:root {
  --primary: #1a56db;
  --primary-light: #eff2ff;
  --fg: #111827;
  --fg-muted: #6b7280;
  --bg: #fafafe;
  --card: #ffffff;
  --border: #e5e7f0;
  --radius: 12px;
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

[data-theme="dark"] {
  --primary: #4d7cf4;
  --primary-light: #1a2540;
  --fg: #f3f4f6;
  --fg-muted: #9ca3af;
  --bg: #111827;
  --card: #1f2937;
  --border: #374151;
}

[data-theme="dark"] tr:nth-child(even) td { background: #243044; }

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

body {
  font-family: var(--font);
  font-size: 17px;
  line-height: 1.75;
  color: var(--fg);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
}

a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ── NAV ── */
nav {
  border-bottom: 1px solid var(--border);
  background: var(--card);
  position: sticky;
  top: 0;
  z-index: 10;
}
.nav-inner {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 24px;
  height: 60px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.nav-logo { display: flex; align-items: center; gap: 10px; font-weight: 700; font-size: 18px; color: var(--fg); }
.nav-logo img { height: 32px; }
.nav-links { display: flex; align-items: center; gap: 4px; }
.nav-links a { font-size: 14px; font-weight: 500; color: var(--fg-muted); padding: 6px 10px; border-radius: 6px; }
.nav-links a:hover { color: var(--fg); background: var(--border); text-decoration: none; }
.nav-cta {
  background: var(--primary);
  color: #fff;
  padding: 8px 20px;
  border-radius: 8px;
  font-size: 14px;
  font-weight: 600;
}
.nav-cta:hover { background: #1748c2; text-decoration: none; }
.theme-toggle {
  background: none;
  border: 1px solid var(--border);
  border-radius: 8px;
  width: 36px;
  height: 36px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--fg-muted);
  flex-shrink: 0;
  margin-left: 8px;
}
.theme-toggle:hover { color: var(--fg); border-color: var(--fg-muted); }
.theme-toggle svg { width: 18px; height: 18px; stroke: currentColor; fill: none; stroke-width: 2; stroke-linecap: round; stroke-linejoin: round; }

/* ── BREADCRUMB ── */
.breadcrumb {
  max-width: 760px;
  margin: 24px auto 0;
  padding: 0 24px;
  font-size: 13px;
  color: var(--fg-muted);
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
}
.breadcrumb a { color: var(--fg-muted); }
.breadcrumb a:hover { color: var(--primary); }
.breadcrumb-sep { color: var(--border); }

/* ── ARTICLE ── */
.article {
  max-width: 760px;
  margin: 0 auto;
  padding: 32px 24px 80px;
}

.article-meta {
  display: flex;
  align-items: center;
  gap: 16px;
  margin-bottom: 24px;
  font-size: 13px;
  color: var(--fg-muted);
  flex-wrap: wrap;
}
.article-tag {
  background: var(--primary-light);
  color: var(--primary);
  padding: 3px 10px;
  border-radius: 20px;
  font-size: 12px;
  font-weight: 600;
}

h1 {
  font-size: clamp(28px, 5vw, 40px);
  font-weight: 800;
  line-height: 1.2;
  letter-spacing: -0.02em;
  margin-bottom: 20px;
  color: var(--fg);
}

.article-lead {
  font-size: 18px;
  color: var(--fg-muted);
  line-height: 1.65;
  margin-bottom: 40px;
  border-left: 3px solid var(--primary);
  padding-left: 16px;
}

h2 {
  font-size: 24px;
  font-weight: 700;
  margin-top: 48px;
  margin-bottom: 16px;
  line-height: 1.3;
  color: var(--fg);
}

h3 {
  font-size: 18px;
  font-weight: 600;
  margin-top: 28px;
  margin-bottom: 10px;
  color: var(--fg);
}

p { margin-bottom: 18px; }

ul, ol {
  margin: 0 0 18px 0;
  padding-left: 24px;
}
li { margin-bottom: 8px; }
li:last-child { margin-bottom: 0; }

strong { font-weight: 600; color: var(--fg); }

/* ── CALLOUT ── */
.callout {
  background: var(--primary-light);
  border-left: 4px solid var(--primary);
  border-radius: 0 var(--radius) var(--radius) 0;
  padding: 16px 20px;
  margin: 28px 0;
  font-size: 15px;
}
.callout strong { color: var(--primary); }

/* ── TABLE ── */
table {
  width: 100%;
  border-collapse: collapse;
  margin: 28px 0;
  font-size: 15px;
}
th {
  background: var(--primary-light);
  padding: 10px 14px;
  text-align: left;
  font-weight: 600;
  font-size: 13px;
  color: var(--primary);
  border: 1px solid var(--border);
}
td {
  padding: 10px 14px;
  border: 1px solid var(--border);
  vertical-align: top;
}
tr:nth-child(even) td { background: #f8f9ff; }

/* ── CTA BOX ── */
.cta-box {
  background: linear-gradient(135deg, var(--primary) 0%, #2563eb 100%);
  border-radius: var(--radius);
  padding: 32px;
  margin: 48px 0;
  text-align: center;
  color: #fff;
}
.cta-box h3 {
  font-size: 22px;
  margin-bottom: 10px;
  color: #fff;
  margin-top: 0;
}
.cta-box p { color: rgba(255,255,255,0.85); margin-bottom: 20px; font-size: 15px; }
.cta-btn {
  display: inline-block;
  background: #fff;
  color: var(--primary);
  padding: 12px 28px;
  border-radius: 8px;
  font-weight: 700;
  font-size: 15px;
}
.cta-btn:hover { background: var(--primary-light); text-decoration: none; }

/* ── FAQ ── */
details {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  margin-bottom: 12px;
  overflow: hidden;
}
details[open] { border-color: var(--primary); }
summary {
  padding: 16px 20px;
  cursor: pointer;
  font-weight: 600;
  font-size: 15px;
  list-style: none;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 12px;
}
summary::after { content: "+"; font-size: 20px; color: var(--primary); flex-shrink: 0; }
details[open] summary::after { content: "−"; }
.faq-answer { padding: 0 20px 16px; font-size: 15px; color: var(--fg-muted); }

/* ── BLOG LISTING ── */
.blog-hero {
  max-width: 1100px;
  margin: 0 auto;
  padding: 56px 24px 40px;
  text-align: center;
}
.blog-hero h1 { font-size: clamp(32px, 6vw, 52px); margin-bottom: 16px; }
.blog-hero p { font-size: 18px; color: var(--fg-muted); max-width: 520px; margin: 0 auto; }

.blog-grid {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 24px 80px;
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 24px;
}

.blog-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  transition: box-shadow 0.2s, border-color 0.2s;
}
.blog-card:hover { box-shadow: 0 8px 32px rgba(26,86,219,0.12); border-color: var(--primary); }
.blog-card-body { padding: 24px; }
.blog-card-tag {
  background: var(--primary-light);
  color: var(--primary);
  padding: 3px 10px;
  border-radius: 20px;
  font-size: 12px;
  font-weight: 600;
  display: inline-block;
  margin-bottom: 12px;
}
.blog-card h2 {
  font-size: 19px;
  margin: 0 0 10px;
  line-height: 1.35;
  font-weight: 700;
}
.blog-card p { font-size: 14px; color: var(--fg-muted); margin: 0 0 16px; line-height: 1.6; }
.blog-card-meta { font-size: 12px; color: var(--fg-muted); display: flex; gap: 12px; }
.blog-card-read { color: var(--primary); font-weight: 600; font-size: 14px; display: inline-block; margin-top: 16px; }

/* ── FOOTER ── */
footer, .blog-footer {
  border-top: 1px solid var(--border);
  background: var(--card);
  padding: 24px;
  font-size: 13px;
  color: var(--fg-muted);
}
footer a, .blog-footer a { color: var(--fg-muted); }
footer a:hover, .blog-footer a:hover { color: var(--primary); }
.blog-footer .footer-inner {
  max-width: 1100px;
  margin: 0 auto;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}
.footer-links {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  font-size: 13px;
}
.footer-links a { padding: 2px 4px; }
.footer-sep { color: var(--border); user-select: none; }
.footer-social { display: flex; align-items: center; gap: 6px; }
.footer-social a { display: flex; align-items: center; justify-content: center; width: 28px; height: 28px; border-radius: 6px; color: var(--fg-muted); }
.footer-social a:hover { color: var(--primary); background: var(--border); text-decoration: none; }
.footer-social svg { width: 16px; height: 16px; }

/* ── SCROLL TO TOP ── */
#scrollTopBtn {
  position: fixed;
  bottom: 24px;
  right: 24px;
  z-index: 100;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: var(--card);
  border: 1px solid var(--border);
  color: var(--fg-muted);
  font-size: 22px;
  line-height: 1;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 2px 8px rgba(0,0,0,0.12);
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.2s, color 0.15s, border-color 0.15s;
}
#scrollTopBtn:hover { color: var(--primary); border-color: var(--primary); }

/* ── RESPONSIVE ── */
@media (max-width: 640px) {
  h1 { font-size: 26px; }
  h2 { font-size: 20px; margin-top: 36px; }
  .article { padding: 24px 16px 60px; }
  .cta-box { padding: 24px 20px; }
  .blog-grid { grid-template-columns: 1fr; }
}