:root {
  --bg: #041b2d;
  --bg2: #063a5e;
  --card: #0a2c47;
  --ink: #eaf4fb;
  --muted: #9fc2da;
  --accent: #35c4f0;
  --line: rgba(255, 255, 255, 0.12);
}
* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  color: var(--ink);
  background: linear-gradient(160deg, var(--bg), var(--bg2));
  line-height: 1.65;
  min-height: 100vh;
}
.wrap { max-width: 760px; margin: 0 auto; padding: 32px 20px 80px; }
header.site { text-align: center; padding: 48px 20px 8px; }
header.site .logo {
  font-size: 30px; font-weight: 800; letter-spacing: 0.5px;
  display: inline-flex; align-items: center; gap: 10px;
}
header.site .tag { color: var(--muted); margin-top: 6px; }
nav { text-align: center; margin: 20px 0 8px; }
nav a {
  color: var(--accent); text-decoration: none; margin: 0 10px;
  font-weight: 600; font-size: 15px;
}
nav a:hover { text-decoration: underline; }
.card {
  background: var(--card); border: 1px solid var(--line);
  border-radius: 16px; padding: 28px 26px; margin-top: 24px;
}
h1 { font-size: 26px; margin: 0 0 4px; }
h2 { font-size: 19px; margin: 28px 0 8px; color: var(--accent); }
h3 { font-size: 16px; margin: 18px 0 6px; }
p, li { color: var(--ink); }
a { color: var(--accent); }
.muted { color: var(--muted); font-size: 14px; }
.lang-switch { text-align: right; margin-bottom: 8px; }
.lang-switch button {
  background: transparent; border: 1px solid var(--line); color: var(--muted);
  border-radius: 999px; padding: 4px 12px; margin-left: 6px; cursor: pointer;
  font-size: 13px; font-weight: 600;
}
.lang-switch button.active { background: var(--accent); color: #04222f; border-color: var(--accent); }
[data-lang] { display: none; }
[data-lang].show { display: block; }
footer { text-align: center; color: var(--muted); font-size: 13px; margin-top: 40px; }
code { background: rgba(255,255,255,0.08); padding: 2px 6px; border-radius: 6px; }