:root {
  --bg: #f4f4f1;
  --paper: #fcfcf9;
  --paper-strong: #ffffff;
  --text: #191919;
  --muted: #50504b;
  --line: rgba(17, 17, 17, 0.12);
  --line-strong: rgba(17, 17, 17, 0.22);
  --accent: #c84f3d;
  --accent-soft: rgba(200, 79, 61, 0.12);
  --shadow: 0 18px 50px rgba(0, 0, 0, 0.05);
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
  --font-serif: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
  --radius: 24px;
}

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

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-width: 320px;
  font-family: var(--font-sans);
  font-size: 1.0625rem;
  color: var(--text);
  background: linear-gradient(180deg, #f8f8f4 0%, var(--bg) 100%);
  line-height: 1.72;
  letter-spacing: 0.002em;
}

img {
  display: block;
  max-width: 100%;
}

a {
  color: inherit;
  text-decoration: none;
}

a:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 4px;
}

.container {
  width: min(1120px, calc(100% - 32px));
  margin: 0 auto;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  backdrop-filter: blur(12px);
  background: rgba(244, 244, 241, 0.82);
  border-bottom: 1px solid var(--line);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  min-height: 72px;
}

.brand {
  display: inline-flex;
  flex-direction: column;
  gap: 2px;
}

.brand-mark {
  font-family: var(--font-serif);
  font-size: 1.56rem;
  font-weight: 700;
  letter-spacing: -0.015em;
}

.brand-subtitle {
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--muted);
}

.site-nav {
  display: flex;
  align-items: center;
  gap: 20px;
  font-size: 1rem;
}

.site-nav a,
.primary-link,
.secondary-link,
.note-list a,
.note-card h3 a {
  transition: color 0.18s ease, opacity 0.18s ease, border-color 0.18s ease, background-color 0.18s ease;
}

.site-nav a:hover,
.site-nav a:focus-visible,
.note-list a:hover,
.note-list a:focus-visible,
.note-card h3 a:hover,
.note-card h3 a:focus-visible {
  color: var(--accent);
}

.hero {
  padding: 40px 0 24px;
}

.paper {
  position: relative;
  background: linear-gradient(180deg, var(--paper-strong) 0%, var(--paper) 100%);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

.hero-paper {
  padding: 48px 56px 44px 92px;
}

.eyebrow,
.section-label,
.note-topline {
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--muted);
}

.hero h1,
.section-head h2,
.about-paper h2,
.note-card h3 {
  font-family: var(--font-serif);
  letter-spacing: -0.018em;
}

.hero h1 {
  max-width: 760px;
  margin: 14px 0 18px;
  font-size: clamp(2.5rem, 4.6vw, 4.4rem);
  line-height: 1.04;
}

.hero-copy {
  max-width: 620px;
  margin: 0;
  font-size: 1.14rem;
  color: var(--muted);
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
  margin-top: 28px;
}

.primary-link,
.secondary-link {
  display: inline-flex;
  align-items: center;
  min-height: 46px;
  padding: 0 16px;
  border-radius: 999px;
  border: 1px solid var(--line-strong);
  font-size: 0.95rem;
}

.primary-link {
  background: var(--text);
  color: #ffffff;
  border-color: var(--text);
}

.primary-link:hover,
.primary-link:focus-visible {
  background: #2d2d2d;
  border-color: #2d2d2d;
}

.secondary-link {
  background: var(--accent-soft);
  border-color: rgba(200, 79, 61, 0.28);
  color: var(--accent);
}

.secondary-link:hover,
.secondary-link:focus-visible {
  background: rgba(200, 79, 61, 0.18);
}

.hero-notes {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin: 30px 0 0;
  padding: 0;
  list-style: none;
}

.hero-notes li {
  padding: 7px 12px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.72);
  font-size: 0.92rem;
}

.section-intro {
  padding-top: 28px;
}

.popular-section {
  padding-top: 28px;
}

.popular-paper {
  padding: 30px 32px 30px 78px;
}

.section-head {
  display: flex;
  flex-direction: column;
  gap: 10px;
  max-width: 700px;
}

.section-head h2,
.about-paper h2 {
  margin: 0;
  font-size: clamp(2rem, 3.6vw, 2.9rem);
  line-height: 1.12;
}

.notes-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 24px;
  padding: 28px 0 0;
}

.popular-list {
  margin: 22px 0 0;
  padding: 0;
  list-style: none;
  border-top: 1px solid var(--line);
}

.popular-list li {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 14px 0;
  border-bottom: 1px solid var(--line);
}

.popular-list a {
  flex: 1;
  transition: color 0.18s ease;
}

.popular-list a:hover,
.popular-list a:focus-visible {
  color: var(--accent);
}

.popular-list span {
  flex-shrink: 0;
  color: var(--muted);
  font-size: 0.9rem;
}

.popular-more {
  margin-top: 14px;
}

.popular-more summary {
  width: fit-content;
  cursor: pointer;
  color: var(--accent);
  font-weight: 600;
  list-style: none;
}

.popular-more summary::-webkit-details-marker {
  display: none;
}

.popular-more summary::after {
  content: " +";
}

.popular-more[open] summary::after {
  content: " -";
}

.popular-list-more {
  margin-top: 14px;
}

.note-card {
  padding: 30px 32px 28px 78px;
}

.note-card h3 {
  margin: 12px 0 10px;
  font-size: 1.92rem;
  line-height: 1.14;
}

.note-card p,
.about-paper p {
  margin: 0;
  color: var(--muted);
}

.note-list {
  margin: 22px 0 0;
  padding: 0;
  list-style: none;
  border-top: 1px solid var(--line);
}

.note-list li {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
  padding: 14px 0;
  border-bottom: 1px solid var(--line);
}

.note-list li::before {
  content: "•";
  margin-right: 10px;
  color: var(--line-strong);
}

.note-list a {
  flex: 1;
}

.note-list-item-accent {
  color: var(--accent);
}

.note-list-item-accent::before {
  color: var(--accent);
}

.note-flag {
  flex-shrink: 0;
  padding: 4px 8px;
  border-radius: 999px;
  background: var(--accent);
  color: #ffffff;
  font-size: 0.74rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.about-section {
  padding: 24px 0 72px;
}

.about-paper {
  padding: 32px 40px 32px 78px;
  display: grid;
  gap: 16px;
}

.article-shell {
  padding: 32px 0 72px;
}

.article-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 280px;
  gap: 24px;
  align-items: start;
}

.article-paper {
  padding: 36px 42px 40px 86px;
}

.article-aside {
  padding: 28px 28px 30px 32px;
  position: sticky;
  top: 96px;
}

.article-meta {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
}

.article-backlink {
  color: var(--muted);
  font-size: 0.95rem;
  transition: color 0.18s ease;
}

.article-backlink:hover,
.article-backlink:focus-visible {
  color: var(--accent);
}

.article-header {
  padding: 16px 0 24px;
  border-bottom: 1px solid var(--line);
}

.article-header h1 {
  margin: 0;
  font-family: var(--font-serif);
  font-size: clamp(2.2rem, 4.4vw, 3.7rem);
  line-height: 1.08;
  letter-spacing: -0.02em;
}

.article-lead {
  margin: 18px 0 0;
  max-width: 760px;
  font-size: 1.16rem;
  line-height: 1.74;
  color: var(--muted);
}

.article-body {
  padding-top: 24px;
}

.article-body p,
.article-body li,
.article-body figcaption {
  font-size: 1.1rem;
  line-height: 1.8;
}

.article-body a {
  color: var(--accent);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 0.16em;
}

.article-body a:hover,
.article-body a:focus-visible {
  color: var(--text);
}

.article-body p,
.article-body ol,
.article-body ul,
.article-callout,
.article-figure,
.code-block,
.article-body table,
.article-body blockquote,
.article-body iframe {
  margin: 0 0 18px;
}

.article-section {
  padding: 0 0 28px;
}

.article-section h2 {
  margin: 0 0 12px;
  font-family: var(--font-serif);
  font-size: clamp(1.6rem, 2.8vw, 2.05rem);
  line-height: 1.18;
  letter-spacing: -0.015em;
}

.article-body h3,
.article-body h4 {
  margin: 28px 0 10px;
  font-family: var(--font-serif);
  line-height: 1.2;
  letter-spacing: -0.012em;
}

.article-body h3 {
  font-size: clamp(1.42rem, 2.4vw, 1.75rem);
}

.article-body h4 {
  font-size: 1.22rem;
}

.article-section-last {
  padding-bottom: 0;
}

.article-note {
  color: var(--muted);
  font-size: 0.95rem;
}

.article-steps {
  margin-left: 18px;
  padding-left: 0;
}

.article-body ul,
.article-body ol {
  padding-left: 1.3rem;
}

.article-steps li + li {
  margin-top: 10px;
}

.article-body li + li {
  margin-top: 0.55rem;
}

.code-block {
  padding: 16px 18px;
  border: 1px solid var(--line);
  border-radius: 18px;
  background: rgba(17, 17, 17, 0.03);
  overflow-x: auto;
}

.code-block code,
.article-lead code,
.article-body p code,
.article-body li code {
  font-family: "SFMono-Regular", "Menlo", "Monaco", "Courier New", monospace;
  font-size: 0.95em;
}

.article-lead code,
.article-body p code,
.article-body li code {
  padding: 0.15em 0.38em;
  border-radius: 6px;
  background: rgba(17, 17, 17, 0.06);
}

.article-figure {
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: 22px;
  background: rgba(255, 255, 255, 0.7);
}

.article-figure img {
  width: 100%;
  height: auto;
}

.article-figure figcaption {
  padding: 14px 16px 16px;
  color: var(--muted);
  border-top: 1px solid var(--line);
}

.article-callout {
  padding: 16px 18px;
  border-radius: 18px;
  border: 1px solid rgba(200, 79, 61, 0.24);
  background: var(--accent-soft);
}

.article-body .notification,
.article-body .note {
  padding: 16px 18px;
  border-radius: 18px;
  border: 1px solid var(--line);
  background: rgba(17, 17, 17, 0.03);
}

.article-body blockquote {
  padding: 14px 18px;
  border-left: 3px solid var(--accent);
  background: rgba(200, 79, 61, 0.08);
  color: var(--muted);
}

.article-body kbd,
.article-body .key,
.article-body .path {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 2rem;
  padding: 0.15rem 0.55rem;
  border: 1px solid var(--line-strong);
  border-bottom-width: 2px;
  border-radius: 10px;
  background: #fff;
  box-shadow: 0 1px 0 rgba(17, 17, 17, 0.06);
  font-family: "SFMono-Regular", "Menlo", "Monaco", "Courier New", monospace;
  font-size: 0.88em;
}

.article-body .keys {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 18px;
}

.article-body .key-plus {
  color: var(--muted);
  font-weight: 600;
}

.article-body table {
  width: 100%;
  border-collapse: collapse;
  border-top: 1px solid var(--line);
}

.article-body th,
.article-body td {
  padding: 12px 10px;
  border-bottom: 1px solid var(--line);
  text-align: left;
  vertical-align: top;
}

.article-body th {
  font-weight: 700;
}

.article-body iframe {
  width: 100%;
  max-width: 100%;
  border: 0;
  border-radius: 18px;
  min-height: 315px;
}

.article-aside h2 {
  margin: 12px 0 16px;
  font-family: var(--font-serif);
  font-size: 1.7rem;
  line-height: 1.05;
  letter-spacing: -0.03em;
}

.aside-links {
  margin: 0;
  padding: 0;
  list-style: none;
  border-top: 1px solid var(--line);
}

.aside-links li {
  border-bottom: 1px solid var(--line);
}

.aside-links a {
  display: block;
  padding: 14px 0;
  transition: color 0.18s ease;
}

.aside-links a:hover,
.aside-links a:focus-visible {
  color: var(--accent);
}

.site-footer {
  border-top: 1px solid var(--line);
  padding: 24px 0 44px;
}

.footer-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}

.footer-copy {
  color: var(--muted);
  font-size: 0.98rem;
}

.footer-copy p {
  margin: 0;
}

.social-links {
  display: flex;
  align-items: center;
  gap: 10px;
}

.social-links a {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: rgba(255, 255, 255, 0.76);
  transition: border-color 0.18s ease, background-color 0.18s ease, transform 0.18s ease;
}

.social-links a:hover,
.social-links a:focus-visible {
  border-color: var(--text);
  background: #ffffff;
  transform: translateY(-1px);
}

.social-links img {
  width: 18px;
  height: 18px;
  object-fit: contain;
  filter: grayscale(1) contrast(1.2);
}

@media (max-width: 960px) {
  .notes-grid {
    grid-template-columns: 1fr;
  }

  .article-layout {
    grid-template-columns: 1fr;
  }

  .article-aside {
    position: static;
  }

  .footer-inner {
    flex-direction: column;
    align-items: flex-start;
  }
}

@media (max-width: 720px) {
  .header-inner {
    min-height: 64px;
  }

  .site-nav {
    gap: 14px;
    font-size: 0.96rem;
  }

  .hero {
    padding-top: 24px;
  }

  .hero-paper,
  .popular-paper,
  .note-card,
  .about-paper,
  .article-paper,
  .article-aside {
    padding-left: 28px;
    padding-right: 24px;
    background: linear-gradient(180deg, var(--paper-strong) 0%, var(--paper) 100%);
  }

  .note-card h3 {
    font-size: 1.62rem;
  }

  .article-header h1 {
    font-size: clamp(2.05rem, 8vw, 3rem);
  }

  .note-list li {
    align-items: flex-start;
  }

  .popular-list li {
    align-items: flex-start;
    flex-direction: column;
  }
}

@media (max-width: 540px) {
  .container {
    width: min(100% - 20px, 1120px);
  }

  .header-inner {
    flex-direction: column;
    align-items: flex-start;
    justify-content: center;
    padding: 14px 0;
  }

  .hero-actions {
    flex-direction: column;
    align-items: stretch;
  }

  .primary-link,
  .secondary-link {
    justify-content: center;
  }

  .note-list li {
    flex-wrap: wrap;
  }

  .social-links {
    flex-wrap: wrap;
  }
}