:root{
  --red:#C62828;
  --red-dark:#9E1B1B;
  --red-soft:#FDECEA;
  --navy:#1F2937;
  --gray:#6B7280;
  --line:#E5E7EB;
  --bg:#FAFAF8;
  --card:#FFFFFF;
  --amber:#B45309;
  --amber-soft:#FEF3E2;
  --blue:#185FA5;
  --blue-soft:#E6F1FB;
}
*{margin:0;padding:0;box-sizing:border-box}
html{scroll-behavior:smooth}
body{font-family:"PingFang SC","Microsoft YaHei","Noto Sans SC",-apple-system,"Segoe UI",sans-serif;color:var(--navy);background:var(--bg);line-height:1.7;font-size:16px}
a{color:var(--red);text-decoration:none}
a:hover{color:var(--red-dark)}
img{max-width:100%}
.container{max-width:1080px;margin:0 auto;padding:0 20px}

/* header */
.site-header{background:var(--card);border-bottom:1px solid var(--line);position:sticky;top:0;z-index:50}
.header-inner{display:flex;align-items:center;justify-content:space-between;height:64px}
.logo{display:flex;align-items:center;gap:10px;font-size:20px;font-weight:700;color:var(--navy)}
.logo-mark{width:34px;height:34px;border-radius:8px;background:var(--red);color:#fff;display:flex;align-items:center;justify-content:center;font-size:17px;font-weight:700}
.logo small{display:block;font-size:11px;font-weight:400;color:var(--gray);line-height:1.2}
.nav{display:flex;gap:4px}
.nav a{padding:8px 14px;border-radius:8px;color:var(--navy);font-size:15px}
.nav a:hover{background:var(--red-soft);color:var(--red)}
.nav a.on{background:var(--red);color:#fff}
.nav-toggle{display:none;background:none;border:1px solid var(--line);border-radius:8px;padding:6px 10px;font-size:14px;cursor:pointer}

/* hero */
.hero{background:linear-gradient(180deg,#FFF7F6,var(--bg));padding:52px 0 44px;border-bottom:1px solid var(--line)}
.hero h1{font-size:32px;line-height:1.35;margin-bottom:12px}
.hero .sub{color:var(--gray);font-size:17px;max-width:640px}
.hero .tags{margin-top:18px;display:flex;flex-wrap:wrap;gap:8px}
.tag{display:inline-block;padding:4px 12px;border-radius:999px;background:var(--red-soft);color:var(--red-dark);font-size:13px;border:1px solid #F3C1BC}

/* section */
.section{padding:40px 0}
.section h2{font-size:24px;margin-bottom:6px}
.section .sec-sub{color:var(--gray);margin-bottom:22px;font-size:15px}
.grid{display:grid;gap:16px}
.grid-2{grid-template-columns:1fr 1fr}
.grid-3{grid-template-columns:repeat(3,1fr)}
.card{background:var(--card);border:1px solid var(--line);border-radius:12px;padding:22px}
.card h3{font-size:17px;margin-bottom:8px;display:flex;align-items:center;gap:8px}
.card .idx{width:24px;height:24px;border-radius:50%;background:var(--red);color:#fff;font-size:13px;display:inline-flex;align-items:center;justify-content:center;flex-shrink:0}
.card p{color:var(--gray);font-size:14px}
.card a{font-weight:500}

/* callout */
.callout{border-radius:12px;padding:16px 18px;margin:18px 0;font-size:15px}
.callout p{margin:0}
.callout.info{background:var(--blue-soft);border:1px solid #B5D4F4;color:#0C447C}
.callout.warn{background:var(--amber-soft);border:1px solid #FAC775;color:#633806}
.callout.danger{background:var(--red-soft);border:1px solid #F7C1C1;color:#791F1F}
.callout b{display:block;margin-bottom:4px}

/* article */
.article{max-width:820px;margin:0 auto;background:var(--card);border:1px solid var(--line);border-radius:16px;padding:40px 48px;font-size:16.5px}
.article h1{font-size:30px;line-height:1.4;margin-bottom:10px}
.article .meta{color:var(--gray);font-size:13px;border-bottom:1px solid var(--line);padding-bottom:18px;margin-bottom:24px}
.article h2{font-size:22px;margin:34px 0 12px;padding-left:12px;border-left:4px solid var(--red)}
.article h3{font-size:18px;margin:24px 0 8px}
.article p{margin:10px 0}
.article ul,.article ol{margin:10px 0 10px 22px}
.article li{margin:6px 0}
.article table{width:100%;border-collapse:collapse;margin:16px 0;font-size:14.5px}
.article th{background:var(--red);color:#fff;padding:9px 10px;text-align:left;font-weight:500}
.article td{padding:8px 10px;border-bottom:1px solid var(--line)}
.article tr:nth-child(even) td{background:#FBF7F7}
.article .formula{background:var(--red-soft);border:1px solid #F3C1BC;border-radius:8px;padding:12px 16px;margin:14px 0;font-weight:500;color:var(--red-dark)}

/* FAQ */
.faq details{border:1px solid var(--line);border-radius:10px;margin:10px 0;background:var(--card)}
.faq summary{padding:14px 18px;cursor:pointer;font-weight:500;list-style:none;display:flex;justify-content:space-between;align-items:center}
.faq summary::after{content:"+";font-size:18px;color:var(--red);font-weight:700}
.faq details[open] summary::after{content:"−"}
.faq .faq-a{padding:0 18px 14px;color:var(--gray);font-size:15px}

/* steps */
.step{display:flex;gap:14px;margin:14px 0}
.step .num{width:30px;height:30px;border-radius:50%;background:var(--red);color:#fff;display:flex;align-items:center;justify-content:center;font-weight:700;flex-shrink:0;margin-top:2px}
.step b{display:block;margin-bottom:2px}

/* footer */
.site-footer{background:var(--navy);color:#C9D1DC;margin-top:48px;padding:36px 0 28px;font-size:13.5px}
.site-footer a{color:#E5E7EB}
.site-footer .disclaimer{background:rgba(255,255,255,.07);border-radius:10px;padding:14px 16px;margin-bottom:16px;line-height:1.8}
.site-footer .foot-links{margin-bottom:10px}
.site-footer .copy{color:#8B94A3}

/* table page */
.tbl-card{overflow-x:auto}
table.tbl{width:100%;border-collapse:collapse;font-size:14.5px;background:var(--card)}
table.tbl th{background:#F3F4F6;color:var(--navy);padding:10px;text-align:left;font-weight:500;border-bottom:2px solid var(--line)}
table.tbl td{padding:10px;border-bottom:1px solid var(--line)}
table.tbl tr.hot td{background:var(--red-soft)}

/* calculator */
.calc-grid{display:grid;grid-template-columns:1fr 1fr;gap:20px}
.field{margin-bottom:16px}
.field label{display:block;font-size:14px;color:var(--gray);margin-bottom:6px}
.field input,.field select{width:100%;padding:10px 12px;border:1px solid var(--line);border-radius:8px;font-size:16px;background:#fff;color:var(--navy)}
.field input:focus,.field select:focus{outline:2px solid var(--red);outline-offset:-1px;border-color:transparent}
.quick{display:flex;flex-wrap:wrap;gap:8px;margin-bottom:16px}
.quick button{padding:6px 12px;border-radius:999px;border:1px solid var(--line);background:#fff;font-size:13px;cursor:pointer;color:var(--navy)}
.quick button:hover{border-color:var(--red);color:var(--red)}
.quick button.on{background:var(--red);border-color:var(--red);color:#fff}
.result{background:var(--red-soft);border:1px solid #F3C1BC;border-radius:12px;padding:20px;text-align:center}
.result .big{font-size:34px;font-weight:700;color:var(--red)}
.result .lbl{font-size:13px;color:var(--red-dark);margin-top:2px}
.result .rows{display:grid;grid-template-columns:1fr 1fr 1fr;gap:10px;margin-top:16px}
.result .rows div{background:#fff;border-radius:8px;padding:10px 6px}
.result .rows .v{font-size:17px;font-weight:700;color:var(--navy)}
.result .rows .k{font-size:12px;color:var(--gray)}
.tip{font-size:13px;color:var(--gray);margin-top:12px}

/* responsive */
@media(max-width:820px){
  .grid-2,.grid-3,.calc-grid{grid-template-columns:1fr}
  .article{padding:26px 20px}
  .hero h1{font-size:26px}
  .nav{display:none;position:absolute;top:64px;left:0;right:0;background:#fff;flex-direction:column;padding:12px;border-bottom:1px solid var(--line)}
  .nav.show{display:flex}
  .nav-toggle{display:block}
}