:root {
  color-scheme: light;
  --ink: #18202a;
  --muted: #5f6975;
  --line: #dfe4ea;
  --paper: #ffffff;
  --wash: #f4f7fb;
  --accent: #2463eb;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  color: var(--ink);
  background: var(--wash);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  font-size: 16px;
  line-height: 1.7;
}

header {
  border-bottom: 1px solid var(--line);
  background: var(--paper);
}

.topbar,
main,
footer {
  width: min(900px, calc(100% - 40px));
  margin: 0 auto;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: 72px;
  gap: 24px;
}

.brand { font-weight: 750; letter-spacing: -0.02em; }

nav { display: flex; flex-wrap: wrap; gap: 18px; }

a { color: var(--accent); text-underline-offset: 3px; }
nav a { color: var(--muted); text-decoration: none; }
nav a:hover, nav a:focus-visible { color: var(--accent); }

main {
  margin-top: 40px;
  margin-bottom: 40px;
  padding: clamp(26px, 5vw, 56px);
  border: 1px solid var(--line);
  border-radius: 18px;
  background: var(--paper);
  box-shadow: 0 16px 45px rgba(24, 32, 42, 0.07);
}

h1 {
  margin: 0 0 8px;
  font-size: clamp(2rem, 5vw, 3.25rem);
  line-height: 1.15;
  letter-spacing: -0.04em;
}

h2 { margin-top: 2.1rem; font-size: 1.25rem; line-height: 1.35; }
h3 { margin-top: 1.5rem; font-size: 1.05rem; }
p, li { color: #303a46; }
.updated { margin: 0 0 28px; color: var(--muted); }
.notice {
  margin: 26px 0;
  padding: 18px 20px;
  border-left: 4px solid var(--accent);
  background: #eef4ff;
}
ul, ol { padding-left: 1.3rem; }
footer { padding: 0 0 42px; color: var(--muted); font-size: 14px; }

@media (max-width: 640px) {
  .topbar { align-items: flex-start; flex-direction: column; padding: 18px 0; gap: 10px; }
  main { width: min(100% - 24px, 900px); margin-top: 20px; padding: 24px 20px; border-radius: 14px; }
}