@import url('https://fonts.googleapis.com/css2?family=Playfair+Display:ital,wght@0,700;0,900;1,700&family=IBM+Plex+Mono:wght@400;500&family=Source+Serif+4:ital,opsz,wght@0,8..60,400;0,8..60,600;1,8..60,400&display=swap');

:root {
  --bg: #0d0e0f;
  --surface: #141517;
  --surface2: #1c1e21;
  --border: #2a2d32;
  --accent: #e8633a;
  --accent2: #f0a500;
  --text: #d4cfc8;
  --text-dim: #7a7670;
  --text-muted: #4a4845;
  --heading: #ede9e3;
  --code-bg: #181a1d;
  --code-border: #2f3238;
  --tag-bg: #1e2024;
  --serif: 'Source Serif 4', Georgia, serif;
  --display: 'Playfair Display', serif;
  --mono: 'IBM Plex Mono', 'Courier New', monospace;
  --max-w: 720px;
}

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

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

body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--serif);
  font-size: 1rem;
  line-height: 1.8;
  -webkit-font-smoothing: antialiased;
}

/* ── SITE HEADER ── */
.site-header {
  border-bottom: 1px solid var(--border);
  padding: 1.5rem 2rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  position: sticky;
  top: 0;
  background: rgba(13,14,15,0.92);
  backdrop-filter: blur(12px);
  z-index: 100;
}

.site-logo {
  font-family: var(--mono);
  font-size: 0.82rem;
  font-weight: 500;
  letter-spacing: 0.08em;
  color: var(--accent);
  text-decoration: none;
  text-transform: uppercase;
}

.site-logo span {
  color: var(--text-dim);
}

.site-nav a {
  font-family: var(--mono);
  font-size: 0.75rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--text-dim);
  text-decoration: none;
  margin-left: 2rem;
  transition: color 0.2s;
}
.site-nav a:hover { color: var(--heading); }

/* ── HOME / INDEX ── */
.home-hero {
  max-width: 860px;
  margin: 0 auto;
  padding: 5rem 2rem 3rem;
  border-bottom: 1px solid var(--border);
}

.home-hero-label {
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 1.5rem;
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.home-hero-label::before {
  content: '';
  display: inline-block;
  width: 24px;
  height: 1px;
  background: var(--accent);
}

.home-hero h1 {
  font-family: var(--display);
  font-size: clamp(2.4rem, 5vw, 3.8rem);
  font-weight: 900;
  color: var(--heading);
  line-height: 1.1;
  margin-bottom: 1.5rem;
}

.home-hero h1 em {
  color: var(--accent);
  font-style: italic;
}

.home-hero p {
  font-size: 1.05rem;
  color: var(--text-dim);
  max-width: 560px;
  line-height: 1.7;
}

/* ── POST LIST ── */
.post-list-section {
  max-width: 860px;
  margin: 0 auto;
  padding: 3rem 2rem 6rem;
}

.section-label {
  font-family: var(--mono);
  font-size: 0.7rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--text-muted);
  margin-bottom: 2rem;
  padding-bottom: 0.75rem;
  border-bottom: 1px solid var(--border);
}

.post-item {
  display: grid;
  grid-template-columns: 80px 1fr;
  gap: 0 2rem;
  padding: 2rem 0;
  border-bottom: 1px solid var(--border);
  text-decoration: none;
  color: inherit;
  transition: background 0.15s;
}

.post-item:hover .post-title { color: var(--accent); }

.post-date-col {
  font-family: var(--mono);
  font-size: 0.7rem;
  color: var(--text-muted);
  letter-spacing: 0.04em;
  padding-top: 0.3rem;
  line-height: 1.4;
}

.post-title {
  font-family: var(--display);
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--heading);
  line-height: 1.25;
  margin-bottom: 0.5rem;
  transition: color 0.2s;
}

.post-excerpt {
  font-size: 0.9rem;
  color: var(--text-dim);
  line-height: 1.6;
  margin-bottom: 0.75rem;
}

.post-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
}

.tag {
  font-family: var(--mono);
  font-size: 0.65rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  background: var(--tag-bg);
  color: var(--text-muted);
  border: 1px solid var(--border);
  padding: 0.15rem 0.55rem;
  border-radius: 2px;
}

.tag.accent { color: var(--accent); border-color: var(--accent); background: rgba(232,99,58,0.08); }
.tag.gold { color: var(--accent2); border-color: var(--accent2); background: rgba(240,165,0,0.08); }

/* ── POST LAYOUT ── */
.post-container {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 4rem 2rem 8rem;
}

.post-header {
  margin-bottom: 3.5rem;
  padding-bottom: 2rem;
  border-bottom: 1px solid var(--border);
}

.post-header-label {
  font-family: var(--mono);
  font-size: 0.7rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 1.2rem;
  display: flex;
  align-items: center;
  gap: 0.6rem;
}

.post-header-label::before {
  content: '//';
  color: var(--text-muted);
}

.post-title-large {
  font-family: var(--display);
  font-size: clamp(1.9rem, 4vw, 2.8rem);
  font-weight: 900;
  color: var(--heading);
  line-height: 1.15;
  margin-bottom: 1.5rem;
}

.post-meta {
  display: flex;
  align-items: center;
  gap: 1.5rem;
  font-family: var(--mono);
  font-size: 0.72rem;
  color: var(--text-muted);
  flex-wrap: wrap;
}

.post-meta-dot { color: var(--border); }

/* ── ARTICLE CONTENT ── */
.post-content {
  font-size: 1rem;
  line-height: 1.85;
}

.post-content h2 {
  font-family: var(--display);
  font-size: 1.6rem;
  font-weight: 700;
  color: var(--heading);
  margin: 3rem 0 1rem;
  line-height: 1.2;
}

.post-content h3 {
  font-family: var(--mono);
  font-size: 0.82rem;
  font-weight: 500;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent2);
  margin: 2.5rem 0 0.75rem;
}

.post-content p { margin-bottom: 1.4rem; }

.post-content a {
  color: var(--accent);
  text-decoration: underline;
  text-underline-offset: 3px;
}

.post-content strong {
  color: var(--heading);
  font-weight: 600;
}

.post-content em { font-style: italic; }

.post-content ul, .post-content ol {
  padding-left: 1.5rem;
  margin-bottom: 1.4rem;
}

.post-content li { margin-bottom: 0.4rem; }

.post-content blockquote {
  border-left: 3px solid var(--accent);
  padding: 0.8rem 1.4rem;
  margin: 2rem 0;
  background: var(--surface);
  color: var(--text-dim);
  font-style: italic;
}

.post-content blockquote strong {
  color: var(--accent);
  font-style: normal;
}

.post-content code {
  font-family: var(--mono);
  font-size: 0.82rem;
  background: var(--code-bg);
  border: 1px solid var(--code-border);
  padding: 0.1em 0.4em;
  border-radius: 3px;
  color: #a8d8b9;
}

.post-content pre {
  background: var(--code-bg);
  border: 1px solid var(--code-border);
  border-radius: 6px;
  padding: 1.4rem 1.6rem;
  overflow-x: auto;
  margin: 1.5rem 0 2rem;
}

.post-content pre code {
  background: none;
  border: none;
  padding: 0;
  font-size: 0.8rem;
  line-height: 1.7;
  color: #cdd9e5;
}

/* math-style callout */
.math-block {
  background: var(--surface2);
  border: 1px solid var(--border);
  border-left: 3px solid var(--accent2);
  border-radius: 4px;
  padding: 1.2rem 1.6rem;
  margin: 1.8rem 0;
  font-family: var(--mono);
  font-size: 0.82rem;
  color: #cdd9e5;
  line-height: 1.9;
  overflow-x: auto;
  white-space: pre-wrap;
}

.math-block .label {
  font-size: 0.65rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent2);
  margin-bottom: 0.5rem;
}

/* info box */
.callout {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 1.2rem 1.6rem;
  margin: 2rem 0;
  font-size: 0.92rem;
}

.callout-title {
  font-family: var(--mono);
  font-size: 0.68rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 0.6rem;
}

/* figure / diagram placeholder */
.fig {
  margin: 2.5rem 0;
  background: var(--surface2);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 2rem;
  text-align: center;
}

.fig-caption {
  font-family: var(--mono);
  font-size: 0.7rem;
  color: var(--text-muted);
  margin-top: 0.8rem;
  letter-spacing: 0.04em;
  text-align: left;
}

/* series nav */
.series-nav {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 1.4rem 1.8rem;
  margin: 3rem 0;
}

.series-nav-title {
  font-family: var(--mono);
  font-size: 0.68rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-muted);
  margin-bottom: 0.8rem;
}

.series-nav ol {
  padding-left: 1.2rem;
  margin: 0;
}

.series-nav li {
  font-size: 0.88rem;
  color: var(--text-dim);
  margin-bottom: 0.3rem;
}

.series-nav li.active {
  color: var(--accent);
  font-weight: 600;
}

.series-nav a { color: var(--text-dim); text-decoration: none; }
.series-nav a:hover { color: var(--heading); }

/* ── FOOTER ── */
.site-footer {
  border-top: 1px solid var(--border);
  padding: 2rem;
  text-align: center;
  font-family: var(--mono);
  font-size: 0.7rem;
  color: var(--text-muted);
  letter-spacing: 0.06em;
}

/* ── SCROLLBAR ── */
::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: var(--bg); }
::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }

/* ── RESPONSIVE ── */
@media (max-width: 600px) {
  .post-item { grid-template-columns: 1fr; gap: 0.3rem 0; }
  .post-date-col { font-size: 0.65rem; }
  .site-header { padding: 1rem 1.2rem; }
  .home-hero, .post-list-section, .post-container { padding-left: 1.2rem; padding-right: 1.2rem; }
}