@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&display=swap');

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

:root {
  --bg: #ffffff;
  --bg-secondary: #FAFAFB;
  --text: #1A1D21;
  --text-secondary: #68707C;
  --text-tertiary: #8F99A8;
  --border: #EDEFF3;
  --border-strong: #D0D5DD;
  --stroke-subtle: #E4E7EC;
  --black-800: #505967;
  --primary: #1A1D21;
  --primary-hover: #2C3038;
}

html {
  font-family: 'Inter', system-ui, -apple-system, sans-serif;
  font-size: 16px;
  line-height: 1.5;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  background: var(--bg);
}

body > footer {
  margin-top: auto;
  flex-shrink: 0;
}

.container {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 24px;
  width: 100%;
}

/* Grid Background */
.grid-bg {
  background-image:
    linear-gradient(to right, var(--border) 1px, transparent 1px),
    linear-gradient(to bottom, var(--border) 1px, transparent 1px);
  background-size: 8.33% 8.33%;
}

/* Header / Sticky Nav */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--bg);
  border-bottom: 1px solid var(--border);
}

/* Navigation */
nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 20px 0;
}

.nav-name {
  font-size: 18px;
  font-weight: 600;
  color: var(--text);
  text-decoration: none;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 24px;
  list-style: none;
}

.nav-links a {
  text-decoration: none;
  color: var(--text-secondary);
  font-size: 14px;
  font-weight: 500;
  transition: color 0.2s;
}

.nav-links a:hover {
  color: var(--text);
}

/* Hero */
.hero {
  position: relative;
  padding: 100px 0 80px;
  text-align: center;
  overflow: hidden;
}

.hero h1 {
  font-size: clamp(40px, 6vw, 72px);
  font-weight: 600;
  line-height: 1.08;
  letter-spacing: -0.03em;
}

.hero .title {
  font-size: 18px;
  color: var(--text-tertiary);
  font-weight: 500;
  margin-top: 12px;
  letter-spacing: 0.02em;
}

.hero .abstract {
  font-size: 16px;
  color: var(--text-secondary);
  margin-top: 28px;
  max-width: 680px;
  margin-left: auto;
  margin-right: auto;
  font-weight: 400;
  line-height: 1.7;
}

.hero .abstract + .abstract {
  margin-top: 16px;
}

.hero-avatar {
  width: 80px;
  height: 80px;
  border-radius: 50%;
  object-fit: cover;
  margin-bottom: 24px;
  border: 2px solid var(--border);
}

.hero-grid {
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(to right, var(--border) 1px, transparent 1px),
    linear-gradient(to bottom, var(--border) 1px, transparent 1px);
  background-size: 8.33% 8.33%;
  pointer-events: none;
  mask-image: radial-gradient(ellipse 70% 60% at 50% 40%, black 20%, transparent 70%);
  -webkit-mask-image: radial-gradient(ellipse 70% 60% at 50% 40%, black 20%, transparent 70%);
}

/* Page Header (for blog pages) */
.page-header {
  position: relative;
  padding: 80px 0 50px;
  text-align: center;
  overflow: hidden;
}

.page-header h1 {
  font-size: clamp(32px, 4vw, 48px);
  font-weight: 600;
  line-height: 1.15;
  letter-spacing: -0.02em;
}

.page-header .meta {
  font-size: 14px;
  color: var(--text-tertiary);
  margin-top: 12px;
  font-weight: 500;
}

.page-header .grid-bg-inner {
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(to right, var(--border) 1px, transparent 1px),
    linear-gradient(to bottom, var(--border) 1px, transparent 1px);
  background-size: 8.33% 8.33%;
  pointer-events: none;
  mask-image: radial-gradient(ellipse 70% 60% at 50% 40%, black 20%, transparent 70%);
  -webkit-mask-image: radial-gradient(ellipse 70% 60% at 50% 40%, black 20%, transparent 70%);
}

/* Divider */
.divider {
  height: 1px;
  background: var(--border);
  width: 100%;
}

.divider-dashed {
  height: 1px;
  width: 100%;
  background: repeating-linear-gradient(
    to right,
    var(--stroke-subtle) 0,
    var(--stroke-subtle) 4px,
    transparent 4px,
    transparent 10px
  );
}

/* Section common */
.section {
  position: relative;
}

.section-header {
  padding: 60px 0 0;
}

.section-header .overline {
  font-size: 13px;
  font-weight: 600;
  color: var(--text-tertiary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.section-header h2 {
  font-size: 28px;
  font-weight: 600;
  margin-top: 4px;
}

.section-border {
  border-left: 1px solid var(--border);
  border-right: 1px solid var(--border);
}

/* Feature Grid */
.feature-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0;
}

.feature-card {
  padding: 36px 28px;
  border-right: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
  transition: background 0.2s;
}

.feature-card:hover {
  background: var(--bg-secondary);
}

.feature-card:nth-child(3n) {
  border-right: none;
}

.feature-icon {
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 10px;
  background: var(--bg-secondary);
  margin-bottom: 14px;
  font-size: 18px;
  font-weight: 600;
  color: var(--text-secondary);
}

.feature-card h3 {
  font-size: 16px;
  font-weight: 600;
  margin-bottom: 6px;
}

.feature-card .meta {
  font-size: 13px;
  color: var(--text-tertiary);
  margin-bottom: 8px;
}

.feature-card p {
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.6;
}

.feature-card a {
  color: var(--text);
  text-decoration: none;
  font-weight: 500;
}

.feature-card a:hover {
  text-decoration: underline;
}

.feature-card .tags {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin-top: 10px;
}

.feature-card .tags a {
  display: inline-block;
  font-size: 12px;
  font-weight: 500;
  color: var(--text-tertiary);
  border: 1px solid var(--border-strong);
  padding: 2px 10px;
  border-radius: 999px;
  text-decoration: none;
  transition: all 0.2s;
}

.feature-card .tags a:hover {
  color: var(--text);
  border-color: var(--text-tertiary);
  text-decoration: none;
}

/* Tag list (interests) */
.tag-list {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  justify-content: center;
  padding: 40px 20px 48px;
}

.tag-list a {
  display: inline-block;
  font-size: 14px;
  font-weight: 500;
  color: var(--text-secondary);
  border: 1px solid var(--border-strong);
  padding: 8px 20px;
  border-radius: 999px;
  text-decoration: none;
  transition: all 0.2s;
}

.tag-list a:hover {
  color: var(--text);
  border-color: var(--text-tertiary);
  background: var(--bg-secondary);
}

/* Blog Article Content */
.article-content {
  max-width: 720px;
  margin: 0 auto;
  padding: 48px 0 64px;
  counter-reset: section;
}

.article-content h2 {
  counter-reset: subsection;
  font-size: 22px;
  font-weight: 600;
  margin-top: 40px;
  margin-bottom: 12px;
  line-height: 1.3;
}

.article-content h2::before {
  counter-increment: section;
  content: counter(section) ". ";
}

.article-content h3 {
  counter-reset: subsubsection;
  font-size: 18px;
  font-weight: 600;
  margin-top: 32px;
  margin-bottom: 10px;
  line-height: 1.3;
}

.article-content h3::before {
  counter-increment: subsection;
  content: counter(section) "." counter(subsection) ". ";
}

.article-content h4 {
  counter-reset: subsubsubsection;
  font-size: 16px;
  font-weight: 600;
  margin-top: 24px;
  margin-bottom: 8px;
  line-height: 1.3;
}

.article-content h4::before {
  counter-increment: subsubsection;
  content: counter(section) "." counter(subsection) "." counter(subsubsection) ". ";
}

.article-content h5 {
  font-size: 15px;
  font-weight: 600;
  margin-top: 20px;
  margin-bottom: 6px;
  line-height: 1.3;
}

.article-content h5::before {
  counter-increment: subsubsubsection;
  content: counter(section) "." counter(subsection) "." counter(subsubsection) "." counter(subsubsubsection) ". ";
}

.article-content p {
  font-size: 15px;
  line-height: 1.7;
  color: var(--text);
  margin-bottom: 16px;
}

.article-content ul,
.article-content ol {
  padding-left: 24px;
  margin-bottom: 16px;
}

.article-content li {
  font-size: 15px;
  line-height: 1.7;
  color: var(--text);
  margin: 6px 0;
}

.article-content a {
  color: var(--text);
  text-decoration: underline;
  text-underline-offset: 2px;
}

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

.article-content strong {
  font-weight: 600;
}

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

.article-content figure {
  margin: 32px auto;
  text-align: center;
}

.article-content figure img {
  max-width: 100%;
  height: auto;
  display: block;
  margin: 0 auto;
  border-radius: 8px;
  border: 1px solid var(--border);
  cursor: zoom-in;
}

.article-content figcaption {
  font-size: 13px;
  color: var(--text-tertiary);
  margin-top: 8px;
  font-style: italic;
}

.article-content .figure-row {
  display: flex;
  gap: 24px;
  justify-content: center;
  align-items: flex-start;
  flex-wrap: wrap;
  margin: 32px 0;
}

.article-content .figure-row figure {
  flex: 1 1 0;
  min-width: 240px;
  margin: 0;
}

.article-content table {
  margin: 32px auto;
  border-collapse: collapse;
  font-size: 14px;
  width: 100%;
}

.article-content table th,
.article-content table td {
  border: 1px solid var(--border-strong);
  padding: 10px 16px;
  text-align: center;
}

.article-content table th {
  background: var(--bg-secondary);
  font-weight: 600;
}

.article-content table td {
  background: var(--bg);
}

.article-content blockquote {
  border-left: 3px solid var(--border-strong);
  padding-left: 20px;
  margin: 24px 0;
  color: var(--text-secondary);
  font-style: italic;
}

.article-content code {
  font-family: 'SF Mono', 'Fira Code', monospace;
  font-size: 13px;
  background: var(--bg-secondary);
  padding: 2px 6px;
  border-radius: 4px;
  border: 1px solid var(--border);
}

.article-content .page-tags-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 24px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
}

.article-content .page-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.article-content .page-tags a,
.article-content .article-links a {
  display: inline-block;
  font-size: 12px;
  font-weight: 500;
  color: var(--text-tertiary);
  border: 1px solid var(--border-strong);
  padding: 4px 14px;
  border-radius: 999px;
  text-decoration: none;
  transition: all 0.2s;
}

.article-content .page-tags a:hover,
.article-content .article-links a:hover {
  color: var(--text);
  border-color: var(--text-tertiary);
}

.article-content .article-links {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.article-content .article-subtitle {
  font-size: 16px;
  font-style: italic;
  color: var(--text-secondary);
  line-height: 1.7;
  margin: 28px 0 32px;
  padding: 16px 20px;
  background: var(--bg-secondary);
  border-left: 3px solid var(--border-strong);
  border-radius: 0 8px 8px 0;
}

/* TOC */
.toc {
  margin: 32px 0 40px;
  padding: 20px 24px;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 8px;
}

.toc-label {
  font-size: 12px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-tertiary);
  display: block;
  margin-bottom: 12px;
}

.toc ol {
  list-style: none;
  margin: 0;
  padding: 0;
}

.toc ol ol {
  padding-left: 20px;
}

.toc li {
  font-size: 14px;
  line-height: 1.8;
}

.toc > ol > li {
  font-weight: 500;
}

.toc a {
  color: var(--text);
  text-decoration: underline;
  text-underline-offset: 2px;
  text-decoration-color: var(--border-strong);
}

.toc a:hover {
  color: var(--text-secondary);
}

/* Lightbox */
.lightbox {
  display: none;
  position: fixed;
  z-index: 1000;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  background: rgba(0,0,0,0.85);
  justify-content: center;
  align-items: center;
  cursor: zoom-out;
}

.lightbox.active {
  display: flex;
}

.lightbox img {
  max-width: 90vw;
  max-height: 90vh;
  object-fit: contain;
  border-radius: 4px;
}

/* Blog List (tag pages) */
.blog-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.blog-list li {
  display: flex;
  align-items: baseline;
  flex-wrap: wrap;
  gap: 4px;
  padding: 12px 0;
  border-bottom: 1px solid var(--border);
}

.blog-list li:last-child {
  border-bottom: none;
}

.blog-list li a {
  font-size: 15px;
  font-weight: 500;
  color: var(--text);
  text-decoration: none;
}

.blog-list li a:hover {
  text-decoration: underline;
}

.blog-list li .date {
  font-size: 13px;
  color: var(--text-tertiary);
}

/* Button */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 8px 20px;
  border-radius: 10px;
  font-size: 14px;
  font-weight: 500;
  text-decoration: none;
  cursor: pointer;
  border: 1px solid var(--border-strong);
  color: var(--text-secondary);
  transition: all 0.2s;
}

.btn:hover {
  color: var(--text);
  border-color: var(--text-tertiary);
  background: var(--bg-secondary);
}

/* Footer */
footer {
  background: var(--primary);
  color: #fff;
  padding: 60px 0 40px;
  margin-top: 0;
  border-top: none;
}

footer .divider {
  background: rgba(255,255,255,0.1);
  margin-bottom: 40px;
}

.footer-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.footer-name {
  font-size: 16px;
  font-weight: 600;
}

.footer-tagline {
  font-size: 13px;
  color: rgba(255,255,255,0.4);
  margin-top: 2px;
}

.footer-social {
  display: flex;
  gap: 20px;
  align-items: center;
}

.footer-social a {
  color: rgba(255,255,255,0.5);
  text-decoration: none;
  font-size: 14px;
  font-weight: 500;
  transition: color 0.2s;
}

.footer-social a:hover {
  color: #fff;
}

.footer-bottom {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 40px;
  padding-top: 20px;
  border-top: 1px solid rgba(255,255,255,0.1);
  font-size: 13px;
  color: rgba(255,255,255,0.35);
}

/* Utilities */
.border-x { border-left: 1px solid var(--border); border-right: 1px solid var(--border); }
.border-t { border-top: 1px solid var(--border); }
.border-b { border-bottom: 1px solid var(--border); }

/* Responsive */
@media (max-width: 1024px) {
  .feature-grid { grid-template-columns: repeat(2, 1fr); }
  .feature-card:nth-child(3n) { border-right: 1px solid var(--border); }
  .feature-card:nth-child(2n) { border-right: none; }
}

@media (max-width: 768px) {
  .container { padding: 0 16px; }
  .hero { padding: 60px 0 50px; }
  .page-header { padding: 50px 0 36px; }
  .feature-grid { grid-template-columns: 1fr; }
  .feature-card:nth-child(n) { border-right: none; }
  .footer-inner { flex-direction: column; gap: 20px; text-align: center; }
  .footer-bottom { flex-direction: column; gap: 8px; text-align: center; }
  nav { flex-direction: column; gap: 12px; }
  .article-content { padding: 32px 0 48px; }
  .article-content .figure-row { flex-direction: column; }
}