:root{
    --bg:#F4F2EC; --card:#FFFFFF; --ink:#1B1D1A; --dim:#5E6359; --line:#D8D5CA; --accent:#9A3B2B;
    box-sizing:border-box;
    padding-top:env(safe-area-inset-top,0px);
    padding-bottom:env(safe-area-inset-bottom,0px);
  }
  @media (prefers-color-scheme:dark){
    :root:not([data-theme="light"]){--bg:#15171A;--card:#1D2024;--ink:#ECEAE3;--dim:#9A9D94;--line:#30343A;--accent:#E08A6D;}
  }
  :root[data-theme="dark"]{--bg:#15171A;--card:#1D2024;--ink:#ECEAE3;--dim:#9A9D94;--line:#30343A;--accent:#E08A6D;}
  *{box-sizing:inherit;margin:0;padding:0}
  html{scroll-padding-top:env(safe-area-inset-top,0px);}
  body{background:var(--bg);color:var(--ink);font-family:"Noto Sans TC","PingFang TC","Microsoft JhengHei",sans-serif;line-height:1.75;}
  .wrap{max-width:860px;margin:0 auto;padding:56px 24px 80px;}
  h1,h2,.serif{font-family:"Noto Serif TC","Songti TC",serif;font-weight:600;}
  h1{font-size:clamp(1.9rem,5vw,2.8rem);line-height:1.3;margin-bottom:18px;}
  .lead{color:var(--dim);font-size:1.08rem;max-width:56ch;}
  h2{font-size:1.4rem;margin:64px 0 20px;}
  .note{font-size:.85rem;color:var(--dim);margin-top:12px;}

  /* spectrum */
  .tabs{display:grid;grid-template-columns:repeat(4,1fr);gap:0;border:1px solid var(--line);border-radius:10px;overflow:hidden;margin-bottom:0;}
  .tab{background:var(--card);border:none;border-right:1px solid var(--line);padding:16px 8px;cursor:pointer;color:var(--dim);font:inherit;font-size:.95rem;text-align:center;}
  .tab:last-child{border-right:none}
  .tab small{display:block;font-size:.75rem;margin-bottom:2px;opacity:.7}
  .tab[aria-selected="true"]{background:var(--accent);color:#fff;}
  .bar{height:4px;background:var(--line);margin:14px 0 0;border-radius:2px;overflow:hidden}
  .bar i{display:block;height:100%;width:25%;background:var(--accent);transition:width .35s ease}
  .panel{background:var(--card);border:1px solid var(--line);border-radius:10px;padding:28px;margin-top:14px;min-height:230px;}
  .panel h3{font-size:1.2rem;margin-bottom:10px}
  .panel p{color:var(--dim);margin-bottom:12px}
  .panel b{color:var(--ink)}
  @media (max-width:560px){.tab{font-size:.8rem;padding:12px 4px}}

  /* nuclear + factors */
  .grid{display:grid;grid-template-columns:repeat(2,1fr);gap:16px;}
  @media (max-width:640px){.grid{grid-template-columns:1fr}}
  .card{background:var(--card);border:1px solid var(--line);border-radius:10px;padding:22px;}
  .card h3{font-size:1.02rem;margin-bottom:8px;color:var(--accent)}
  .card p{color:var(--dim);font-size:.95rem}

  /* accordion */
  details{border-top:1px solid var(--line);padding:16px 0;}
  details:last-of-type{border-bottom:1px solid var(--line)}
  summary{cursor:pointer;font-weight:500;list-style:none;display:flex;justify-content:space-between;}
  summary::after{content:"+";color:var(--accent);font-size:1.3rem;line-height:1}
  details[open] summary::after{content:"−"}
  details p{color:var(--dim);margin-top:10px;max-width:60ch}

  .toggle{position:fixed;top:calc(12px + env(safe-area-inset-top,0px));right:16px;background:var(--card);border:1px solid var(--line);color:var(--ink);border-radius:999px;padding:6px 14px;font:inherit;font-size:.82rem;cursor:pointer;}
  footer{margin-top:64px;color:var(--dim);font-size:.85rem;border-top:1px solid var(--line);padding-top:20px}