:root {
  --bg: #080b10;
  --bg-elevated: #0c1017;
  --surface: #111722;
  --surface2: #171e2b;
  --surface3: #1c2535;
  --border: #273244;
  --border-soft: rgba(39, 50, 68, 0.7);
  --text: #eef3fb;
  --muted: #8b9bb0;
  --muted-2: #6b7c91;
  --accent: #5b9cff;
  --accent-soft: rgba(91, 156, 255, 0.14);
  --accent-glow: rgba(91, 156, 255, 0.35);
  --accent-hover: #7eb0ff;
  --ok: #3ecf8e;
  --ok-soft: rgba(62, 207, 142, 0.12);
  --ok-border: rgba(62, 207, 142, 0.3);
  --danger: #ff6b7a;
  --danger-soft: rgba(255, 107, 122, 0.12);
  --danger-border: rgba(255, 107, 122, 0.3);
  --radius: 12px;
  --radius-sm: 8px;
  --radius-lg: 16px;
  --shadow: 0 0 0 1px rgba(255,255,255,0.03), 0 12px 40px rgba(0,0,0,0.35);
  --font: ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", monospace;
  --focus: 0 0 0 3px rgba(91, 156, 255, 0.35);
  --body-glow-1: rgba(91, 156, 255, 0.12);
  --body-glow-2: rgba(99, 102, 241, 0.06);
  --steps-bg: rgba(17, 23, 34, 0.7);
  --step-num-border: rgba(91, 156, 255, 0.25);
  --faq-open-border: #334155;
  --skip-text: #061018;
  --btn-primary-top: #6ba6ff;
  --btn-primary-text: #061018;
  --btn-primary-inset: rgba(255,255,255,0.2);
  --warn-soft: rgba(251, 191, 36, 0.1);
  --warn-border: rgba(251, 191, 36, 0.35);
  --warn-text: #fbbf24;
  --code-bg: #06090e;
}

@media (prefers-color-scheme: light) {
  :root {
    --bg: #f4f6fa;
    --bg-elevated: #ffffff;
    --surface: #ffffff;
    --surface2: #f0f3f8;
    --surface3: #e6ebf3;
    --border: #d0d7e2;
    --border-soft: rgba(176, 188, 206, 0.65);
    --text: #0f172a;
    --muted: #5a6b80;
    --muted-2: #7a8ba0;
    --accent: #3b82f6;
    --accent-soft: rgba(59, 130, 246, 0.12);
    --accent-glow: rgba(59, 130, 246, 0.28);
    --accent-hover: #2563eb;
    --ok: #059669;
    --ok-soft: rgba(5, 150, 105, 0.1);
    --ok-border: rgba(5, 150, 105, 0.35);
    --danger: #e11d48;
    --danger-soft: rgba(225, 29, 72, 0.1);
    --danger-border: rgba(225, 29, 72, 0.3);
    --shadow: 0 0 0 1px rgba(15, 23, 42, 0.04), 0 12px 40px rgba(15, 23, 42, 0.08);
    --focus: 0 0 0 3px rgba(59, 130, 246, 0.3);
    --body-glow-1: rgba(59, 130, 246, 0.1);
    --body-glow-2: rgba(99, 102, 241, 0.05);
    --steps-bg: rgba(255, 255, 255, 0.9);
    --step-num-border: rgba(59, 130, 246, 0.3);
    --faq-open-border: #b6c2d4;
    --skip-text: #ffffff;
    --btn-primary-top: #60a5fa;
    --btn-primary-text: #ffffff;
    --btn-primary-inset: rgba(255,255,255,0.25);
    --warn-soft: rgba(217, 119, 6, 0.1);
    --warn-border: rgba(217, 119, 6, 0.35);
    --warn-text: #b45309;
    --code-bg: #f1f5f9;
  }
}

* { box-sizing: border-box; }
html {
  color-scheme: light dark;
  scroll-behavior: smooth;
}
body {
  margin: 0;
  font-family: var(--font);
  background:
    radial-gradient(ellipse 80% 50% at 50% -20%, var(--body-glow-1), transparent 55%),
    radial-gradient(ellipse 60% 40% at 100% 0%, var(--body-glow-2), transparent 45%),
    var(--bg);
  color: var(--text);
  line-height: 1.55;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
}
a {
  color: var(--accent);
  text-decoration: none;
  transition: color 0.15s ease;
}
a:hover { color: var(--accent-hover); text-decoration: underline; }
code {
  font-family: var(--mono);
  font-size: 0.9em;
  background: var(--surface2);
  border: 1px solid var(--border-soft);
  border-radius: 4px;
  padding: 0.1em 0.35em;
}
.wrap {
  max-width: 780px;
  margin: 0 auto;
  padding: 1.25rem 1.15rem 3.5rem;
}

.topnav {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  margin-bottom: 1.5rem;
  padding-bottom: 0.85rem;
  border-bottom: 1px solid var(--border-soft);
  font-size: 0.88rem;
}
.topnav .brand {
  font-weight: 650;
  color: var(--text);
  text-decoration: none;
}
.topnav .brand:hover { color: var(--accent); text-decoration: none; }
.topnav nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem 1rem;
}
.topnav nav a { color: var(--muted); }
.topnav nav a:hover { color: var(--accent-hover); }

.badge {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--ok);
  border: 1px solid var(--ok-border);
  background: var(--ok-soft);
  padding: 0.28rem 0.7rem;
  border-radius: 999px;
  margin-bottom: 0.85rem;
}

header.hero { margin-bottom: 1.5rem; }
h1 {
  font-size: clamp(1.55rem, 4vw, 2rem);
  line-height: 1.2;
  letter-spacing: -0.025em;
  margin: 0 0 0.65rem;
  font-weight: 700;
}
.h1-cn {
  font-size: clamp(1.15rem, 3vw, 1.35rem);
  font-weight: 600;
  color: var(--muted);
  margin: -0.35rem 0 0.85rem;
  letter-spacing: -0.01em;
}
.lede {
  color: var(--muted);
  margin: 0 0 0.65rem;
  font-size: 1.02rem;
  max-width: 42rem;
  line-height: 1.55;
}
.lede-cn {
  color: var(--muted-2);
  margin: 0;
  font-size: 0.95rem;
  max-width: 42rem;
  line-height: 1.55;
}

article section {
  margin-bottom: 2rem;
}
.section-label {
  font-size: 0.7rem;
  font-weight: 650;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted-2);
  margin: 0 0 0.45rem;
}
h2 {
  font-size: 1.15rem;
  letter-spacing: -0.015em;
  margin: 0 0 0.35rem;
  font-weight: 650;
}
.h2-cn {
  font-size: 0.95rem;
  font-weight: 550;
  color: var(--muted);
  margin: 0 0 0.75rem;
}
h3 {
  font-size: 0.98rem;
  margin: 1rem 0 0.4rem;
  font-weight: 600;
}
p { margin: 0 0 0.85rem; color: var(--muted); }
p.strong { color: var(--text); }
ul, ol {
  margin: 0 0 0.85rem;
  padding-left: 1.25rem;
  color: var(--muted);
}
li { margin-bottom: 0.4rem; }
li strong { color: var(--text); }

.answer-box {
  background: var(--surface);
  border: 1px solid var(--border-soft);
  border-radius: var(--radius);
  padding: 1.1rem 1.2rem;
  margin-bottom: 1.75rem;
  box-shadow: var(--shadow);
}
.answer-box .lede { color: var(--text); }
.answer-box .lede-cn { margin-top: 0.75rem; padding-top: 0.75rem; border-top: 1px solid var(--border-soft); }

.callout {
  background: var(--warn-soft);
  border: 1px solid var(--warn-border);
  border-radius: var(--radius-sm);
  padding: 0.95rem 1.05rem;
  margin: 0.85rem 0 1rem;
}
.callout p { margin: 0 0 0.55rem; color: var(--text); font-size: 0.92rem; }
.callout p:last-child { margin-bottom: 0; }
.callout .label {
  font-size: 0.68rem;
  font-weight: 650;
  letter-spacing: 0.07em;
  text-transform: uppercase;
  color: var(--warn-text);
  margin-bottom: 0.4rem;
}
.callout .cn { color: var(--muted); font-size: 0.88rem; }

ol.steps {
  margin: 0 0 0.85rem;
  padding: 0;
  list-style: none;
  counter-reset: step;
  display: grid;
  gap: 0.5rem;
}
ol.steps li {
  counter-increment: step;
  padding: 0.85rem 0.95rem;
  background: var(--steps-bg);
  border: 1px solid var(--border-soft);
  border-radius: var(--radius-sm);
  display: grid;
  grid-template-columns: auto 1fr;
  column-gap: 0.75rem;
  align-items: start;
  margin: 0;
}
ol.steps li::before {
  content: counter(step);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 1.45rem;
  height: 1.45rem;
  border-radius: 999px;
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--accent);
  background: var(--accent-soft);
  border: 1px solid var(--step-num-border);
  margin-top: 0.05rem;
}
ol.steps li .step-body { min-width: 0; }
ol.steps li h3 { margin: 0 0 0.2rem; font-size: 0.92rem; color: var(--text); }
ol.steps li p { margin: 0; font-size: 0.85rem; line-height: 1.45; }

.table-wrap {
  overflow-x: auto;
  margin: 0.75rem 0 1rem;
  border: 1px solid var(--border-soft);
  border-radius: var(--radius-sm);
}
table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.88rem;
}
th, td {
  text-align: left;
  padding: 0.7rem 0.85rem;
  border-bottom: 1px solid var(--border-soft);
  vertical-align: top;
}
th {
  background: var(--surface2);
  color: var(--text);
  font-weight: 600;
  font-size: 0.8rem;
}
td { color: var(--muted); }
tr:last-child td { border-bottom: none; }
td strong { color: var(--text); font-weight: 600; }

.cta-box {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem 1.3rem;
  margin: 1.5rem 0 2rem;
  text-align: center;
  box-shadow: var(--shadow);
}
.cta-box h2 { margin-bottom: 0.35rem; }
.cta-box .h2-cn { margin-bottom: 0.75rem; }
.cta-box p { margin: 0 0 1rem; }
.cta-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem;
  justify-content: center;
}
a.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  appearance: none;
  border: 1px solid var(--border);
  background: var(--surface3);
  color: var(--text);
  border-radius: var(--radius-sm);
  padding: 0.72rem 1.15rem;
  font: inherit;
  font-size: 0.92rem;
  font-weight: 500;
  text-decoration: none;
  transition: background 0.15s ease, border-color 0.15s ease, box-shadow 0.15s ease;
}
a.btn:hover { text-decoration: none; border-color: #3d5068; }
a.btn-primary {
  background: linear-gradient(180deg, var(--btn-primary-top) 0%, var(--accent) 100%);
  border-color: transparent;
  color: var(--btn-primary-text);
  font-weight: 700;
  letter-spacing: -0.01em;
  box-shadow: 0 1px 0 var(--btn-primary-inset) inset, 0 4px 16px var(--accent-glow);
  padding: 0.78rem 1.35rem;
}
a.btn-primary:hover {
  color: var(--btn-primary-text);
  text-decoration: none;
  box-shadow: 0 1px 0 var(--btn-primary-inset) inset, 0 6px 20px var(--accent-glow);
}
a.btn-ghost {
  background: transparent;
  color: var(--muted);
  border-color: var(--border-soft);
}
a.btn-ghost:hover { color: var(--text); background: rgba(255,255,255,0.04); text-decoration: none; }

#faq { margin-bottom: 0.5rem; }
#faq > h2 { margin-bottom: 0.25rem; }
#faq > .h2-cn { margin-bottom: 0.75rem; }
details.faq {
  background: var(--surface);
  border: 1px solid var(--border-soft);
  border-radius: var(--radius-sm);
  padding: 0;
  margin-bottom: 0.45rem;
  overflow: hidden;
  transition: border-color 0.15s ease;
}
details.faq:hover { border-color: var(--border); }
details.faq[open] { border-color: var(--faq-open-border); }
details.faq summary {
  cursor: pointer;
  font-weight: 600;
  font-size: 0.92rem;
  padding: 0.8rem 1rem;
  list-style: none;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  color: var(--text);
}
details.faq summary::-webkit-details-marker { display: none; }
details.faq summary::after {
  content: "+";
  color: var(--muted-2);
  font-weight: 400;
  font-size: 1.1rem;
  flex-shrink: 0;
}
details.faq[open] summary::after { content: "−"; }
details.faq .faq-body {
  padding: 0 1rem 0.9rem;
}
details.faq .faq-body p {
  margin: 0 0 0.55rem;
  color: var(--muted);
  font-size: 0.9rem;
  line-height: 1.5;
}
details.faq .faq-body p:last-child { margin-bottom: 0; }
details.faq .faq-cn {
  margin-top: 0.55rem;
  padding-top: 0.55rem;
  border-top: 1px solid var(--border-soft);
  font-size: 0.85rem;
  color: var(--muted-2);
}

footer {
  margin-top: 2.25rem;
  padding-top: 1.15rem;
  border-top: 1px solid var(--border-soft);
  color: var(--muted-2);
  font-size: 0.82rem;
}
footer p { margin: 0 0 0.55rem; color: var(--muted-2); }
footer nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem 1rem;
}
footer nav a {
  color: var(--muted);
  font-size: 0.82rem;
}
footer nav a:hover { color: var(--accent-hover); }

.skip {
  position: absolute;
  left: -9999px;
}
.skip:focus {
  left: 1rem;
  top: 1rem;
  z-index: 10;
  background: var(--accent);
  color: var(--skip-text);
  padding: 0.5rem 0.75rem;
  border-radius: 6px;
  font-weight: 600;
}

.decision {
  background: var(--surface2);
  border: 1px solid var(--border-soft);
  border-radius: var(--radius-sm);
  padding: 1rem 1.1rem;
  margin: 0.75rem 0;
}
.decision ol { margin-bottom: 0; }
.lang-note {
  font-size: 0.78rem;
  color: var(--muted-2);
  margin: 0 0 1rem;
}

/* —— Code blocks, breadcrumbs, related guides —— */
pre.code {
  background: var(--code-bg, var(--bg-elevated));
  border: 1px solid var(--border-soft);
  border-radius: var(--radius-sm);
  padding: 0.85rem 0.95rem;
  overflow-x: auto;
  font-family: var(--mono);
  font-size: 0.76rem;
  line-height: 1.5;
  color: var(--text);
  margin: 0.5rem 0 1rem;
}
pre.code code { background: none; border: 0; padding: 0; font-size: inherit; }
.file-label {
  font-family: var(--mono);
  font-size: 0.74rem;
  color: var(--muted-2);
  margin: 0.75rem 0 -0.25rem;
}
nav.crumbs { font-size: 0.78rem; color: var(--muted-2); margin: -0.5rem 0 1rem; }
nav.crumbs ol { list-style: none; padding: 0; margin: 0; display: flex; flex-wrap: wrap; gap: 0.35rem; color: var(--muted-2); }
nav.crumbs li { margin: 0; }
nav.crumbs li + li::before { content: "›"; margin-right: 0.35rem; }
nav.crumbs a { color: var(--muted); }
.related { margin: 1.5rem 0 2rem; }
.related ul { list-style: none; padding: 0; display: grid; gap: 0.45rem; }
.related li {
  background: var(--surface);
  border: 1px solid var(--border-soft);
  border-radius: var(--radius-sm);
  padding: 0.7rem 0.9rem;
  margin: 0;
  font-size: 0.88rem;
}
.related li a { font-weight: 600; }