:root {
  --bg: #f6f7f9;
  --surface: #ffffff;
  --surface-muted: #f1f4f8;
  --border: #e2e8f0;
  --text: #1e293b;
  --text-body: #334155;
  --muted: #64748b;
  --accent: #1d5bbf;
  --accent-hover: #164a96;
  --accent-soft: rgba(29, 91, 191, 0.12);
  --heading: #0f172a;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text-body);
  font-family: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
}

a {
  color: var(--accent);
  text-decoration: none;
}

a:hover {
  color: var(--accent-hover);
  text-decoration: underline;
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: auto;
  width: 1px;
  height: 1px;
  overflow: hidden;
}

.skip-link:focus {
  left: 1rem;
  top: 1rem;
  width: auto;
  height: auto;
  padding: 0.5rem 0.75rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text);
  z-index: 100;
}

.wrap {
  max-width: 52rem;
  margin: 0 auto;
  padding: 0 1.5rem 3rem;
}

.hero {
  padding: 2.5rem 0 1.4rem;
}

.page-title {
  font-size: clamp(1.85rem, 4.5vw, 2.35rem);
  font-weight: 800;
  line-height: 1.3;
  letter-spacing: -0.02em;
  color: var(--heading);
  display: inline;
  background: linear-gradient(
    to top,
    var(--accent-soft) 0 38%,
    transparent 38% 100%
  );
  -webkit-box-decoration-break: clone;
  box-decoration-break: clone;
  padding: 0 0.06em 0.04em;
  margin: 0 0 1rem;
}

h1.page-title {
  margin: 0 0 1rem;
}

h2 {
  margin: 2.4rem 0 1rem;
  padding-bottom: 0.55rem;
  border-bottom: 1px solid var(--border);
  font-size: 1.28rem;
  font-weight: 700;
  color: var(--heading);
  line-height: 1.35;
}

h3 {
  margin: 1.5rem 0 0.7rem;
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--text);
}

p {
  margin: 0 0 1.1rem;
  color: var(--text-body);
  line-height: 1.82;
}

.lead {
  font-size: 1.08rem;
  color: var(--text);
  line-height: 1.78;
}

.meta {
  color: var(--muted);
  font-size: 0.94rem;
  margin-bottom: 1.35rem;
}

.meta time {
  color: #475569;
}

.toc {
  margin: 1rem 0 2rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.15rem 1.25rem 1rem;
  box-shadow: 0 1px 2px rgba(15, 23, 42, 0.04);
}

.toc-title {
  margin: 0;
  font-weight: 600;
  color: var(--heading);
  font-size: 0.98rem;
}

.toc ol {
  margin: 0.55rem 0 0;
  padding-left: 1.28rem;
  color: var(--text-body);
}

.toc li {
  margin: 0.45rem 0;
}

.tip {
  background: #f0f7ff;
  border: 1px solid #cfe0f8;
  border-left: 4px solid var(--accent);
  border-radius: 10px;
  padding: 1rem 1.15rem;
  margin: 1.35rem 0;
  color: var(--text-body);
}

.note-box {
  background: var(--surface-muted);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 1rem 1.15rem;
  margin: 1.2rem 0;
  color: var(--text-body);
}

.plain-list,
.article ul:not(.related-list) {
  margin: 0 0 1.15rem;
  padding-left: 1.25rem;
  color: var(--text-body);
}

.plain-list li,
.article ul:not(.related-list) li {
  margin-bottom: 0.5rem;
}

ol.step-list {
  margin: 0 0 1.15rem;
  padding-left: 1.35rem;
  color: var(--text-body);
}

ol.step-list li {
  margin-bottom: 1rem;
}

ol.step-list li p {
  margin-top: 0.35rem;
}

.table-wrap {
  overflow-x: auto;
  margin: 1.25rem 0 1.5rem;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--surface);
}

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.92rem;
}

th,
td {
  padding: 0.65rem 0.75rem;
  border-bottom: 1px solid var(--border);
  text-align: left;
  vertical-align: top;
  color: var(--text-body);
}

tr:last-child th,
tr:last-child td {
  border-bottom: none;
}

thead th {
  background: var(--surface-muted);
  color: var(--heading);
  font-weight: 600;
}

.figure {
  margin: 1.25rem 0 1.5rem;
  border: 1px solid var(--border);
  border-radius: 10px;
  overflow: hidden;
  background: var(--surface);
  box-shadow: 0 1px 3px rgba(15, 23, 42, 0.06);
}

.figure img {
  display: block;
  width: 100%;
  height: auto;
}

.figure figcaption {
  padding: 0.75rem 1rem;
  font-size: 0.88rem;
  color: var(--muted);
  line-height: 1.55;
  border-top: 1px solid var(--border);
  background: var(--surface-muted);
}

.kw-link {
  color: var(--accent);
  font-weight: 600;
}

.kw-link:hover {
  color: var(--accent-hover);
}

.related-reading {
  margin-top: 2.5rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border);
}

.related-reading h2 {
  margin-top: 0;
  font-size: 1.12rem;
  border-bottom: none;
  padding-bottom: 0;
}

.related-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.related-list li {
  margin: 0.5rem 0;
}

.faq-item {
  border-bottom: 1px solid var(--border);
  padding: 1.1rem 0;
}

.faq-item:first-of-type {
  padding-top: 0;
}

.faq-item:last-child {
  border-bottom: none;
  padding-bottom: 0;
}

.faq-q {
  font-weight: 600;
  margin: 0 0 0.45rem;
  color: var(--heading);
}

.faq-a {
  margin: 0;
  color: var(--text-body);
  font-size: 0.98rem;
  line-height: 1.75;
}

.site-footer,
.footer {
  margin-top: 3rem;
  border-top: 1px solid var(--border);
  padding: 1.4rem 0 0.5rem;
  color: var(--muted);
  font-size: 0.85rem;
  line-height: 1.65;
}

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

.back-to-top {
  position: fixed;
  right: 1.25rem;
  bottom: 1.25rem;
  z-index: 90;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 2.75rem;
  height: 2.75rem;
  padding: 0;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--surface);
  color: var(--accent);
  box-shadow: 0 4px 14px rgba(15, 23, 42, 0.12);
  cursor: pointer;
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
  transition:
    background 0.15s ease,
    color 0.15s ease,
    border-color 0.15s ease,
    box-shadow 0.15s ease;
}

.back-to-top:hover {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}

.back-to-top:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.back-to-top__icon {
  display: block;
  width: 1.1rem;
  height: 1.1rem;
}

@media (max-width: 640px) {
  .wrap {
    padding: 0 1rem 2.5rem;
  }

  .hero {
    padding: 2rem 0 1.1rem;
  }

  .page-title {
    font-size: clamp(1.65rem, 7vw, 2rem);
    line-height: 1.32;
  }

  h2 {
    margin-top: 2rem;
  }

  p {
    line-height: 1.78;
  }

  .back-to-top {
    right: 1rem;
    bottom: 1rem;
    width: 2.5rem;
    height: 2.5rem;
  }
}