:root {
  --bg-color: #fafafa;
  --card-bg: #ffffff;
  --text-primary: #171717;
  --text-secondary: #525252;
  --accent: #262626;
  --accent-hover: #000000;
  --border-color: #e5e5e5;
  --container-width: 1000px;
  --content-width: 760px;
  --sidebar-width: 260px;
  --toc-width: 200px;
  --header-height: 80px;
  --code-bg: #f4f4f4;
  --code-border: #e5e5e5;
  --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

html { scroll-behavior: smooth; }

body {
  background-color: var(--bg-color);
  color: var(--text-primary);
  font-family: 'Ubuntu', sans-serif;
  letter-spacing: -0.01em;
  line-height: 1.6;
  overflow-x: hidden;
}

h1, h2, h3, h4, h5, h6 {
  font-family: 'Ubuntu', sans-serif;
  font-weight: 700;
  letter-spacing: -0.02em;
}

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

.container {
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 0 2rem;
}

/* ---------- Prose (Markdown content) ---------- */
.prose {
  max-width: var(--content-width);
  margin: 0 auto;
  padding: 1rem 0 4rem;
}

.prose h1 { font-size: 2.25rem; margin: 0 0 1rem; }
.prose h2 { font-size: 1.6rem; margin: 2.5rem 0 1rem; padding-bottom: .4rem; border-bottom: 1px solid var(--border-color); }
.prose h3 { font-size: 1.25rem; margin: 2rem 0 .75rem; }
.prose h4 { font-size: 1.05rem; margin: 1.5rem 0 .5rem; }
.prose p, .prose ul, .prose ol, .prose blockquote { margin: 0 0 1rem; }
.prose ul, .prose ol { padding-left: 1.5rem; }
.prose li > ul, .prose li > ol { margin: .5rem 0; }
.prose img { max-width: 100%; height: auto; border-radius: 8px; }
.prose hr { border: 0; border-top: 1px solid var(--border-color); margin: 2.5rem 0; }
.prose a { text-decoration: none; border-bottom: 1px solid currentColor; }
.prose a:hover { color: var(--accent-hover); }

.prose .headerlink {
  color: var(--text-secondary);
  text-decoration: none;
  border: 0;
  margin-left: .5rem;
  opacity: 0;
  transition: opacity .2s ease;
}
.prose h1:hover .headerlink,
.prose h2:hover .headerlink,
.prose h3:hover .headerlink,
.prose h4:hover .headerlink { opacity: 1; }

/* Definition lists */
.prose dl { margin: 0 0 1rem; }
.prose dt { font-weight: 600; margin-top: 1rem; }
.prose dd { margin-left: 1.5rem; color: var(--text-secondary); }

/* Footnotes */
.prose .footnote { font-size: 0.9rem; color: var(--text-secondary); margin-top: 3rem; }

/* ---------- 404 ---------- */
.not-found { text-align: center; padding: 4rem 0; }
.not-found h1 { font-size: 6rem; margin-bottom: 1rem; }
.not-found .tagline { color: var(--text-secondary); margin-bottom: 2rem; }

/* ---------- Footer ---------- */
.site-footer {
  padding: 4rem 0;
  text-align: center;
  border-top: 1px solid var(--border-color);
  color: var(--text-secondary);
  font-size: 0.9rem;
}

.social-links { margin-bottom: 1rem; }
.social-links a {
  color: var(--text-secondary);
  text-decoration: none;
  margin: 0 1rem;
  transition: var(--transition);
  display: inline-flex;
  vertical-align: middle;
}
.social-links a:hover { color: var(--accent); }

@media (max-width: 640px) {
  .container { padding: 0 1rem; }
  .prose h1 { font-size: 1.75rem; }
}