body {
  font-family: system-ui, -apple-system, Segoe UI, Roboto, sans-serif;
  max-width: 920px;
  margin: 0 auto;
  padding: 0 16px 64px;
  line-height: 1.65;
  color: #111;
}

a {
  color: #2563eb;
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

.topbar {
  position: sticky;
  top: 0;
  background: #ffffffcc;
  backdrop-filter: blur(6px);
  border-bottom: 1px solid #e5e7eb;
  z-index: 10;
  margin: 0 -16px 28px;
}

.topbar-inner {
  max-width: 920px;
  margin: 0 auto;
  padding: 12px 16px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.brand {
  font-weight: 700;
  letter-spacing: 0.2px;
  white-space: nowrap;
}

.menu {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  justify-content: flex-end;
  align-items: center;
}

.nav-link {
  font-weight: 600;
  padding: 6px 10px;
  border-radius: 8px;
}

.nav-link:hover {
  background: #eff6ff;
  text-decoration: none;
}

.nav-link.active {
  background: #2563eb;
  color: #fff;
}

.lang {
  display: flex;
  gap: 6px;
  align-items: center;
  margin-left: 6px;
}

.lang-btn {
  border: 1px solid #d1d5db;
  background: #fff;
  color: #111;
  padding: 6px 10px;
  border-radius: 8px;
  font-weight: 600;
  cursor: pointer;
}

.lang-btn:hover {
  background: #f3f4f6;
}

.lang-btn.active {
  background: #111;
  color: #fff;
  border-color: #111;
}

h1 {
  margin: 0 0 8px;
}

.meta {
  color: #555;
  margin: 0 0 18px;
  font-size: 14px;
}

.lead {
  margin: 0 0 22px;
}

nav.contents {
  margin: 18px 0 34px;
  padding: 16px;
  background: #f5f6f8;
  border-radius: 12px;
}

nav.contents ul {
  list-style: none;
  padding: 0;
  margin: 10px 0 0;
  display: grid;
  gap: 8px;
}

h2 {
  margin-top: 44px;
  scroll-margin-top: 88px;
}

footer {
  margin-top: 64px;
  padding-top: 18px;
  border-top: 1px solid #e5e7eb;
  font-size: 14px;
  color: #555;
}

@media (max-width: 520px) {
  .brand { display: none; }
  .menu { justify-content: flex-start; }
  h1 { font-size: 28px; }
  .lang { width: 100%; }
  .lang-btn { flex: 1; }
}