:root {
  --bg: #f4f6ff;
  --surface: #ffffff;
  --primary: #595cc6;
  --primary-dark: #313387;
  --text: #1a1d3a;
  --muted: #5e66b2;
  --border: #dce0ff;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
}

.header {
  background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
  color: #fff;
  padding: 32px 0 28px;
  box-shadow: 0 4px 20px rgba(49, 51, 135, 0.15);
}

.header-inner {
  max-width: 820px;
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 16px;
}

.brand {
  font-size: 18px;
  font-weight: 800;
  letter-spacing: 0.4px;
}

.lang-switch a {
  color: rgba(255, 255, 255, 0.85);
  margin-left: 12px;
  text-decoration: none;
  font-size: 13px;
  font-weight: 600;
  border: 1px solid rgba(255, 255, 255, 0.4);
  padding: 4px 10px;
  border-radius: 999px;
  transition: background 0.2s;
}

.lang-switch a.active,
.lang-switch a:hover {
  background: rgba(255, 255, 255, 0.18);
  color: #fff;
}

main {
  max-width: 820px;
  margin: -8px auto 48px;
  padding: 0 24px;
}

.card {
  background: var(--surface);
  border-radius: 20px;
  border: 1px solid var(--border);
  padding: 36px 36px 32px;
  box-shadow: 0 8px 24px rgba(45, 42, 117, 0.06);
}

h1 {
  margin: 0 0 8px;
  font-size: 28px;
  font-weight: 800;
  color: var(--primary-dark);
}

.meta {
  color: var(--muted);
  font-size: 13px;
  margin-bottom: 24px;
}

h2 {
  font-size: 18px;
  font-weight: 800;
  color: var(--primary-dark);
  margin: 28px 0 8px;
}

h3 {
  font-size: 15px;
  font-weight: 700;
  color: var(--text);
  margin: 18px 0 6px;
}

p, ul, ol {
  font-size: 15px;
  color: var(--text);
}

ul, ol {
  padding-left: 22px;
}

li {
  margin-bottom: 6px;
}

a {
  color: var(--primary);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

.toc {
  background: #f6f7ff;
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 14px 18px;
  margin: 16px 0 24px;
}

.toc strong {
  display: block;
  margin-bottom: 4px;
  color: var(--primary-dark);
  font-size: 13px;
  letter-spacing: 0.4px;
  text-transform: uppercase;
}

.toc ol {
  margin: 0;
  padding-left: 20px;
}

.toc a {
  font-size: 14px;
}

footer {
  text-align: center;
  color: var(--muted);
  font-size: 12px;
  padding: 16px 24px 32px;
}

@media (max-width: 600px) {
  .card { padding: 24px 20px; }
  h1 { font-size: 22px; }
  h2 { font-size: 16px; }
}