:root {
  --bg: #f6f3ec;
  --surface: #fffdf8;
  --surface-2: #efeae1;
  --text: #1c1917;
  --text-secondary: #3f3a36;
  --muted: #6b645c;
  --accent: #1f4d63;
  --accent-soft: rgba(31, 77, 99, 0.1);
  --accent-hover: #163a4b;
  --border: #ddd4c7;
  --radius: 12px;
  --font-sans: "Source Sans 3", "Segoe UI", system-ui, sans-serif;
  --font-serif: "Source Serif 4", Georgia, serif;
  --content-width: 42rem;
  --header-height: 3.75rem;
}

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

html {
  scroll-behavior: smooth;
  font-size: 18px;
}

body {
  font-family: var(--font-sans);
  background: var(--bg);
  color: var(--text);
  line-height: 1.7;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  -webkit-font-smoothing: antialiased;
}

.progress-bar {
  position: fixed;
  top: 0;
  left: 0;
  height: 3px;
  background: var(--accent);
  width: 0%;
  z-index: 1000;
  transition: width 0.1s linear;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(246, 243, 236, 0.92);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  height: var(--header-height);
  display: flex;
  align-items: center;
}

.site-header .container,
.container {
  width: min(1100px, 94%);
  margin: 0 auto;
}

.site-header .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.site-title {
  font-weight: 700;
  font-size: 1.15rem;
  color: var(--text);
  text-decoration: none;
  letter-spacing: -0.02em;
}

nav {
  display: flex;
  gap: 0.25rem;
}

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

nav a {
  color: var(--muted);
  text-decoration: none;
  font-size: 0.9rem;
  font-weight: 500;
  padding: 0.4rem 0.75rem;
  border-radius: 6px;
  transition: color 0.15s, background 0.15s;
}

nav a:hover {
  color: var(--accent);
  background: var(--accent-soft);
}

main {
  flex: 1;
  padding: 2rem 0 4rem;
}

.hero {
  text-align: left;
  padding: 2.5rem 0 1.5rem;
  max-width: 40rem;
  border-bottom: 1px solid var(--border);
  margin-bottom: 2rem;
}

.hero h1 {
  font-family: var(--font-serif);
  font-size: clamp(1.8rem, 4vw, 2.6rem);
  font-weight: 650;
  letter-spacing: -0.03em;
  line-height: 1.2;
  margin-bottom: 0.75rem;
}

.hero p {
  color: var(--muted);
  font-size: 1.05rem;
  line-height: 1.6;
}

.science-feature {
  margin: 0 0 3rem;
}

.science-feature .section-head h2 {
  font-size: 1.8rem;
  margin-bottom: 0.4rem;
}

.science-feature .section-head h2 a {
  color: var(--text);
  text-decoration: none;
}

.science-feature .section-head h2 a:hover { color: var(--accent); }

.science-feature .section-head p {
  color: var(--muted);
  margin-bottom: 1.5rem;
}

.science-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1.5rem;
}

.science-card,
.section-card,
.post-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.4rem;
}

.science-card h3 {
  font-family: var(--font-serif);
  font-size: 1.15rem;
  margin-bottom: 0.6rem;
  line-height: 1.35;
}

.science-card h3 a,
.post-card h2 a,
.post-card h3 a {
  color: var(--text);
  text-decoration: none;
}

.science-card h3 a:hover,
.post-card h2 a:hover,
.post-card h3 a:hover { color: var(--accent); }

.science-card p,
.summary {
  color: var(--muted);
  font-size: 0.95rem;
  margin-bottom: 0.9rem;
  line-height: 1.6;
}

.sections {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 1.25rem;
  margin: 0 0 3rem;
}

.section-card h2 {
  font-size: 1.1rem;
  margin-bottom: 0.9rem;
}

.section-card h2 a {
  color: var(--accent);
  text-decoration: none;
}

.section-card ul { list-style: none; }
.section-card li { margin: 0.45rem 0; }
.section-card li a {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.92rem;
}
.section-card li a:hover { color: var(--accent); }

.post-list {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.post-card h2, .post-card h3 {
  font-family: var(--font-serif);
  font-size: 1.2rem;
  font-weight: 650;
  letter-spacing: -0.02em;
  margin-bottom: 0.4rem;
  line-height: 1.35;
}

.post-meta {
  font-size: 0.82rem;
  color: var(--muted);
  margin-bottom: 0.65rem;
}

.read-more {
  color: var(--accent);
  text-decoration: none;
  font-size: 0.9rem;
  font-weight: 600;
}

.read-more:hover { color: var(--accent-hover); }

.post {
  max-width: var(--content-width);
  margin: 0 auto;
}

.post-header {
  margin-bottom: 2.25rem;
  padding-bottom: 1.5rem;
  border-bottom: 1px solid var(--border);
}

.post-header h1 {
  font-family: var(--font-serif);
  font-size: clamp(1.7rem, 3.5vw, 2.15rem);
  font-weight: 700;
  line-height: 1.25;
  letter-spacing: -0.025em;
  margin-bottom: 1rem;
  color: var(--text);
}

.post-content {
  font-family: var(--font-serif);
  font-size: 1.08rem;
  line-height: 1.8;
  color: var(--text-secondary);
}

.post-content h2 {
  font-family: var(--font-sans);
  font-size: 1.45rem;
  font-weight: 700;
  color: var(--text);
  margin: 2.75rem 0 1rem;
}

.post-content h3 {
  font-family: var(--font-sans);
  font-size: 1.2rem;
  font-weight: 650;
  color: var(--text);
  margin: 2rem 0 0.75rem;
}

.post-content p { margin-bottom: 1.35rem; }
.post-content ul, .post-content ol { margin: 0 0 1.35rem 1.5rem; }
.post-content li { margin-bottom: 0.5rem; }
.post-content strong { color: var(--text); font-weight: 650; }
.post-content a { color: var(--accent); }

.related-posts {
  margin-top: 3.5rem;
  padding: 1.75rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
}

.related-posts h2 {
  font-size: 1.15rem;
  font-weight: 650;
  margin-bottom: 0.35rem;
}

.related-note {
  font-size: 0.8rem;
  color: var(--muted);
  margin-bottom: 1.1rem;
}

.related-posts > ul { list-style: none; }
.related-posts > ul > li {
  margin-bottom: 1rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--border);
}
.related-posts > ul > li:last-child {
  margin-bottom: 0;
  padding-bottom: 0;
  border-bottom: none;
}
.related-posts > ul > li > a {
  color: var(--accent);
  text-decoration: none;
  font-weight: 600;
}

.matched-headings {
  list-style: none;
  margin: 0.5rem 0 0 0.5rem;
}
.matched-headings a {
  font-size: 0.85rem;
  color: var(--muted);
  text-decoration: none;
}
.matched-headings a:hover { color: var(--accent); }

.post-nav {
  display: flex;
  justify-content: space-between;
  gap: 1.5rem;
  margin-top: 3rem;
  padding-top: 1.75rem;
  border-top: 1px solid var(--border);
}
.post-nav a {
  color: var(--muted);
  text-decoration: none;
  font-size: 0.9rem;
  max-width: 45%;
}
.post-nav a:hover { color: var(--accent); }
.post-nav .next { text-align: right; margin-left: auto; }

.site-footer {
  border-top: 1px solid var(--border);
  padding: 1.75rem 0;
  text-align: center;
  color: var(--muted);
  font-size: 0.82rem;
}

.footer-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.lang-switch {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
}

.lang-switch a {
  min-height: 44px;
  display: inline-flex;
  align-items: center;
  padding: 0.35rem 0.7rem;
  border-radius: 6px;
}

.lang-switch a[aria-current="page"] {
  background: var(--surface-2, #efeae1);
  color: var(--accent);
  font-weight: 600;
}

.list-header {
  margin-bottom: 2.25rem;
  max-width: var(--content-width);
}
.list-header h1 {
  font-size: 1.9rem;
  font-weight: 700;
}
.list-desc {
  color: var(--muted);
  margin-top: 0.5rem;
}
.latest h2 {
  font-size: 1.3rem;
  margin-bottom: 1.25rem;
}

@media (max-width: 640px) {
  html { font-size: 17px; }
  nav a { padding: 0.35rem 0.5rem; font-size: 0.85rem; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .progress-bar { transition: none; }
}