:root {
  --bg: #f7f6f2;
  --paper: #fffdf8;
  --text: #25231f;
  --muted: #6e685e;
  --line: #d9d3c8;
  --accent: #514537;
  --soft: #eee9df;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: ui-serif, Georgia, Cambria, "Times New Roman", Times, serif;
  line-height: 1.68;
  font-size: 18px;
}
a { color: #3f4f70; text-decoration-thickness: 1px; text-underline-offset: 3px; }
a:hover { color: #1f2d45; }
.site-header {
  border-bottom: 1px solid var(--line);
  background: rgba(255,253,248,.92);
  position: sticky;
  top: 0;
  z-index: 10;
  backdrop-filter: blur(8px);
}
.header-inner {
  max-width: 1120px;
  margin: 0 auto;
  padding: 16px 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}
.brand {
  font-family: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 17px;
  letter-spacing: .02em;
  font-weight: 650;
  color: var(--text);
  text-decoration: none;
}
.nav { display: flex; gap: 18px; flex-wrap: wrap; }
.nav a {
  font-family: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 14px;
  color: var(--muted);
  text-decoration: none;
}
.nav a:hover { color: var(--text); }
main {
  max-width: 880px;
  margin: 0 auto;
  padding: 56px 24px 72px;
}
.breadcrumbs {
  font-family: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 14px;
  color: var(--muted);
  margin-bottom: 32px;
}
.breadcrumbs a { color: var(--muted); text-decoration: none; }
h1 {
  font-size: clamp(38px, 5vw, 58px);
  line-height: 1.08;
  letter-spacing: -0.035em;
  font-weight: 520;
  margin: 0 0 22px;
}
h2 {
  font-size: 25px;
  line-height: 1.25;
  letter-spacing: -0.015em;
  margin-top: 46px;
  margin-bottom: 12px;
  font-weight: 560;
}
p { margin: 0 0 20px; }
.lead {
  font-size: 23px;
  line-height: 1.5;
  color: #36322b;
  margin-bottom: 34px;
}
.definition {
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  padding: 22px 0;
  margin: 0 0 34px;
}
.definition .label {
  display: block;
  font-family: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 12px;
  letter-spacing: .12em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 8px;
}
ul.concept-list {
  margin: 20px 0 0;
  padding-left: 24px;
}
ul.concept-list li { margin-bottom: 12px; }
.related {
  margin-top: 56px;
  padding-top: 24px;
  border-top: 1px solid var(--line);
}
.related h2 {
  margin-top: 0;
  font-size: 22px;
}
.related ul {
  padding-left: 22px;
  margin-top: 8px;
}
.lang-switch {
  margin: 36px 0 0;
  font-family: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 14px;
  color: var(--muted);
}
.layered-model {
  margin: 34px 0 40px;
  border: 1px solid var(--line);
  background: var(--paper);
}
.layered-model div {
  display: grid;
  grid-template-columns: 120px 1fr;
  gap: 18px;
  padding: 16px 20px;
  border-bottom: 1px solid var(--line);
}
.layered-model div:last-child { border-bottom: 0; }
.layered-model strong {
  font-family: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 13px;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: .08em;
}
.layered-model span { font-size: 18px; }
.site-footer {
  border-top: 1px solid var(--line);
  padding: 30px 24px 44px;
  color: var(--muted);
  font-family: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 14px;
}
.footer-inner {
  max-width: 1120px;
  margin: 0 auto;
}
.footer-inner p {
  margin: 0;
}
.footer-line {
  max-width: 100%;
}
@media (max-width: 720px) {
  body { font-size: 17px; }
  main { padding-top: 36px; }
  .lead { font-size: 20px; }
  .header-inner { align-items: flex-start; flex-direction: column; }
  .layered-model div { grid-template-columns: 1fr; gap: 4px; }
}