:root {
  --bg: #eceff1;
  --surface: #ffffff;
  --surface-muted: #f8f9fa;
  --text: #1f2933;
  --muted: #5f6c76;
  --line: #d9dee3;
  --line-strong: #c7cfd6;
  --link: #1d4f91;
  --link-hover: #12345f;
  --shadow: 0 1px 2px rgba(15, 23, 42, 0.05), 0 10px 24px rgba(15, 23, 42, 0.05);
}

html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.5;
}

a { color: var(--link); }
a:hover { color: var(--link-hover); }

.site-shell { min-height: 100vh; }
.site-header {
  background: #f4f6f8;
  border-bottom: 1px solid var(--line-strong);
}
.header-inner {
  max-width: 980px;
  margin: 0 auto;
  padding: 24px 24px 18px;
}
.site-kicker {
  margin: 0 0 8px;
  font-size: 0.78rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
}
.site-header h1 {
  margin: 0;
  font-size: clamp(1.7rem, 3vw, 2.3rem);
  line-height: 1.15;
}

.tab-nav {
  max-width: 980px;
  margin: 0 auto;
  padding: 0 24px 16px;
}
.tab-nav ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}
.tab-nav a {
  display: block;
  text-decoration: none;
  padding: 8px 12px;
  border: 1px solid var(--line-strong);
  background: #fff;
  color: var(--text);
  box-shadow: 0 1px 0 rgba(15,23,42,0.03);
}
.tab-nav a:hover {
  background: var(--surface-muted);
  color: var(--link-hover);
}
.tab-nav a.is-active {
  border-color: #9eaab3;
  background: #eef2f5;
  font-weight: 600;
}

.content {
  max-width: 980px;
  margin: 0 auto;
  padding: 22px 24px 28px;
}
.content-panel { display: none; }
.content-panel.is-active { display: block; }
.content-card {
  background: var(--surface);
  border: 1px solid var(--line-strong);
  box-shadow: var(--shadow);
}
.content-card__body {
  padding: 24px 28px;
}

h2, h3 {
  line-height: 1.25;
  color: #18232d;
}
h2 {
  margin: 0 0 12px;
  font-size: 1.45rem;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--line);
}
h3 {
  margin: 14px 0 6px;
  font-size: 1rem;
  color: #243442;
}
p {
  margin: 6px 0 8px;
}

.site-footer {
  border-top: 1px solid var(--line-strong);
  background: #f6f7f9;
  margin-top: 28px;
}
.footer-inner {
  max-width: 980px;
  margin: 0 auto;
  padding: 14px 24px 22px;
}
.footer-block + .footer-block {
  margin-top: 12px;
}
.site-footer--small,
.site-footer--small p,
.site-footer--small a {
  font-size: 0.78rem;
  color: #98a2ab;
}
.site-footer h3 {
  margin: 0 0 4px;
  font-size: 0.9rem;
  color: #7d8790;
}

@media (max-width: 640px) {
  .header-inner,
  .tab-nav,
  .content,
  .footer-inner {
    padding-left: 16px;
    padding-right: 16px;
  }
  .content-card__body {
    padding: 18px;
  }
  .tab-nav ul {
    gap: 8px;
  }
  .tab-nav a {
    width: 100%;
    box-sizing: border-box;
  }
}