:root {
  --bg: #f6f8fb;
  --card: #ffffff;
  --text: #17202a;
  --muted: #5f6b7a;
  --primary: #0f6cbd;
  --border: #d9e2ec;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
  line-height: 1.6;
  color: var(--text);
  background: var(--bg);
}
header {
  background: var(--card);
  border-bottom: 1px solid var(--border);
  padding: 24px 20px;
}
.header-inner, main, footer {
  max-width: 920px;
  margin: 0 auto;
}
.brand {
  font-size: 22px;
  font-weight: 700;
  margin: 0 0 4px;
}
.subtitle { color: var(--muted); margin: 0; }
nav { margin-top: 14px; }
nav a {
  display: inline-block;
  margin: 6px 12px 0 0;
  color: var(--primary);
  text-decoration: none;
}
main {
  background: var(--card);
  margin-top: 24px;
  margin-bottom: 24px;
  padding: 34px;
  border: 1px solid var(--border);
  border-radius: 12px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.04);
}
h1 { line-height: 1.2; margin-top: 0; }
h2 { margin-top: 30px; border-top: 1px solid var(--border); padding-top: 22px; }
h3 { margin-top: 22px; }
p, li { font-size: 16px; }
ul { padding-left: 24px; }
.notice {
  border-left: 4px solid var(--primary);
  padding: 12px 16px;
  background: #eef6ff;
  margin: 20px 0;
}
.placeholder {
  background: #fff7e6;
  border: 1px solid #ffd591;
  padding: 2px 6px;
  border-radius: 4px;
}
footer {
  color: var(--muted);
  font-size: 14px;
  padding: 0 20px 30px;
}
@media (max-width: 640px) {
  main { padding: 22px; margin: 16px 12px; }
  header { padding: 20px 12px; }
}