*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
:root {
  --red: #E8271A;
  --text: #111;
  --text-2: #444;
  --text-3: #888;
  --line: #E5E5E5;
  --bg: #fff;
  --bg-soft: #F7F7F6;
}
body {
  font-family: Geist, system-ui, sans-serif;
  background: var(--bg);
  color: var(--text);
  -webkit-font-smoothing: antialiased;
}
.nav {
  position: sticky; top: 0; z-index: 20;
  height: 64px; display: flex; align-items: center; justify-content: space-between;
  padding: 0 40px;
  background: rgba(255,255,255,.92);
  backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--line);
}
.nav-logo { font-size: 22px; font-weight: 800; color: var(--text); text-decoration: none; letter-spacing: -.5px; }
.nav-logo b { color: var(--red); }
.nav-back { font-size: 14px; color: var(--text-2); text-decoration: none; font-weight: 500; }
.nav-back:hover { color: var(--text); }
.wrap {
  max-width: 1100px;
  margin: 0 auto;
  padding: 48px 40px 80px;
  display: grid;
  grid-template-columns: 240px 1fr;
  gap: 56px;
  align-items: start;
}
.side { position: sticky; top: 88px; }
.side h3 {
  font-size: 11px; font-weight: 700; letter-spacing: .12em;
  text-transform: uppercase; color: var(--text-3); margin-bottom: 14px;
}
.side a {
  display: block; padding: 10px 0;
  font-size: 14px; color: var(--text-2); text-decoration: none;
  border-bottom: 1px solid var(--line); font-weight: 500;
}
.side a:hover { color: var(--text); }
.side a.active { color: var(--red); font-weight: 700; }
.article h1 {
  font-size: clamp(28px, 4vw, 40px);
  font-weight: 800; letter-spacing: -1.2px; line-height: 1.15;
  margin-bottom: 10px;
}
.updated { font-size: 13px; color: var(--text-3); margin-bottom: 28px; }
.article h2 {
  font-size: 18px; font-weight: 800; letter-spacing: -.3px;
  margin: 32px 0 10px;
}
.article p, .article li {
  font-size: 15px; line-height: 1.75; color: var(--text-2); font-weight: 400;
}
.article p { margin-bottom: 12px; }
.article ul { padding-left: 20px; margin-bottom: 14px; }
.article li { margin-bottom: 6px; }
.article a { color: var(--red); }
.note {
  background: var(--bg-soft);
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 16px 18px;
  margin: 20px 0;
  font-size: 14px;
  color: var(--text-2);
  line-height: 1.65;
}
footer {
  border-top: 1px solid var(--line);
  padding: 22px 40px;
  font-size: 13px; color: var(--text-3);
  display: flex; justify-content: space-between; gap: 12px; flex-wrap: wrap;
}
footer a { color: var(--text-3); text-decoration: none; }
footer a:hover { color: var(--text); }
@media (max-width: 800px) {
  .nav { padding: 0 20px; height: 56px; }
  .wrap { grid-template-columns: 1fr; padding: 32px 20px 64px; gap: 28px; }
  .side { position: static; }
}