:root {
  color-scheme: light;
  --ink: #1b1b18;
  --muted: #5b564d;          /* darkened for WCAG AA on small text */
  --muted-2: #4a453d;
  --soft: #f6f3ed;
  --paper: #fbfaf7;
  --panel: #ffffff;
  --line: #e6e1d7;
  --line-strong: #d8d2c6;
  --accent: #1f5f5b;
  --accent-2: #8d5132;
  --accent-soft: #e4f0ed;
  --shadow: 0 14px 38px rgba(42, 35, 25, 0.09);
  --shadow-sm: 0 2px 10px rgba(42, 35, 25, 0.05);
  --focus: #0b5c57;
  --wrap: 760px;             /* reading column width */
  --wrap-wide: 1080px;       /* header width */
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  line-height: 1.75;
}
a { color: inherit; }
img { max-width: 100%; height: auto; }

/* --- keyboard accessibility --- */
.skip-link { position: absolute; left: -9999px; top: 0; z-index: 200; }
.skip-link:focus {
  left: 12px; top: 12px;
  padding: 10px 14px;
  background: #fff;
  border: 2px solid var(--accent);
  border-radius: 8px;
  color: var(--accent);
  font-weight: 700;
  text-decoration: none;
}
:focus-visible { outline: 3px solid var(--focus); outline-offset: 2px; border-radius: 4px; }
a:focus:not(:focus-visible), button:focus:not(:focus-visible) { outline: none; }

/* --- top navigation bar --- */
.site-header {
  position: sticky; top: 0; z-index: 100;
  background: rgba(251, 250, 247, 0.88);
  backdrop-filter: saturate(150%) blur(8px);
  -webkit-backdrop-filter: saturate(150%) blur(8px);
  border-bottom: 1px solid var(--line);
}
.header-inner {
  max-width: var(--wrap-wide); margin: 0 auto;
  padding: 0 24px; min-height: 64px;
  display: flex; align-items: center; justify-content: space-between;
  gap: 12px 24px; flex-wrap: wrap;
}
.brand { display: inline-flex; align-items: baseline; gap: 10px; padding: 12px 0; text-decoration: none; color: var(--ink); }
.brand-name { font-size: 19px; font-weight: 760; letter-spacing: .01em; }
.brand-tag { font-size: 12.5px; color: var(--muted); font-weight: 500; }
.site-nav { display: flex; flex-wrap: wrap; gap: 2px; }
.site-nav a {
  display: inline-flex; align-items: center;
  padding: 8px 13px; border-radius: 8px;
  color: var(--muted-2); text-decoration: none;
  font-size: 14.5px; font-weight: 600; line-height: 1.2;
  transition: background-color .15s ease, color .15s ease;
}
.site-nav a:hover { color: var(--accent); background: var(--accent-soft); }
.site-nav a.active, .site-nav a[aria-current="page"] { color: var(--accent); background: var(--accent-soft); }

/* --- layout: left article sidebar + main --- */
.layout {
  display: grid;
  grid-template-columns: 264px minmax(0, 1fr);
  gap: 44px;
  max-width: var(--wrap-wide);
  margin: 0 auto;
  padding: 0 24px;
}
.main { min-width: 0; padding-bottom: 8px; }
.hero, .article-shell, .summary-grid, .breadcrumb, .site-foot {
  max-width: var(--wrap); margin-left: auto; margin-right: auto;
}

/* --- left sidebar: all articles, newest first --- */
.sidebar {
  align-self: start;
  position: sticky; top: 64px;
  max-height: calc(100vh - 64px);
  overflow-y: auto;
  padding: 30px 0 24px;
}
.sidebar h2 {
  margin: 0 0 14px; font-size: 12px; font-weight: 700;
  letter-spacing: .08em; text-transform: uppercase; color: var(--muted);
}
.sidebar-nav { display: grid; gap: 3px; }
.sidebar-nav a {
  display: block; padding: 10px 12px; border-radius: 8px;
  color: var(--muted-2); text-decoration: none;
  font-size: 13.5px; line-height: 1.5;
  transition: background-color .15s ease, color .15s ease;
}
.sidebar-nav a:hover { background: var(--accent-soft); color: var(--accent); }
.sidebar-nav a.active, .sidebar-nav a[aria-current="page"] {
  background: var(--accent-soft); color: var(--accent); font-weight: 700;
}

/* --- cover images --- */
.card-cover {
  display: block; width: 100%; aspect-ratio: 2 / 1; object-fit: cover;
  border-radius: 10px; border: 1px solid var(--line); background: var(--soft);
}
.article-cover {
  display: block; width: 100%; aspect-ratio: 2 / 1; object-fit: cover;
  border-radius: 14px; border: 1px solid var(--line); background: var(--soft);
  margin: 0 0 26px;
}

/* --- home hero --- */
.hero { padding: 54px 0 6px; }
.kicker { margin: 0 0 12px; color: var(--accent-2); font-size: 12.5px; font-weight: 700; letter-spacing: .08em; text-transform: uppercase; }
h1 { margin: 0; font-size: clamp(29px, 4vw, 42px); line-height: 1.18; letter-spacing: -.01em; }
.lede { max-width: 60ch; margin: 18px 0 0; color: var(--muted-2); font-size: 17.5px; }

/* --- home post list --- */
.summary-grid { display: grid; gap: 20px; margin-top: 32px; }
.summary-card {
  display: grid; gap: 12px;
  padding: 28px 28px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: var(--panel);
  box-shadow: var(--shadow-sm);
  transition: transform .18s ease, box-shadow .18s ease, border-color .18s ease;
}
.summary-card:hover { transform: translateY(-2px); box-shadow: var(--shadow); border-color: var(--line-strong); }
.summary-card h2 { margin: 0; font-size: 22px; line-height: 1.4; }
.summary-card h2 a { text-decoration: none; color: var(--ink); }
.summary-card h2 a:hover { color: var(--accent); }
.post-meta { margin: 0; font-size: 13px; color: var(--muted); }
.summary-card p { margin: 0; color: #3a352e; }
.summary-card ul { margin: 2px 0 0; padding-left: 20px; color: var(--muted-2); font-size: 14.5px; }
.summary-card li + li { margin-top: 6px; }
.card-actions { display: flex; align-items: center; gap: 16px; padding-top: 4px; }
.read-link {
  display: inline-flex; align-items: center; gap: 6px;
  color: var(--accent); font-size: 14.5px; font-weight: 700; text-decoration: none;
}
.read-link::after { content: "\2192"; transition: transform .15s ease; }
.read-link:hover { color: var(--accent-2); }
.read-link:hover::after { transform: translateX(3px); }

/* --- breadcrumb --- */
.breadcrumb { padding-top: 28px; font-size: 13px; color: var(--muted); }
.breadcrumb ol { list-style: none; display: flex; flex-wrap: wrap; gap: 6px; margin: 0; padding: 0; }
.breadcrumb a { color: var(--accent); text-decoration: none; }
.breadcrumb a:hover { text-decoration: underline; }
.breadcrumb li + li::before { content: "/"; margin-right: 6px; color: var(--line-strong); }

/* --- article --- */
.article-shell { padding-top: 8px; }
.article-head { padding: 10px 0 24px; border-bottom: 1px solid var(--line); }
.article-head h1 { font-size: clamp(26px, 3.6vw, 38px); line-height: 1.22; }
.article-summary { max-width: 62ch; margin: 18px 0 0; color: var(--muted-2); font-size: 16.5px; }
.article-meta { margin: 16px 0 0; font-size: 13.5px; color: var(--muted); }
.article-meta time { color: var(--muted); }

.toc { margin: 28px 0 0; padding: 20px 22px; border: 1px solid var(--line); border-radius: 12px; background: var(--soft); }
.toc h2 { margin: 0 0 10px; font-size: 12.5px; color: var(--muted); font-weight: 700; letter-spacing: .06em; text-transform: uppercase; }
.toc ol { margin: 0; padding-left: 20px; }
.toc li { margin: 5px 0; }
.toc a { color: var(--accent); text-decoration: none; }
.toc a:hover { text-decoration: underline; }

.article-body { margin: 32px 0 0; color: #221f1a; font-size: 17px; line-height: 1.9; }
.article-body section { scroll-margin-top: 84px; }
.article-body h2 { margin: 42px 0 12px; font-size: 24px; line-height: 1.32; scroll-margin-top: 84px; }
.article-body h2:first-child, .article-body section:first-child h2 { margin-top: 6px; }
.article-body h3 { margin: 28px 0 8px; font-size: 19px; line-height: 1.4; scroll-margin-top: 84px; }
.article-body p { margin: 0 0 16px; }
.article-body ul { margin: 0 0 16px; padding-left: 22px; }
.article-body li { margin: 7px 0; }
.article-body a { color: var(--accent); font-weight: 600; text-decoration: underline; text-underline-offset: 2px; text-decoration-color: rgba(31, 95, 91, .45); }
.article-body a:hover { color: var(--accent-2); text-decoration-color: currentColor; }

.related { margin: 46px 0 0; padding-top: 26px; border-top: 1px solid var(--line); }
.related h2 { margin: 0 0 14px; font-size: 17px; }
.related ul { list-style: none; margin: 0; padding: 0; display: grid; gap: 10px; }
.related a { color: var(--accent); font-weight: 600; text-decoration: none; }
.related a:hover { text-decoration: underline; }

.back-row { margin-top: 32px; }
.back-row a { color: var(--accent); font-weight: 700; text-decoration: none; }
.back-row a:hover { text-decoration: underline; }

/* --- footer --- */
.site-foot { margin: 60px auto 0; padding: 24px 0 44px; border-top: 1px solid var(--line); font-size: 13px; color: var(--muted); }
.site-foot p { margin: 0 0 6px; }
.site-foot a { color: var(--accent); text-decoration: none; }
.site-foot a:hover { text-decoration: underline; }

/* --- responsive --- */
@media (max-width: 880px) {
  .layout { grid-template-columns: 1fr; gap: 0; }
  .sidebar { display: none; }
}
@media (max-width: 720px) {
  .header-inner { padding: 6px 16px; min-height: 0; gap: 4px 16px; }
  .brand { padding: 6px 0; }
  .site-nav a { padding: 7px 10px; font-size: 14px; }
  .layout { padding: 0 16px; }
  .hero { padding: 34px 0 4px; }
  .lede { font-size: 16.5px; }
  .summary-card { padding: 22px 20px; border-radius: 12px; }
  .summary-card h2 { font-size: 20px; }
  .article-body { font-size: 16px; line-height: 1.85; }
  .article-body h2 { font-size: 21px; }
  .article-body h3 { font-size: 18px; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .summary-card, .read-link::after { transition: none; }
}