:root{
  --bg:#f7f9fb;
  --fg:#1e2a36;
  --muted:#6b7a8a;
  --accent:#3b82f6;
  --line:#e2e8f0;
}
*{box-sizing:border-box}
body{
  margin:0;
  font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Ubuntu,sans-serif;
  background:var(--bg);
  color:var(--fg);
  line-height:1.6;
}
.container{max-width:820px;margin:0 auto;padding:0 20px}
header{
  background:#fff;
  border-bottom:1px solid var(--line);
  position:sticky;top:0;z-index:10;
}
header .container{display:flex;justify-content:space-between;align-items:center;padding-top:14px;padding-bottom:14px}
.logo{font-weight:700;text-decoration:none;color:var(--fg);font-size:18px}
nav a{margin-left:18px;text-decoration:none;color:var(--muted);font-size:15px}
nav a:hover{color:var(--accent)}
main{padding:40px 20px 60px}
.hero h1{font-size:32px;margin:0 0 10px}
.hero p{color:var(--muted);font-size:17px}
h2{margin-top:36px;font-size:22px}
table.aqi{width:100%;border-collapse:collapse;margin-top:12px;background:#fff;border-radius:8px;overflow:hidden}
table.aqi th,table.aqi td{padding:10px 14px;border-bottom:1px solid var(--line);text-align:left;font-size:15px}
table.aqi th{background:#eef4fb;font-weight:600}
ul{padding-left:20px}
ul li{margin-bottom:6px}
a{color:var(--accent)}
footer{border-top:1px solid var(--line);padding:20px 0;background:#fff;font-size:14px;color:var(--muted)}
footer .muted{font-size:13px;color:#9aa7b4}
@media(max-width:600px){
  .hero h1{font-size:24px}
  nav a{margin-left:12px;font-size:14px}
}