter-card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: var(--gradient-primary);
}

.converter-row {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  gap: 16px;
  align-items: end;
  margin-bottom: 20px;
}
.field-group { display: flex; flex-direction: column; gap: 8px; }
.field-group label {
  font-size: 12px;
  font-weight: 600;
  color: var(--text-gray);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  display: flex;
  align-items: center;
  gap: 6px;
}
.converter-input, .converter-select {
  width: 100%;
  padding: 14px 16px;
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 16px;
  font-family: inherit;
  color: var(--navy);
  background: var(--white);
  transition: all var(--transition);
  outline: none;
  font-weight: 500;
}
.converter-input:hover, .converter-select:hover { border-color: var(--border-hover); }
.converter-input:focus, .converter-select:focus {
  border-color: var(--primary);
  box-shadow: var(--shadow-glow);
}
.converter-select {
  cursor: pointer;
  appearance: none;
  background-image: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' width='12' height='8' viewBox='0 0 12 8'><path d='M1 1l5 5 5-5' stroke='%2364748B' stroke-width='2' fill='none' stroke-linecap='round' stroke-linejoin='round'/></svg>");
  background-repeat: no-repeat;
  background-position: right 16px center;
  padding-right: 40px;
}

.swap-btn {
  width: 48px;
  height: 48px;
  margin-bottom: 2px;
  border: 1.5px solid var(--border);
  border-radius: 50%;
  background: var(--white);
  color: var(--primary);
  font-size: 16px;
  cursor: pointer;
  transition: all var(--transition-slow);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}
.swap-btn:hover {
  border-color: var(--primary);
  background: var(--primary);
  color: var(--white);
  transform: rotate(180deg);
  box-shadow: var(--shadow-md);
}

/* ---------- Result Section ---------- */
.result-box {
  background: var(--gradient-subtle);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 24px 28px;
  margin-bottom: 20px;
  position: relative;
  min-height: 90px;
}
.result-label {
  font-size: 11px;
  font-weight: 700;
  color: var(--text-gray);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  margin-bottom: 8px;
  display: flex;
  align-items: center;
  gap: 6px;
}
.result-main {
  font-size: 26px;
  font-weight: 700;
  color: var(--navy);
  word-break: break-word;
  line-height: 1.3;
  letter-spacing: -0.02em;
}
.result-sub {
  font-size: 14px;
  color: var(--text-gray);
  margin-top: 6px;
}
.copy-btn {
  position: absolute;
  top: 16px;
  right: 16px;
  padding: 8px 14px;
  border: 1px solid var(--border);
  border-radius: 100px;
  background: var(--white);
  color: var(--text);
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition);
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-family: inherit;
}
.copy-btn:hover { background: var(--navy); color: var(--white); border-color: var(--navy); }
.copy-btn i { font-size: 11px; }

/* ---------- Action Buttons ---------- */
.action-row {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}
.btn {
  padding: 11px 20px;
  border: 1.5px solid transparent;
  border-radius: var(--radius-sm);
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition);
  font-family: inherit;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  white-space: nowrap;
}
.btn i { font-size: 13px; }
.btn-primary { background: var(--primary); color: var(--white); border-color: var(--primary); }
.btn-primary:hover { background: var(--primary-dark); border-color: var(--primary-dark); transform: translateY(-1px); box-shadow: var(--shadow-md); }
.btn-secondary { background: var(--white); color: var(--text); border-color: var(--border); }
.btn-secondary:hover { border-color: var(--border-hover); background: var(--bg-alt); }
.btn-ghost { background: transparent; color: var(--primary); border-color: var(--primary); }
.btn-ghost:hover { background: var(--primary); color: var(--white); }

/* ---------- Formula Box ---------- */
.formula-box {
  margin-top: 16px;
  padding: 18px 20px;
  background: #FFFBEB;
  border: 1px solid #FDE68A;
  border-left: 3px solid var(--warning);
  border-radius: var(--radius-sm);
  font-family: 'SF Mono', 'Fira Code', Monaco, Consolas, monospace;
  font-size: 14px;
  color: #78350F;
  display: none;
  animation: slideDown 0.25s ease;
}
.formula-box.show { display: block; }
.formula-box strong {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 8px;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  color: #92400E;
  font-size: 13px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}
@keyframes slideDown { from { opacity: 0; transform: translateY(-8px); } to { opacity: 1; transform: translateY(0); } }

/* ---------- Quick Reference Grid ---------- */
.section-title {
  font-size: 22px;
  font-weight: 700;
  color: var(--navy);
  margin: 40px 0 20px;
  display: flex;
  align-items: center;
  gap: 10px;
  letter-spacing: -0.02em;
}
.section-title i { color: var(--primary); font-size: 18px; }
.quick-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 12px;
}
.quick-card {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 16px 18px;
  cursor: pointer;
  transition: all var(--transition);
  text-align: left;
  font-family: inherit;
  color: inherit;
  position: relative;
  overflow: hidden;
}
.quick-card::after {
  content: "";
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  height: 2px;
  background: var(--gradient-primary);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform var(--transition);
}
.quick-card:hover {
  border-color: var(--primary);
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}
.quick-card:hover::after { transform: scaleX(1); }
.quick-card .value {
  font-size: 18px;
  font-weight: 700;
  color: var(--navy);
  word-break: break-word;
  letter-spacing: -0.01em;
}
.quick-card .unit {
  font-size: 12px;
  color: var(--text-gray);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-top: 4px;
  font-weight: 500;
}

/* ---------- SEO Content Sections ---------- */
.content-section { margin-top: 44px; }
.content-section h2 {
  font-size: 24px;
  font-weight: 700;
  color: var(--navy);
  margin-bottom: 14px;
  letter-spacing: -0.02em;
  display: flex;
  align-items: center;
  gap: 10px;
}
.content-section h2 i { color: var(--primary); font-size: 18px; }
.content-section p { margin-bottom: 14px; color: var(--text); font-size: 16px; line-height: 1.7; }
.content-section .formula-inline {
  display: inline-block;
  padding: 3px 10px;
  background: var(--bg-alt);
  border: 1px solid var(--border);
  border-radius: var(--radius-xs);
  font-family: 'SF Mono', Monaco, Consolas, monospace;
  font-size: 14px;
  color: var(--navy);
  font-weight: 500;
}
.content-section strong { color: var(--navy); font-weight: 600; }

/* ---------- Conversion Table ---------- */
.conv-table {
  width: 100%;
  border-collapse: collapse;
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  overflow: hidden;
  margin: 16px 0;
  box-shadow: var(--shadow-xs);
}
.conv-table th {
  background: var(--bg-alt);
  color: var(--navy);
  padding: 14px 18px;
  text-align: left;
  font-size: 13px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  border-bottom: 1px solid var(--border);
}
.conv-table td {
  padding: 12px 18px;
  border-bottom: 1px solid var(--bg-alt);
  font-size: 15px;
  color: var(--text);
}
.conv-table tr:last-child td { border-bottom: none; }
.conv-table tr:hover td { background: #F8FAFC; }
.conv-table td:last-child { font-weight: 600; color: var(--navy); font-variant-numeric: tabular-nums; }

/* ---------- Popular Conversions Grid ---------- */
.popular-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 10px;
  margin-top: 16px;
}
.popular-link {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px 16px;
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--navy);
  font-size: 14px;
  font-weight: 500;
  transition: all var(--transition);
}
.popular-link i { color: var(--text-light); font-size: 11px; transition: transform var(--transition), color var(--transition); }
.popular-link:hover {
  border-color: var(--primary);
  color: var(--primary);
  transform: translateY(-1px);
  box-shadow: var(--shadow-sm);
}
.popular-link:hover i { transform: translateX(4px); color: var(--primary); }

/* ---------- Sidebar ---------- */
.sidebar-card {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow-xs);
  margin-bottom: 20px;
}
.sidebar-card h3 {
  font-size: 12px;
  font-weight: 700;
  color: var(--text-gray);
  margin-bottom: 14px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  display: flex;
  align-items: center;
  gap: 8px;
}
.sidebar-card h3 i { color: var(--primary); font-size: 11px; }
.sidebar-card ul { list-style: none; }
.sidebar-card li { margin-bottom: 2px; }
.sidebar-card a {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 12px;
  border-radius: var(--radius-xs);
  color: var(--text);
  font-size: 14px;
  font-weight: 500;
  transition: all var(--transition);
}
.sidebar-card a i { color: var(--text-light); width: 16px; font-size: 13px; text-align: center; }
.sidebar-card a:hover { background: var(--bg-alt); color: var(--navy); }
.sidebar-card a:hover i { color: var(--primary); }
.sidebar-card a.active {
  background: var(--gradient-subtle);
  color: var(--primary);
  font-weight: 600;
}
.sidebar-card a.active i { color: var(--primary); }
.shortcut-list { font-size: 13px; color: var(--text-gray); }
.shortcut-list li { padding: 8px 0; display: flex; justify-content: space-between; align-items: center; border-bottom: 1px solid var(--bg-alt); }
.shortcut-list li:last-child { border-bottom: none; }
.shortcut-list kbd {
  background: var(--bg-alt);
  border: 1px solid var(--border);
  border-bottom-width: 2px;
  border-radius: 4px;
  padding: 2px 7px;
  font-size: 11px;
  font-family: 'SF Mono', Monaco, monospace;
  color: var(--navy);
  font-weight: 600;
}

/* ---------- Toast Notification ---------- */
.toast {
  position: fixed;
  top: 24px;
  right: 24px;
  padding: 14px 20px;
  border-radius: var(--radius-sm);
  color: var(--white);
  font-size: 14px;
  font-weight: 500;
  box-shadow: var(--shadow-lg);
  z-index: 1000;
  opacity: 0;
  transform: translateY(-20px);
  transition: opacity 0.3s, transform 0.3s;
  pointer-events: none;
  display: flex;
  align-items: center;
  gap: 10px;
}
.toast.show { opacity: 1; transform: translateY(0); }
.toast.success { background: var(--success); }
.toast.error { background: var(--error); }
.toast i { font-size: 14px; }

/* ---------- Footer ---------- */
.site-footer {
  background: var(--navy);
  color: #CBD5E1;
  padding: 56px 24px 28px;
  margin-top: 80px;
}
.footer-inner { max-width: 1200px; margin: 0 auto; }
.footer-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 40px;
  margin-bottom: 40px;
}
.footer-grid h4 {
  color: var(--white);
  font-size: 13px;
  margin-bottom: 16px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  display: flex;
  align-items: center;
  gap: 8px;
}
.footer-grid h4 i { color: var(--primary-light); font-size: 12px; }
.footer-grid ul { list-style: none; }
.footer-grid li { margin-bottom: 8px; }
.footer-grid a { color: #94A3B8; font-size: 14px; transition: color var(--transition); }
.footer-grid a:hover { color: var(--white); }
.footer-bottom {
  border-top: 1px solid #1E293B;
  padding-top: 24px;
  text-align: center;
  font-size: 13px;
  color: #64748B;
}

/* ---------- Homepage Hero ---------- */
.hero {
  background: var(--gradient-primary);
  color: var(--white);
  padding: 72px 32px;
  text-align: center;
  border-radius: var(--radius);
  margin-bottom: 40px;
  position: relative;
  overflow: hidden;
}
.hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background: radial-gradient(ellipse at top right, rgba(255,255,255,0.15) 0%, transparent 60%);
}
.hero > * { position: relative; z-index: 1; }
.hero h1 { font-size: 48px; margin-bottom: 16px; font-weight: 800; letter-spacing: -0.03em; line-height: 1.1; color: var(--white); }
.hero p { font-size: 19px; opacity: 0.95; max-width: 640px; margin: 0 auto; line-height: 1.55; }

/* ---------- Category Grid (Homepage) ---------- */
.category-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 20px;
  margin: 32px 0;
}
.category-card {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px 24px;
  box-shadow: var(--shadow-xs);
  transition: all var(--transition);
  display: block;
  color: var(--navy);
  position: relative;
  overflow: hidden;
}
.category-card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: var(--gradient-primary);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform var(--transition);
}
.category-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: transparent;
  color: var(--navy);
}
.category-card:hover::before { transform: scaleX(1); }
.category-card .icon-wrap {
  width: 52px;
  height: 52px;
  border-radius: 14px;
  background: var(--gradient-subtle);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 16px;
  color: var(--primary);
  font-size: 22px;
}
.category-card h3 { font-size: 18px; margin-bottom: 6px; font-weight: 700; letter-spacing: -0.01em; }
.category-card p { font-size: 14px; color: var(--text-gray); line-height: 1.5; }

/* ---------- Responsive (Mobile) ---------- */
@media (max-width: 960px) {
  .page-container { grid-template-columns: 1fr; gap: 24px; }
  .sidebar { order: -1; }
  .sidebar-card { padding: 20px; }
}

@media (max-width: 640px) {
  .header-inner { padding: 12px 16px; gap: 12px; }
  .site-logo { font-size: 17px; }
  .site-logo i { font-size: 19px; }
  .breadcrumb { padding: 14px 16px 0; font-size: 12px; }
  .page-container { padding: 16px; }
  .page-heading h1 { font-size: 30px; }
  .page-heading .subtitle { font-size: 15px; }
  .converter-card { padding: 22px; }
  .converter-row { grid-template-columns: 1fr; gap: 14px; }
  .swap-btn { justify-self: center; transform: rotate(90deg); margin: 4px 0; }
  .swap-btn:hover { transform: rotate(270deg); }
  .result-main { font-size: 21px; }
  .result-box { padding: 20px; }
  .copy-btn { position: static; margin-top: 12px; }
  .quick-grid { grid-template-columns: repeat(auto-fit, minmax(130px, 1fr)); gap: 10px; }
  .quick-card { padding: 12px 14px; }
  .quick-card .value { font-size: 15px; }
  .hero { padding: 48px 24px; }
  .hero h1 { font-size: 32px; }
  .hero p { font-size: 16px; }
  .content-section h2 { font-size: 20px; }
  .section-title { font-size: 19px; }
  .conv-table th, .conv-table td { padding: 10px 12px; font-size: 13px; }
}

/* ---------- Print ---------- */
@media print {
  .site-header, .sidebar, .action-row, .swap-btn, .copy-btn, .site-footer { display: none; }
  body { background: white; }
  .converter-card { box-shadow: none; border: 1px solid #ccc; }
}