:root {
  --bg:#0a0e16; --panel:#0d121c; --panel2:#111826; --line:#1c2636;
  --ink:#eef2f7; --ink-dim:#aeb9c9; --muted:#5f6c80;
  --accent:#5b8def; --danger:#f87171;
  --mono:ui-monospace,'SF Mono','JetBrains Mono',Menlo,Consolas,monospace;
  --sans:-apple-system,BlinkMacSystemFont,'Segoe UI',Inter,sans-serif;
}
[data-theme="light"] {
  --bg:#eef1f5; --panel:#ffffff; --panel2:#f1f4f9; --line:#cdd6e2;
  --ink:#0c121d; --ink-dim:#3a4659; --muted:#7c8aa0; --accent:#2563eb;
}
*, *::before, *::after { box-sizing: border-box; margin: 0; }
html, body { min-height: 100%; }
body {
  background: var(--bg); color: var(--ink);
  font-family: var(--sans); line-height: 1.6;
}
a { color: inherit; text-decoration: none; }

/* ── Top nav ── */
#topnav {
  position: sticky; top: 0; z-index: 10;
  background: var(--panel); border-bottom: 1px solid var(--line);
  display: flex; align-items: center; gap: 0; height: 52px; padding: 0 28px;
}
.nav-logo {
  display: flex; align-items: center; gap: 9px;
  font-weight: 800; font-size: 15px; letter-spacing: -.3px; color: var(--ink);
}
.nav-logo .mark {
  width: 24px; height: 24px; border: 2px solid var(--ink); border-radius: 6px;
  position: relative; flex-shrink: 0;
}
.nav-logo .mark::after {
  content: ''; position: absolute; inset: 5px 5px auto 5px;
  height: 2px; background: var(--ink); box-shadow: 0 5px 0 var(--ink);
}
.nav-sep { width: 1px; height: 20px; background: var(--line); margin: 0 16px; }
.nav-hub { font-size: 13px; color: var(--muted); font-weight: 600; }
.nav-spacer { flex: 1; }
.nav-back {
  font-size: 13px; font-weight: 600; color: var(--muted);
  display: flex; align-items: center; gap: 5px;
  padding: 6px 12px; border-radius: 8px; border: 1px solid var(--line);
  transition: color .12s, border-color .12s;
}
.nav-back:hover { color: var(--ink); border-color: var(--ink-dim); }
.theme-btn {
  background: none; border: 1px solid var(--line); border-radius: 8px;
  width: 34px; height: 34px; cursor: pointer; color: var(--ink);
  display: flex; align-items: center; justify-content: center; margin-left: 10px;
  font-size: 15px;
}

/* ── Page layout ── */
#page { max-width: 800px; margin: 0 auto; padding: 52px 32px 100px; }

/* ── Article header ── */
.art-header { margin-bottom: 42px; }
.art-cat {
  font-family: var(--mono); font-size: 11px; letter-spacing: 2px;
  text-transform: uppercase; margin-bottom: 12px; font-weight: 700;
}
.art-header h1 {
  font-size: 36px; font-weight: 800; letter-spacing: -.9px;
  line-height: 1.18; margin-bottom: 14px; color: var(--ink);
}
.art-desc { font-size: 17px; color: var(--ink-dim); line-height: 1.65; max-width: 620px; }
.art-meta { display: flex; gap: 18px; margin-top: 18px; font-size: 13px; color: var(--muted); }

/* ── Body blocks ── */
.art-h2 {
  font-size: 22px; font-weight: 700; margin: 42px 0 14px;
  letter-spacing: -.3px; color: var(--ink);
}
.art-h3 { font-size: 17px; font-weight: 700; margin: 28px 0 10px; color: var(--ink); }
.art-p  { font-size: 15.5px; line-height: 1.78; color: var(--ink-dim); margin-bottom: 18px; }
.art-p strong { color: var(--ink); font-weight: 600; }
.art-p code {
  background: var(--panel2); border: 1px solid var(--line); border-radius: 4px;
  padding: 1px 6px; font-family: var(--mono); font-size: 13.5px; color: var(--accent);
}
.art-p a { color: var(--accent); text-decoration: underline; text-underline-offset: 3px; }

/* ── Code block ── */
.art-code {
  background: var(--panel2); border: 1px solid var(--line); border-radius: 11px;
  padding: 18px 22px; margin: 20px 0; overflow-x: auto;
}
.art-code .lang {
  font-size: 10px; color: var(--muted); font-family: var(--mono);
  letter-spacing: 1.5px; text-transform: uppercase; margin-bottom: 10px;
}
.art-code pre {
  font-family: var(--mono); font-size: 13.5px; line-height: 1.75;
  color: #a9c7ff; white-space: pre; tab-size: 2;
}

/* ── Callouts ── */
.art-tip, .art-warn, .art-info {
  border-radius: 11px; padding: 15px 20px; margin: 22px 0;
  display: flex; gap: 14px; align-items: flex-start; font-size: 14.5px; line-height: 1.65;
}
.art-tip  { background: rgba(16,185,129,.08);  border: 1px solid rgba(16,185,129,.22); }
.art-warn { background: rgba(245,158,11,.08);  border: 1px solid rgba(245,158,11,.22); }
.art-info { background: rgba(91,141,239,.08);  border: 1px solid rgba(91,141,239,.22); }
.art-callout-icon { font-size: 20px; flex-shrink: 0; line-height: 1.3; }
.art-callout-body { color: var(--ink-dim); }
.art-callout-body strong { color: var(--ink); }

/* ── Steps ── */
.art-steps { display: flex; flex-direction: column; margin: 22px 0; }
.art-step  { display: flex; gap: 18px; padding: 18px 0; border-bottom: 1px solid var(--line); }
.art-step:last-child { border-bottom: none; }
.art-step-num {
  width: 30px; height: 30px; border-radius: 50%; background: var(--accent);
  color: #fff; font-size: 13px; font-weight: 700; flex-shrink: 0; margin-top: 1px;
  display: flex; align-items: center; justify-content: center;
}
.art-step-body h4 { font-size: 15.5px; font-weight: 700; margin-bottom: 6px; color: var(--ink); }
.art-step-body p  { font-size: 14px; color: var(--ink-dim); line-height: 1.65; }
.art-step-body code {
  background: var(--panel2); border: 1px solid var(--line); border-radius: 4px;
  padding: 1px 5px; font-family: var(--mono); font-size: 13px; color: var(--accent);
}

/* ── 2-col feature grid ── */
.art-grid2 { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin: 22px 0; }
.art-grid2 .ag { background: var(--panel2); border: 1px solid var(--line); border-radius: 11px; padding: 18px; }
.art-grid2 .ag .ag-icon { font-size: 24px; margin-bottom: 9px; }
.art-grid2 .ag h4 { font-size: 14.5px; font-weight: 700; margin-bottom: 6px; color: var(--ink); }
.art-grid2 .ag p  { font-size: 13.5px; color: var(--ink-dim); line-height: 1.6; }

/* ── Related ── */
.art-related { margin-top: 56px; padding-top: 28px; border-top: 1px solid var(--line); }
.art-related h3 { font-size: 16px; font-weight: 700; margin-bottom: 14px; }
.art-related-links { display: flex; gap: 10px; flex-wrap: wrap; }
.art-related-links a {
  padding: 8px 16px; border-radius: 9px; border: 1px solid var(--line);
  font-size: 13.5px; font-weight: 600; color: var(--ink-dim);
  transition: border-color .12s, color .12s;
}
.art-related-links a:hover { border-color: var(--accent); color: var(--accent); }

@media (max-width: 600px) {
  #page { padding: 32px 18px 80px; }
  .art-header h1 { font-size: 27px; }
  .art-grid2 { grid-template-columns: 1fr; }
}