/* ─── Typography ─── */
@import url('https://fonts.googleapis.com/css2?family=Source+Serif+4:ital,opsz,wght@0,8..60,400;0,8..60,600;0,8..60,700;1,8..60,400;1,8..60,600&family=Inter:wght@400;500;600&display=swap');

:root {
  --color-bg: #faf9f6;
  --color-surface: #ffffff;
  --color-text: #2d2d2d;
  --color-heading: #1a1a1a;
  --color-muted: #6b7280;
  --color-link: #3d5a80;
  --color-link-hover: #263f5a;
  --color-border: #e5e5e5;
  --color-accent: #3d5a80;
  --color-tag-bg: #f0f0ed;

  --font-body: 'Source Serif 4', Georgia, 'Times New Roman', serif;
  --font-ui: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;

  --content-width: 680px;
  --wide-width: 900px;
}

/* ─── Reset & Base ─── */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

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

body {
  font-family: var(--font-body);
  line-height: 1.8;
  color: var(--color-text);
  background: var(--color-bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* ─── Navigation ─── */
nav {
  font-family: var(--font-ui);
  border-bottom: 1px solid var(--color-border);
  background: var(--color-bg);
  position: sticky;
  top: 0;
  z-index: 100;
}

nav .nav-inner {
  max-width: var(--wide-width);
  margin: 0 auto;
  padding: 1rem 1.5rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

nav .site-name {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--color-heading);
  text-decoration: none;
  letter-spacing: -0.02em;
}

nav .site-name:hover {
  color: var(--color-link);
}

nav .nav-links {
  display: flex;
  gap: 2rem;
  list-style: none;
}

nav .nav-links a {
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--color-muted);
  text-decoration: none;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  transition: color 0.2s;
}

nav .nav-links a:hover,
nav .nav-links a.active {
  color: var(--color-heading);
}

/* ─── Main Content Container ─── */
main {
  max-width: var(--content-width);
  margin: 0 auto;
  padding: 3rem 1.5rem;
}

/* ─── Page Header ─── */
.page-header {
  margin-bottom: 3rem;
  padding-bottom: 2rem;
  border-bottom: 1px solid var(--color-border);
}

.page-header h1 {
  font-family: var(--font-body);
  font-size: 2.4rem;
  font-weight: 700;
  color: var(--color-heading);
  line-height: 1.2;
  letter-spacing: -0.02em;
  margin-bottom: 0.5rem;
}

.page-header .subtitle {
  font-size: 1.1rem;
  color: var(--color-muted);
  font-style: italic;
}

/* ─── Blog Post List ─── */
.post-list {
  list-style: none;
}

.post-item {
  padding: 2rem 0;
  border-bottom: 1px solid var(--color-border);
}

.post-item:last-child {
  border-bottom: none;
}

.post-item a {
  text-decoration: none;
  color: inherit;
  display: block;
}

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

.post-date {
  font-family: var(--font-ui);
  font-size: 0.8rem;
  color: var(--color-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 0.4rem;
}

.post-title {
  font-family: var(--font-body);
  font-size: 1.5rem;
  font-weight: 600;
  color: var(--color-heading);
  line-height: 1.3;
  margin-bottom: 0.5rem;
  transition: color 0.2s;
}

.post-excerpt {
  font-size: 1rem;
  color: var(--color-muted);
  line-height: 1.6;
}

/* ─── Article Content (rendered markdown) ─── */
.article-header {
  margin-bottom: 2.5rem;
  text-align: center;
}

.article-header h1 {
  font-family: var(--font-body);
  font-size: 2.4rem;
  font-weight: 700;
  color: var(--color-heading);
  line-height: 1.2;
  letter-spacing: -0.02em;
  margin-bottom: 0.5rem;
}

.article-header .article-meta {
  font-family: var(--font-ui);
  font-size: 0.85rem;
  color: var(--color-muted);
}

.article-content h1 {
  font-size: 2rem;
  font-weight: 700;
  color: var(--color-heading);
  margin: 2.5rem 0 1rem;
  line-height: 1.2;
}

.article-content h2 {
  font-size: 1.6rem;
  font-weight: 600;
  color: var(--color-heading);
  margin: 2.5rem 0 0.8rem;
  line-height: 1.3;
}

.article-content h3 {
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--color-heading);
  margin: 2rem 0 0.6rem;
}

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

.article-content a {
  color: var(--color-link);
  text-decoration: underline;
  text-decoration-color: rgba(61, 90, 128, 0.3);
  text-underline-offset: 2px;
  transition: text-decoration-color 0.2s;
}

.article-content a:hover {
  text-decoration-color: var(--color-link);
}

.article-content blockquote {
  border-left: 3px solid var(--color-accent);
  padding-left: 1.2rem;
  margin: 1.5rem 0;
  color: var(--color-muted);
  font-style: italic;
}

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

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

.article-content img {
  max-width: 100%;
  height: auto;
  border-radius: 6px;
  margin: 1.5rem 0;
  display: block;
}

.article-content code {
  font-family: 'SF Mono', 'Fira Code', 'Consolas', monospace;
  font-size: 0.88em;
  background: var(--color-tag-bg);
  padding: 0.15em 0.4em;
  border-radius: 3px;
}

.article-content pre {
  background: #1a1a2e;
  color: #e0e0e0;
  padding: 1.2rem;
  border-radius: 6px;
  overflow-x: auto;
  margin: 1.5rem 0;
  line-height: 1.5;
}

.article-content pre code {
  background: none;
  padding: 0;
  font-size: 0.85rem;
}

.article-content hr {
  border: none;
  border-top: 1px solid var(--color-border);
  margin: 2.5rem 0;
}

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

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

/* ─── Profile / About Page ─── */
.profile-header {
  text-align: center;
  margin-bottom: 2.5rem;
}

.profile-header img {
  width: 160px;
  height: 160px;
  border-radius: 50%;
  object-fit: cover;
  margin-bottom: 1.2rem;
  border: 3px solid var(--color-border);
}

.profile-header h1 {
  font-family: var(--font-body);
  font-size: 2.4rem;
  font-weight: 700;
  color: var(--color-heading);
  margin-bottom: 0.3rem;
}

.profile-header .tagline {
  font-size: 1.05rem;
  color: var(--color-muted);
  font-style: italic;
}

/* Research image grid */
.article-content .research-img {
  margin: 2rem auto;
  max-width: 100%;
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.08);
}

.article-content .img-caption {
  text-align: center;
  font-family: var(--font-ui);
  font-size: 0.8rem;
  color: var(--color-muted);
  margin-top: -0.8rem;
  margin-bottom: 1.5rem;
}

/* ─── Back Link ─── */
.back-link {
  font-family: var(--font-ui);
  font-size: 0.85rem;
  color: var(--color-muted);
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  margin-bottom: 2rem;
  transition: color 0.2s;
}

.back-link:hover {
  color: var(--color-heading);
}

/* ─── Footer ─── */
footer {
  max-width: var(--wide-width);
  margin: 0 auto;
  padding: 2rem 1.5rem;
  text-align: center;
  font-family: var(--font-ui);
  font-size: 0.8rem;
  color: var(--color-muted);
  border-top: 1px solid var(--color-border);
}

/* ─── Loading State ─── */
.loading {
  text-align: center;
  padding: 3rem;
  color: var(--color-muted);
  font-style: italic;
}

/* ─── Empty State ─── */
.empty-state {
  text-align: center;
  padding: 3rem;
  color: var(--color-muted);
}

/* ─── Responsive ─── */
@media (max-width: 640px) {
  html {
    font-size: 16px;
  }

  nav .nav-inner {
    padding: 0.8rem 1rem;
  }

  nav .nav-links {
    gap: 1.2rem;
  }

  main {
    padding: 2rem 1rem;
  }

  .page-header h1,
  .article-header h1,
  .profile-header h1 {
    font-size: 1.8rem;
  }

  .post-title {
    font-size: 1.3rem;
  }

  .profile-header img {
    width: 120px;
    height: 120px;
  }
}