*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }

:root {
  --bg: #0a0a0f;
  --surface: rgba(255,255,255,0.03);
  --surface-hover: rgba(255,255,255,0.06);
  --border: rgba(255,255,255,0.08);
  --border-hover: rgba(255,255,255,0.15);
  --text: #e8e8ed;
  --text-dim: rgba(255,255,255,0.4);
  --accent: #6c5ce7;
  --accent-glow: rgba(108,92,231,0.2);
  --green: #00d68f;
  --blue: #5f8ef7;
  --orange: #ff9f43;
  --radius: 12px;
  --radius-sm: 8px;
}

html { font-size: 16px; scroll-behavior: smooth; }
body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
}

/* ─── Header ─── */
.site-header {
  border-bottom: 1px solid var(--border);
  background: rgba(10,10,15,0.8);
  backdrop-filter: blur(12px);
  position: sticky; top: 0; z-index: 100;
}
.nav {
  max-width: 960px; margin: 0 auto; padding: 0.8rem 1.5rem;
  display: flex; align-items: center; justify-content: space-between;
}
.logo { font-size: 1.15rem; font-weight: 700; color: var(--text); text-decoration: none; }
.logo-accent { color: var(--accent); margin-right: 0.25rem; }
.nav-links { display: flex; gap: 1.5rem; }
.nav-links a { color: var(--text-dim); text-decoration: none; font-size: 0.85rem; font-weight: 500; transition: color 0.2s; }
.nav-links a:hover { color: var(--text); }

/* ─── Hero ─── */
.hero { text-align: center; padding: 3rem 1.5rem 1.5rem; }
.hero h1 {
  font-size: clamp(1.8rem, 4vw, 2.8rem); font-weight: 800;
  background: linear-gradient(135deg, #fff, var(--accent));
  -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text;
}
.hero-sub { color: var(--text-dim); margin-top: 0.5rem; font-size: 0.95rem; }

/* ─── Ad Placeholder ─── */
.ad-placeholder {
  max-width: 960px; margin: 1rem auto; padding: 1.5rem;
  border: 1px dashed var(--border); border-radius: var(--radius);
  text-align: center; min-height: 60px;
  display: flex; align-items: center; justify-content: center;
}
.ad-label { font-size: 0.65rem; text-transform: uppercase; letter-spacing: 0.15em; color: var(--text-dim); }

/* ─── Converter ─── */
.converter { max-width: 960px; margin: 0 auto; padding: 0 1.5rem 3rem; }

.category-tabs {
  display: flex; flex-wrap: wrap; gap: 0.4rem;
  margin-bottom: 1.5rem; justify-content: center;
}
.cat-tab {
  padding: 0.45rem 0.9rem; border-radius: 100px; border: 1px solid var(--border);
  background: transparent; color: var(--text-dim); font-size: 0.78rem;
  cursor: pointer; transition: all 0.2s; font-weight: 500;
}
.cat-tab:hover { background: var(--surface-hover); color: var(--text); }
.cat-tab.active { background: var(--accent); border-color: var(--accent); color: #fff; }

.converter-card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 1.5rem;
  transition: border-color 0.2s;
}
.converter-card:focus-within { border-color: var(--accent); }

.input-row {
  display: grid; grid-template-columns: 1fr auto 1fr;
  gap: 0.75rem; align-items: end;
}
.input-group { display: flex; flex-direction: column; gap: 0.35rem; }
.input-group label { font-size: 0.7rem; text-transform: uppercase; letter-spacing: 0.08em; color: var(--text-dim); font-weight: 600; }
.input-group input {
  width: 100%; padding: 0.75rem 1rem; border-radius: var(--radius-sm);
  border: 1px solid var(--border); background: rgba(0,0,0,0.3);
  color: var(--text); font-size: 1.3rem; font-weight: 600; font-family: 'JetBrains Mono', monospace;
  outline: none; transition: border 0.2s;
}
.input-group input:focus { border-color: var(--accent); }
.input-group select {
  width: 100%; padding: 0.55rem 0.75rem; border-radius: var(--radius-sm);
  border: 1px solid var(--border); background: rgba(0,0,0,0.3);
  color: var(--text); font-size: 0.85rem; cursor: pointer; outline: none;
}
.swap-btn {
  padding: 0.5rem; border-radius: 50%; border: 1px solid var(--border);
  background: transparent; color: var(--text-dim); font-size: 1.3rem;
  cursor: pointer; transition: all 0.2s; line-height: 1; margin-bottom: 0;
}
.swap-btn:hover { background: var(--surface-hover); color: var(--accent); border-color: var(--accent); }

.result-row {
  margin-top: 1rem; padding: 1rem; border-radius: var(--radius-sm);
  background: rgba(108,92,231,0.08); border: 1px solid rgba(108,92,231,0.2);
  display: none; align-items: center; gap: 0.75rem;
}
.result-row.show { display: flex; }
.result-text { flex: 1; font-size: 1rem; line-height: 1.5; }
.result-highlight {
  font-size: 1.2rem; font-weight: 700; font-family: 'JetBrains Mono', monospace;
  background: linear-gradient(135deg, var(--accent), var(--blue));
  -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text;
}
.copy-btn {
  padding: 0.4rem 0.7rem; border-radius: var(--radius-sm); border: 1px solid var(--border);
  background: transparent; color: var(--text-dim); font-size: 1rem;
  cursor: pointer; transition: all 0.2s; font-size: 0.9rem;
}
.copy-btn:hover { background: var(--surface-hover); color: var(--text); }

.formula-box { margin-top: 0.5rem; text-align: center; }
.formula { font-size: 0.8rem; color: var(--text-dim); font-family: 'JetBrains Mono', monospace; }

/* ─── Quick Table ─── */
.quick-table { margin-top: 2rem; }
.quick-table h3 { font-size: 0.9rem; font-weight: 600; margin-bottom: 0.75rem; color: var(--text-dim); }
.table-wrap { overflow-x: auto; }
.quick-table table { width: 100%; border-collapse: collapse; font-size: 0.85rem; }
.quick-table th { text-align: left; padding: 0.5rem 0.75rem; border-bottom: 1px solid var(--border); color: var(--text-dim); font-weight: 600; }
.quick-table td { padding: 0.4rem 0.75rem; border-bottom: 1px solid var(--border); }
.quick-table tr:last-child td { border-bottom: none; }
.quick-table tr:hover td { background: var(--surface-hover); }

/* ─── SEO Content ─── */
.seo-content { margin-top: 3rem; padding-top: 2rem; border-top: 1px solid var(--border); }
.seo-content h2 { font-size: 1.2rem; font-weight: 700; margin-bottom: 0.75rem; }
.seo-content p { color: var(--text-dim); line-height: 1.7; font-size: 0.9rem; margin-bottom: 0.75rem; }

/* ─── Page Content (About, Privacy, Contact) ─── */
.page-content { max-width: 760px; margin: 0 auto; padding: 3rem 1.5rem; }
.page-content h1 { font-size: 1.8rem; font-weight: 800; margin-bottom: 0.5rem; }
.page-content .page-updated { color: var(--text-dim); font-size: 0.85rem; margin-bottom: 2rem; }
.page-content h2 { font-size: 1.15rem; font-weight: 700; margin: 1.5rem 0 0.75rem; }
.page-content p, .page-content li { color: var(--text-dim); line-height: 1.7; font-size: 0.9rem; margin-bottom: 0.5rem; }
.page-content ul { padding-left: 1.25rem; }
.page-content a { color: var(--accent); text-decoration: none; }
.page-content a:hover { text-decoration: underline; }

/* ─── Footer ─── */
.site-footer {
  border-top: 1px solid var(--border); padding: 2rem 1.5rem;
  text-align: center;
}
.footer-content { max-width: 960px; margin: 0 auto; }
.footer-links { display: flex; justify-content: center; gap: 1.5rem; margin-bottom: 0.75rem; }
.footer-links a { color: var(--text-dim); text-decoration: none; font-size: 0.8rem; transition: color 0.2s; }
.footer-links a:hover { color: var(--text); }
.footer-copy { font-size: 0.75rem; color: var(--text-dim); }

/* ─── Responsive ─── */
@media (max-width: 600px) {
  .input-row { grid-template-columns: 1fr; }
  .swap-btn { justify-self: center; padding: 0.4rem; }
  .nav { padding: 0.6rem 1rem; }
  .hero { padding: 2rem 1rem 1rem; }
  .converter { padding: 0 1rem 2rem; }
  .converter-card { padding: 1rem; }
}