/* =============================================
   THEME SYSTEM
   ============================================= */
:root {
  --font-display: 'Instrument Sans', sans-serif;
  --font-body: 'Libre Franklin', sans-serif;
  --font-mono: 'JetBrains Mono', monospace;
  --radius-xs: 6px;
  --radius-sm: 10px;
  --radius-md: 14px;
  --radius-lg: 20px;
  --transition-fast: 0.12s ease;
  --transition-base: 0.22s ease;
  --transition-smooth: 0.35s cubic-bezier(0.16, 1, 0.3, 1);
}

[data-theme="light"] {
  --bg-base: #F6F5F1;
  --bg-card: #FFFFFF;
  --bg-card-alt: #FAFAF8;
  --bg-input: #FFFFFF;
  --bg-input-focus: #FFFFFF;
  --bg-hover: #F0EFEB;
  --bg-active: #E8F5F1;
  --bg-pill: #EFEEEA;
  --bg-pill-active: #1B1B1B;
  --bg-swap: #F0EFEB;
  --border-main: #E0DED8;
  --border-light: #EAE8E3;
  --border-focus: #2DBE9E;
  --text-primary: #1A1A1A;
  --text-secondary: #6B6B6B;
  --text-tertiary: #9C9C9C;
  --text-pill-active: #FFFFFF;
  --text-on-accent: #FFFFFF;
  --accent: #2DBE9E;
  --accent-hover: #26A88B;
  --accent-soft: rgba(45, 190, 158, 0.08);
  --accent-glow: rgba(45, 190, 158, 0.15);
  --result-text: #1A1A1A;
  --formula-bg: #F6F5F1;
  --formula-text: #6B6B6B;
  --shadow-card: 0 1px 3px rgba(0,0,0,0.04), 0 6px 24px rgba(0,0,0,0.03);
  --shadow-input: 0 1px 2px rgba(0,0,0,0.04);
  --shadow-input-focus: 0 0 0 3px rgba(45, 190, 158, 0.12);
  --shadow-pill: none;
  --scrollbar-track: transparent;
  --scrollbar-thumb: #D5D3CD;
  --divider: #EAE8E3;
}

[data-theme="dark"] {
  --bg-base: #0C0D0F;
  --bg-card: #151618;
  --bg-card-alt: #1A1B1E;
  --bg-input: #1E1F23;
  --bg-input-focus: #22242A;
  --bg-hover: #1E1F23;
  --bg-active: #142B25;
  --bg-pill: #1E1F23;
  --bg-pill-active: #E8E8E8;
  --bg-swap: #1E1F23;
  --border-main: #2A2B30;
  --border-light: #222328;
  --border-focus: #2DBE9E;
  --text-primary: #EAEAEA;
  --text-secondary: #8A8A8A;
  --text-tertiary: #555555;
  --text-pill-active: #111111;
  --text-on-accent: #FFFFFF;
  --accent: #2DBE9E;
  --accent-hover: #3DD4B2;
  --accent-soft: rgba(45, 190, 158, 0.08);
  --accent-glow: rgba(45, 190, 158, 0.12);
  --result-text: #EAEAEA;
  --formula-bg: #1A1B1E;
  --formula-text: #777;
  --shadow-card: 0 1px 3px rgba(0,0,0,0.2), 0 8px 30px rgba(0,0,0,0.15);
  --shadow-input: 0 1px 2px rgba(0,0,0,0.2);
  --shadow-input-focus: 0 0 0 3px rgba(45, 190, 158, 0.15);
  --shadow-pill: none;
  --scrollbar-track: transparent;
  --scrollbar-thumb: #333;
  --divider: #222328;
}

/* =============================================
   RESET
   ============================================= */
*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }
html { font-size: 16px; -webkit-font-smoothing: antialiased; -moz-osx-font-smoothing: grayscale; }
body {
  font-family: var(--font-body);
  background: var(--bg-base);
  color: var(--text-primary);
  min-height: 100vh;
  transition: background var(--transition-base), color var(--transition-base);
  line-height: 1.55;
}
::-webkit-scrollbar { width: 5px; height: 5px; }
::-webkit-scrollbar-track { background: var(--scrollbar-track); }
::-webkit-scrollbar-thumb { background: var(--scrollbar-thumb); border-radius: 3px; }
button { font-family: inherit; cursor: pointer; border: none; background: none; }
select { font-family: inherit; }
input { font-family: inherit; }

/* =============================================
   LAYOUT
   ============================================= */
.app { max-width: 1200px; margin: 0 auto; padding: 1.75rem 1.25rem 3.5rem; }

/* =============================================
   HEADER
   ============================================= */
.site-header {
  background: var(--bg-card);
  border-bottom: 1px solid var(--border-main);
  padding: 0 24px;
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}
.header-inner {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}
.brand { display: flex; align-items: center; gap: 0.75rem; text-decoration: none; color: var(--text-primary); }
.brand-mark {
  width: 36px; height: 36px;
  background: linear-gradient(135deg, var(--accent), #1A9080);
  border-radius: var(--radius-xs);
  display: flex; align-items: center; justify-content: center;
  box-shadow: 0 2px 10px var(--accent-glow);
  flex-shrink: 0;
}
.brand-mark svg { width: 18px; height: 18px; color: #fff; }
.brand-info h1 {
  font-family: var(--font-display);
  font-size: 20px;
  font-weight: 700;
  letter-spacing: -0.025em;
  line-height: 1.15;
}
.logo-sub {
  display: block;
  font-size: 11px;
  color: var(--text-tertiary);
  font-weight: 400;
  letter-spacing: 0.01em;
  margin-top: 1px;
}
.header-actions {
  display: flex;
  align-items: center;
  gap: 8px;
}
.privacy-badge {
  display: flex; align-items: center; gap: 6px; padding: 6px 12px;
  background: rgba(52, 211, 153, 0.1); color: #34d399; border-radius: 100px;
  font-size: 12px; font-weight: 500; letter-spacing: 0.01em;
}
.privacy-dot {
  width: 6px; height: 6px; border-radius: 50%; background: #34d399;
  animation: pulse-privacy 2s ease infinite;
}
@keyframes pulse-privacy { 0%, 100% { opacity: 1; } 50% { opacity: 0.4; } }
.theme-btn {
  width: 40px; height: 40px;
  border-radius: var(--radius-xs);
  border: 1px solid var(--border-main);
  background: var(--bg-card);
  color: var(--text-secondary);
  cursor: pointer;
  display: flex; align-items: center; justify-content: center;
  transition: all var(--transition-fast);
}
.theme-btn:hover { border-color: var(--accent); color: var(--accent); background: var(--accent-soft); }
.theme-btn svg { width: 17px; height: 17px; }
[data-theme="light"] .moon-icon { display: none; }
[data-theme="dark"] .sun-icon { display: none; }

/* =============================================
   CATEGORY PILLS
   ============================================= */
.categories-wrap {
  margin-bottom: 1.25rem;
  position: relative;
}
.categories-track {
  display: flex;
  gap: 6px;
  overflow-x: auto;
  scroll-behavior: smooth;
  padding: 4px 0;
  -ms-overflow-style: none;
  scrollbar-width: none;
}
.categories-track::-webkit-scrollbar { display: none; }
.cat-pill {
  flex-shrink: 0;
  padding: 0.4rem 0.85rem;
  border-radius: 100px;
  font-family: var(--font-display);
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--text-secondary);
  background: var(--bg-pill);
  border: 1px solid transparent;
  transition: all var(--transition-fast);
  white-space: nowrap;
  display: flex; align-items: center; gap: 0.4rem;
  letter-spacing: -0.01em;
}
.cat-pill:hover { color: var(--text-primary); background: var(--bg-hover); }
.cat-pill.active {
  background: var(--bg-pill-active);
  color: var(--text-pill-active);
  box-shadow: var(--shadow-pill);
}
.cat-pill .cat-emoji { font-size: 0.85rem; line-height: 1; }

/* =============================================
   CONVERTER CARD
   ============================================= */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border-main);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-card);
  transition: background var(--transition-base), border-color var(--transition-base);
  overflow: hidden;
}

/* — Converter body — */
.converter-body { padding: 1.5rem; }

.unit-row {
  display: flex;
  align-items: stretch;
  gap: 0.75rem;
  margin-bottom: 0.75rem;
}
.unit-row:last-child { margin-bottom: 0; }

.unit-select-wrap {
  width: 48%;
  min-width: 0;
}
.unit-select-wrap label {
  display: block;
  font-size: 0.68rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-tertiary);
  margin-bottom: 0.35rem;
  padding-left: 2px;
}
.unit-select {
  width: 100%;
  padding: 0.6rem 2rem 0.6rem 0.75rem;
  border: 1px solid var(--border-main);
  border-radius: var(--radius-sm);
  background: var(--bg-input);
  color: var(--text-primary);
  font-size: 0.85rem;
  font-weight: 500;
  appearance: none;
  cursor: pointer;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' fill='none' stroke='%23888' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M3 4.5 6 7.5 9 4.5'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 0.65rem center;
}
.unit-select:focus { outline: none; border-color: var(--border-focus); box-shadow: var(--shadow-input-focus); }

.value-input-wrap {
  flex: 1;
  min-width: 0;
}
.value-input-wrap label {
  display: block;
  font-size: 0.68rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-tertiary);
  margin-bottom: 0.35rem;
  padding-left: 2px;
}
.value-input {
  width: 100%;
  padding: 0.6rem 0.75rem;
  border: 1px solid var(--border-main);
  border-radius: var(--radius-sm);
  background: var(--bg-input);
  color: var(--text-primary);
  font-family: var(--font-mono);
  font-size: 1rem;
  font-weight: 500;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
  box-shadow: var(--shadow-input);
}
.value-input:focus { outline: none; border-color: var(--border-focus); box-shadow: var(--shadow-input-focus); background: var(--bg-input-focus); }
.value-input::placeholder { color: var(--text-tertiary); font-weight: 400; }

/* — Swap button row — */
.swap-row {
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 0.35rem 0;
}
.swap-btn {
  width: 36px; height: 36px;
  border-radius: 50%;
  background: var(--bg-swap);
  border: 1px solid var(--border-main);
  color: var(--text-secondary);
  display: flex; align-items: center; justify-content: center;
  transition: all var(--transition-fast);
}
.swap-btn:hover {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--accent-soft);
  transform: rotate(180deg);
}
.swap-btn svg { width: 16px; height: 16px; }

/* — Result display — */
.result-area {
  margin-top: 1rem;
  padding: 1rem 1.15rem;
  background: var(--bg-card-alt);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-md);
  min-height: 56px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
}
.result-text {
  font-family: var(--font-mono);
  font-size: 1.4rem;
  font-weight: 500;
  color: var(--result-text);
  line-height: 1.3;
  word-break: break-all;
}
.result-text .result-unit {
  font-size: 0.82rem;
  color: var(--text-secondary);
  font-weight: 400;
  margin-left: 0.35rem;
}
.result-placeholder {
  color: var(--text-tertiary);
  font-size: 0.88rem;
  font-weight: 400;
  font-family: var(--font-body);
}
.copy-btn {
  flex-shrink: 0;
  width: 34px; height: 34px;
  border-radius: var(--radius-xs);
  background: var(--bg-pill);
  color: var(--text-secondary);
  display: flex; align-items: center; justify-content: center;
  transition: all var(--transition-fast);
  border: 1px solid var(--border-light);
  opacity: 0;
  pointer-events: none;
}
.copy-btn.visible { opacity: 1; pointer-events: auto; }
.copy-btn:hover { color: var(--accent); border-color: var(--accent); background: var(--accent-soft); }
.copy-btn svg { width: 15px; height: 15px; }

/* — Formula bar — */
.formula-bar {
  margin-top: 0.65rem;
  padding: 0.6rem 0.85rem;
  background: var(--formula-bg);
  border-radius: var(--radius-xs);
  font-family: var(--font-mono);
  font-size: 0.72rem;
  color: var(--formula-text);
  line-height: 1.5;
  display: none;
}
.formula-bar.visible { display: block; }

/* =============================================
   QUICK REFERENCE TABLE
   ============================================= */
.ref-section {
  border-top: 1px solid var(--divider);
  padding: 1.15rem 1.5rem;
}
.ref-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  cursor: pointer;
  user-select: none;
}
.ref-header h3 {
  font-family: var(--font-display);
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--text-secondary);
  letter-spacing: -0.01em;
}
.ref-chevron {
  width: 16px; height: 16px;
  color: var(--text-tertiary);
  transition: transform var(--transition-base);
}
.ref-section.open .ref-chevron { transform: rotate(180deg); }
.ref-table-wrap {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.35s ease;
}
.ref-section.open .ref-table-wrap { max-height: 500px; }
.ref-table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 0.75rem;
  font-size: 0.78rem;
}
.ref-table th {
  text-align: left;
  font-weight: 600;
  color: var(--text-tertiary);
  font-size: 0.68rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  padding: 0.4rem 0.5rem;
  border-bottom: 1px solid var(--divider);
}
.ref-table td {
  padding: 0.4rem 0.5rem;
  color: var(--text-secondary);
  border-bottom: 1px solid var(--divider);
  font-family: var(--font-mono);
  font-size: 0.75rem;
}
.ref-table tr:last-child td { border-bottom: none; }
.ref-table .ref-val { color: var(--text-primary); font-weight: 500; }

/* =============================================
   FOOTER
   ============================================= */
.footer {
  text-align: center;
  margin-top: 2rem;
  font-size: 0.74rem;
  color: var(--text-tertiary);
}

/* =============================================
   ANIMATIONS
   ============================================= */
@keyframes fadeUp {
  from { opacity: 0; transform: translateY(14px); }
  to { opacity: 1; transform: translateY(0); }
}
.card { animation: fadeUp 0.45s cubic-bezier(0.16, 1, 0.3, 1) both; animation-delay: 0.08s; }
.categories-wrap { animation: fadeUp 0.4s cubic-bezier(0.16, 1, 0.3, 1) both; }

/* =============================================
   RESPONSIVE
   ============================================= */
@media (max-width: 600px) {
  .app { padding: 1.25rem 0.85rem 3rem; }
  .header-inner { height: 56px; }
  .brand-info h1 { font-size: 17px; }
  .logo-sub { display: none; }
  .privacy-badge span:not(.privacy-dot) { display: none; }
  .privacy-badge { padding: 8px; }
  .converter-body { padding: 1.15rem; }
  .unit-row { flex-direction: column; gap: 0.6rem; }
  .unit-select-wrap { width: 100%; }
  .result-text { font-size: 1.15rem; }
  .ref-section { padding: 1rem 1.15rem; }
}

/* ===== SITE FOOTER ===== */
.site-footer{
  margin-top:60px;padding:48px 28px 36px;
  border-top:1px solid var(--border-main);
  background:var(--bg-base);color:var(--text-secondary);
  font-family:-apple-system,BlinkMacSystemFont,'Segoe UI',Roboto,sans-serif;
  font-size:14px;line-height:1.6;
}
.site-footer .footer-inner{max-width:1100px;margin:0 auto}
.site-footer .footer-grid{
  display:grid;grid-template-columns:2fr 1fr 1fr 1fr;
  gap:40px;margin-bottom:40px;
}
.site-footer .footer-brand{display:flex;align-items:center;gap:10px;margin-bottom:16px}
.site-footer .footer-brand svg{width:32px;height:32px;color:#a855f7;flex-shrink:0}
.site-footer .footer-brand-name{
  font-size:20px;font-weight:700;
  background:linear-gradient(90deg,#8B5CF6,#EC4899,#3B82F6);
  -webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text;
}
.site-footer .footer-desc{color:var(--text-tertiary);margin-bottom:16px;max-width:360px}
.site-footer .footer-copy{font-size:12px;color:var(--text-tertiary);opacity:.7}
.site-footer h4{font-weight:700;margin-bottom:16px;color:var(--text-primary);font-size:15px}
.site-footer ul{list-style:none;padding:0;margin:0;display:flex;flex-direction:column;gap:10px}
.site-footer a{color:var(--text-secondary);text-decoration:none;transition:color .2s}
.site-footer a:hover{color:#a855f7}
.site-footer .footer-bottom{
  border-top:1px solid var(--border-main);
  padding-top:20px;text-align:center;
}
.site-footer .footer-bottom p{color:var(--text-tertiary);font-size:13px;opacity:.7}
.site-footer .footer-bottom span{color:#a855f7}

@media(max-width:768px){
  .site-footer .footer-grid{grid-template-columns:1fr;gap:32px}
  .site-footer{padding:36px 16px 28px}
}