:root {
  --bg: #ffffff;
  --surface: #f5f7fa;
  --text: #14161a;
  --muted: #5b6472;
  --accent: #2e7df6;
  --border: #e3e8ef;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #101216;
    --surface: #191d24;
    --text: #f2f4f7;
    --muted: #9aa4b2;
    --accent: #5c9bff;
    --border: #262c36;
  }
}
* { box-sizing: border-box; }
body {
  margin: 0;
  padding: 40px 20px 80px;
  background: var(--bg);
  color: var(--text);
  font: 16px/1.65 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}
main { max-width: 720px; margin: 0 auto; }
header { display: flex; align-items: center; gap: 14px; margin-bottom: 8px; }
.mark {
  width: 44px; height: 44px; border-radius: 11px; flex: none;
  background: linear-gradient(135deg, #2e7df6, #143f96);
  position: relative;
}
.mark::before, .mark::after {
  content: ""; position: absolute; border: 2px solid #fff; border-radius: 2px;
  top: 50%; left: 50%; transform: translate(-50%, -50%);
}
.mark::before { width: 18px; height: 32px; }
.mark::after { width: 31px; height: 17px; border-color: #bfdaff; }
h1 { font-size: 26px; margin: 0; letter-spacing: -0.01em; }
h2 { font-size: 19px; margin: 34px 0 10px; letter-spacing: -0.01em; }
h3 { font-size: 16px; margin: 22px 0 6px; }
p, li { color: var(--text); }
.muted { color: var(--muted); font-size: 14px; }
ul { padding-left: 20px; }
li { margin: 5px 0; }
a { color: var(--accent); }
.card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: 14px; padding: 18px 20px; margin: 18px 0;
}
hr { border: 0; border-top: 1px solid var(--border); margin: 44px 0; }
nav { margin: 22px 0 0; font-size: 14px; }
nav a { margin-right: 16px; }
footer { margin-top: 48px; color: var(--muted); font-size: 13px; }