:root {
  --color-bg: #ffffff;
  --color-bg-soft: #f4f4f5;
  --color-text: #18181b;
  --color-muted: #71717a;
  --color-border: #e4e4e7;
  --color-accent: #2563eb;
  --color-accent-soft: #eff6ff;
  --radius: 8px;
  --max-width: 880px;
  --font-sans: system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --font-serif: Georgia, "Times New Roman", serif;
}

* {
  box-sizing: border-box;
}

html {
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: 16px;
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.6;
}

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

a:hover {
  text-decoration: underline;
}

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 16px;
}

/* ---------- Header / nav ---------- */

.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
}

.site-header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
  min-height: 64px;
  padding-top: 8px;
  padding-bottom: 8px;
}

.brand {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--color-text);
  letter-spacing: -0.02em;
}

.brand:hover {
  text-decoration: none;
}

.nav {
  display: flex;
  flex-wrap: wrap;
  gap: 4px;
}

.nav a {
  padding: 6px 12px;
  border-radius: 999px;
  color: var(--color-muted);
  font-weight: 500;
  font-size: 0.95rem;
}

.nav a:hover {
  color: var(--color-text);
  background: var(--color-bg-soft);
  text-decoration: none;
}

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

/* ---------- Home / landing ---------- */

.hero {
  padding: 56px 0 24px;
}

.hero h1 {
  font-size: 2.25rem;
  margin: 0 0 8px;
  letter-spacing: -0.02em;
}

.tagline {
  color: var(--color-muted);
  font-size: 1.1rem;
  margin: 0;
}

.category-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 16px;
  margin: 24px 0;
}

.category-card {
  display: block;
  padding: 20px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background: var(--color-bg-soft);
  color: var(--color-text);
}

.category-card h3 {
  margin: 0 0 6px;
  color: var(--color-accent);
}

.category-card p {
  margin: 0;
  color: var(--color-muted);
  font-size: 0.95rem;
}

.category-card:hover {
  border-color: var(--color-accent);
  text-decoration: none;
}

.about {
  margin: 40px 0;
}

.about p {
  color: var(--color-muted);
}

/* ---------- Category pages ---------- */

.category-title {
  margin: 40px 0 4px;
}

.category-description {
  color: var(--color-muted);
  margin: 0 0 24px;
}

.post-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.post-card {
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 20px 24px;
}

.post-card .post-title {
  margin: 0 0 4px;
  font-size: 1.25rem;
}

.post-card .post-title a {
  color: var(--color-text);
}

.post-card .post-title a:hover {
  color: var(--color-accent);
  text-decoration: none;
}

.post-date {
  color: var(--color-muted);
  font-size: 0.85rem;
}

.post-excerpt {
  margin: 8px 0 0;
  color: var(--color-muted);
}

.post-list .empty {
  color: var(--color-muted);
  padding: 24px;
  border: 1px dashed var(--color-border);
  border-radius: var(--radius);
}

/* ---------- Post pages ---------- */

.post-header {
  margin: 40px 0 8px;
}

.post-header h1 {
  font-size: 1.9rem;
  margin: 4px 0 8px;
  line-height: 1.25;
}

.post-category {
  margin: 0 0 4px;
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

.post-category a {
  font-weight: 600;
}

.post-body {
  font-family: var(--font-serif);
  font-size: 1.1rem;
}

.post-body h2,
.post-body h3,
.post-body h4 {
  font-family: var(--font-sans);
}

.post-body img {
  max-width: 100%;
  height: auto;
  border-radius: var(--radius);
}

.post-body blockquote {
  border-left: 3px solid var(--color-accent);
  margin: 0;
  padding: 2px 16px;
  color: var(--color-muted);
}

.post-body code {
  background: var(--color-bg-soft);
  padding: 2px 4px;
  border-radius: 4px;
  font-size: 0.9em;
}

.post-body pre {
  background: var(--color-bg-soft);
  padding: 12px 16px;
  border-radius: var(--radius);
  overflow-x: auto;
}

.back-link {
  margin: 32px 0;
}

/* ---------- Footer ---------- */

.site-footer {
  border-top: 1px solid var(--color-border);
  margin-top: 48px;
  padding: 24px 0;
  color: var(--color-muted);
  font-size: 0.9rem;
}

.site-footer p {
  margin: 0;
}

/* ---------- Small screens ---------- */

@media (max-width: 560px) {
  .site-header .container {
    justify-content: center;
    text-align: center;
  }

  .nav {
    justify-content: center;
  }

  .hero h1 {
    font-size: 1.75rem;
  }
}