:root {
  --bg: #ffffff;
  --ink: #12306b;
  --blue: #1d4ed8;
  --blue-deep: #1e3a8a;
  --muted: #34548f;
  --faint: #5a73a3;
  --rule: #dbe3f1;
  --rule-strong: #b6c7ea;
  --tint: #f5f8fe;
  --max: 48rem;
  --index-top: 4rem;
  --zoom-backdrop: rgba(255, 255, 255, 0.94);
}

.theme-toggle,
.to-top {
  font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 0.78rem;
  font-weight: 500;
  letter-spacing: 0.02em;
  color: var(--blue);
  background: var(--bg);
  border: 1px solid var(--rule-strong);
  border-radius: 6px;
  padding: 0.4rem 0.85rem;
  box-shadow: 0 1px 2px rgba(18, 48, 107, 0.06);
  transition: color 0.15s ease, background 0.15s ease, border-color 0.15s ease;
}

.theme-toggle:hover,
.to-top:hover {
  color: #fff;
  background: var(--blue);
  border-color: var(--blue);
}

body {
  margin: 0;
  color: var(--ink);
  font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 18px;
  line-height: 1.7;
  background: var(--bg);
  min-height: 100vh;
}

a {
  color: var(--blue);
  text-decoration: none;
  border-bottom: 1px solid rgba(29, 78, 216, 0.3);
  transition: color 0.15s ease, border-color 0.15s ease;
}

a:hover {
  color: var(--blue-deep);
  border-bottom-color: var(--blue-deep);
}

.sheet {
  max-width: var(--max);
  margin: 0 auto;
  padding: 4rem 1.5rem 6rem;
}

hr {
  border: 0;
  height: 0;
  margin: 2.5rem 0;
  border-top: 1px solid var(--rule);
}

/* ===== Site header ===== */
.site-header {
  text-align: left;
}

.site-title {
  font-size: 2.6rem;
  line-height: 1.1;
  margin: 0 0 0.5rem;
  letter-spacing: -0.02em;
  font-weight: 700;
  color: var(--blue);
}

.site-tagline {
  margin: 0 0 0.5rem;
  color: var(--muted);
}

.meta {
  margin: 0;
  font-size: 0.85rem;
  color: var(--faint);
}

/* ===== Posts ===== */
.posts {
  display: flex;
  flex-direction: column;
  gap: 2rem;
}

.post {
  position: relative;
  padding: 1.6rem 1.6rem 1.4rem;
  background: var(--bg);
  border: 1px solid var(--rule);
  border-radius: 10px;
  box-shadow: 0 1px 2px rgba(18, 48, 107, 0.04);
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.post:hover {
  border-color: var(--rule-strong);
  box-shadow: 0 6px 20px -10px rgba(29, 78, 216, 0.25);
}

.post:target {
  border-color: var(--blue);
}

.eyebrow {
  margin: 0 0 0.5rem;
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--blue);
}

.post-title {
  font-size: 1.45rem;
  line-height: 1.3;
  margin: 0 0 0.35rem;
  font-weight: 700;
  letter-spacing: -0.01em;
}

.post-title a {
  color: var(--ink);
  border-bottom: none;
}

.post-title a:hover {
  color: var(--blue);
}

.post-meta {
  margin: 0 0 0.9rem;
  font-size: 0.85rem;
  color: var(--faint);
}

.post-summary {
  margin: 0 0 0.9rem;
  color: var(--ink);
}

.post-summary img {
  border-radius: 4px;
}

.post-tags {
  margin: 0 0 1rem;
  font-size: 0.85rem;
  color: var(--muted);
}

.post-readmore {
  margin: 0;
  font-size: 0.92rem;
  font-weight: 600;
}

.post-readmore a {
  border-bottom: none;
}

.post-readmore a:hover {
  border-bottom: 1px solid var(--blue-deep);
}

/* ===== Post index ===== */
.post-index {
  margin: 0 0 2.5rem;
  font-family: "JetBrains Mono", "Consolas", monospace;
  font-size: 0.76rem;
  line-height: 1.45;
}

.post-index-title {
  margin: 0 0 0.7rem;
  font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--blue);
}

.post-index-list li {
  margin: 0 0 0.45rem;
}

.post-index-list a {
  color: var(--muted);
}

.post-index-list a:hover {
  color: var(--blue);
}

.post-index-date {
  color: var(--faint);
}

/* ===== Picture zoom ===== */
.zoom-img {
  border-radius: 4px;
  box-shadow: 0 20px 60px -20px rgba(18, 48, 107, 0.45);
}

/* ===== Responsive ===== */
@media (max-width: 36rem) {
  .sheet {
    padding: 2.5rem 1.2rem 4rem;
  }

  .site-title {
    font-size: 2.1rem;
  }

  .post {
    padding: 1.3rem 1.2rem 1.1rem;
  }

  .post-title {
    font-size: 1.25rem;
  }
}