:root{
    --navy:#122A46; --navy-deep:#0B1D33;
    --gold:#B8862B; --gold-light:#D9AE5C;
    --paper:#F6F3EC; --paper-line:#E4DDCB;
    --ink:#1D2430; --ink-soft:#5B6472;
    --green:#3F6B4A; --red:#9B3B34;
  }
  *{box-sizing:border-box;}
  body{margin:0;background:var(--paper);color:var(--ink);font-family:'Inter',sans-serif;line-height:1.6;}
  a{color:var(--navy);}

  .band{background:var(--navy-deep);color:#EFE7D6;border-bottom:3px solid var(--gold);position:sticky;top:0;z-index:30;}
  .band-inner{max-width:1180px;margin:0 auto;padding:20px 24px 0;display:flex;align-items:center;justify-content:space-between;gap:20px;flex-wrap:wrap;}
  .eyebrow{font-family:'JetBrains Mono',monospace;font-size:11px;letter-spacing:.14em;text-transform:uppercase;color:var(--gold-light);margin:0 0 6px;}
  .eyebrow a{color:var(--gold-light);text-decoration:underline;text-underline-offset:2px;}
  .eyebrow a:hover{color:#F1ECDD;}
  .brandbar{background:var(--gold);color:var(--navy-deep);}
  .brandbar-inner{max-width:1180px;margin:0 auto;padding:8px 24px;font-size:12.5px;font-weight:600;display:flex;align-items:center;justify-content:center;gap:6px;text-align:center;flex-wrap:wrap;}
  .brandbar a{color:var(--navy-deep);text-decoration:underline;text-underline-offset:2px;}
  .brandbar a:hover{color:#fff;}
  .author-box{
    background:#fff;border:1px solid var(--paper-line);border-left:3px solid var(--gold);
    padding:20px 22px;margin:44px 0 10px;border-radius:4px;display:flex;align-items:center;gap:16px;flex-wrap:wrap;
  }
  .author-box .txt{flex:1;min-width:220px;font-size:13.5px;color:var(--ink-soft);}
  .author-box .txt b{color:var(--navy);}
  .author-box a.cta{
    font-family:'JetBrains Mono',monospace;font-size:12px;font-weight:600;color:#fff;background:var(--navy);
    padding:10px 18px;border-radius:3px;text-decoration:none;white-space:nowrap;
  }
  .author-box a.cta:hover{background:var(--gold);color:var(--navy-deep);}
  .intro-lede{font-size:14px;color:var(--ink-soft);max-width:78ch;margin:0 0 30px;line-height:1.7;}
  .intro-lede a{color:var(--navy);font-weight:600;}
  h1{font-family:'Source Serif 4',serif;font-weight:700;font-size:clamp(18px,2.4vw,24px);margin:0;color:#F7F1E3;}
  .search-wrap{position:relative;min-width:240px;flex:1;max-width:400px;}
  #globalSearch{width:100%;padding:10px 14px 10px 36px;border:1px solid #2A4364;border-radius:4px;background:#0F2237;color:#F1ECDD;font-family:'Inter',sans-serif;font-size:13.5px;}
  #globalSearch::placeholder{color:#7C8AA0;}
  #globalSearch:focus{outline:none;border-color:var(--gold);}
  .search-icon{position:absolute;left:12px;top:50%;transform:translateY(-50%);color:#7C8AA0;font-size:13px;pointer-events:none;}

  .sitenav{max-width:1180px;margin:0 auto;padding:14px 24px 0;display:flex;gap:6px;flex-wrap:wrap;}
  .sitenav a{
    font-family:'JetBrains Mono',monospace;font-size:11.5px;letter-spacing:.03em;
    background:#0F2237;color:#B9BFC9;border:1px solid #2A4364;border-bottom:none;
    padding:9px 14px;border-radius:4px 4px 0 0;text-decoration:none;white-space:nowrap;
  }
  .sitenav a.active{background:var(--paper);color:var(--navy);border-color:var(--paper-line);font-weight:600;}
  .sitenav a:hover:not(.active){color:#EFE7D6;}

  .modcards{display:grid;grid-template-columns:repeat(auto-fit,minmax(260px,1fr));gap:16px;margin:28px 0 44px;}
  .modcard{
    display:block;background:#fff;border:1px solid var(--paper-line);border-left:3px solid var(--gold);
    padding:20px 22px;border-radius:4px;text-decoration:none;transition:box-shadow .15s, transform .15s;
  }
  .modcard:hover{box-shadow:0 4px 18px rgba(18,42,70,.10);transform:translateY(-1px);}
  .modcard .tag{font-family:'JetBrains Mono',monospace;font-size:10.5px;text-transform:uppercase;letter-spacing:.06em;color:var(--gold);margin-bottom:8px;}
  .modcard h3{font-family:'Source Serif 4',serif;font-weight:600;font-size:16.5px;color:var(--navy);margin:0 0 8px;}
  .modcard p{font-size:13px;color:var(--ink-soft);margin:0;line-height:1.55;}

  .layout{max-width:1180px;margin:0 auto;padding:30px 24px 90px;}

  /* module sections now render as always-visible content on their own dedicated page */

  .quickref{display:grid;grid-template-columns:repeat(auto-fit,minmax(210px,1fr));gap:14px;margin-bottom:38px;}
  .qcard{background:#fff;border:1px solid var(--paper-line);border-left:3px solid var(--gold);padding:14px 16px;border-radius:2px;}
  .qcard .k{font-family:'JetBrains Mono',monospace;font-size:10.5px;text-transform:uppercase;letter-spacing:.06em;color:var(--ink-soft);margin-bottom:5px;}
  .qcard .v{font-size:14px;font-weight:600;color:var(--navy);line-height:1.4;}

  .chuong-head{
    font-family:'Source Serif 4',serif;font-weight:700;font-size:19px;color:var(--navy);
    padding:22px 0 10px;border-bottom:2px solid var(--navy);margin-bottom:18px;margin-top:44px;
    display:flex;align-items:baseline;gap:10px;
  }
  .chuong-head:first-of-type{margin-top:0;}
  .chuong-head .n{font-family:'JetBrains Mono',monospace;color:var(--gold);font-size:14px;}

  .item{background:#fff;border:1px solid var(--paper-line);border-radius:4px;margin-bottom:14px;overflow:hidden;}
  .item-head{display:flex;align-items:center;justify-content:space-between;gap:12px;padding:14px 18px;cursor:pointer;user-select:none;}
  .item-head:hover{background:var(--paper);}
  .item-title{display:flex;align-items:baseline;gap:10px;flex-wrap:wrap;}
  .item-num{font-family:'JetBrains Mono',monospace;font-size:12px;color:var(--gold);font-weight:600;white-space:nowrap;}
  .item-name{font-family:'Source Serif 4',serif;font-weight:600;font-size:15.5px;color:var(--navy);}
  .caret{font-size:11px;color:var(--ink-soft);transition:transform .15s;flex-shrink:0;}
  .item.open .caret{transform:rotate(90deg);}
  .item-body{display:none;padding:0 18px 20px;font-size:13.8px;color:var(--ink);}
  .item.open .item-body{display:block;}
  .item-body p{margin:0 0 10px;}
  .item-body ul,.item-body ol{margin:0 0 10px;padding-left:22px;}
  .item-body li{margin-bottom:6px;}
  .item-body b{color:var(--navy);}
  .item-body table{width:100%;border-collapse:collapse;margin:10px 0;font-size:13px;}
  .item-body th{background:var(--navy);color:#EFE7D6;padding:7px 10px;text-align:left;font-size:12px;}
  .item-body td{padding:7px 10px;border-top:1px solid var(--paper-line);}
  .item-body tr:nth-child(even) td{background:var(--paper);}
  .core{position:relative;}
  .core::after{content:"CỐT LÕI";display:inline-block;font-family:'JetBrains Mono',monospace;font-size:9px;letter-spacing:.05em;color:var(--gold);border:1px solid var(--gold);border-radius:2px;padding:1px 5px;margin-left:8px;vertical-align:middle;}

  mark{background:var(--gold-light);color:var(--navy-deep);border-radius:2px;padding:0 1px;}
  .hidden{display:none !important;}
  .no-results{padding:40px 20px;text-align:center;color:var(--ink-soft);font-size:14px;display:none;}
  .modtag{font-family:'JetBrains Mono',monospace;font-size:9.5px;color:#fff;background:var(--navy);padding:2px 7px;border-radius:2px;letter-spacing:.04em;}

  .calc{background:#fff;border:1px solid var(--paper-line);border-left:4px solid var(--gold);padding:22px 24px;margin-bottom:18px;}
  .formula{font-family:'JetBrains Mono',monospace;font-size:16px;font-weight:600;color:var(--navy);background:var(--paper);padding:12px 16px;text-align:center;margin-bottom:18px;border:1px dashed var(--paper-line);}
  .grid{display:grid;grid-template-columns:1fr 1fr;gap:14px 20px;}
  @media(max-width:600px){.grid{grid-template-columns:1fr;}}
  label{display:block;font-size:12px;font-weight:600;color:var(--ink-soft);margin-bottom:5px;text-transform:uppercase;letter-spacing:.03em;}
  select,input[type=number]{width:100%;padding:8px 9px;border:1px solid var(--paper-line);background:var(--paper);font-family:'Inter',sans-serif;font-size:13.5px;color:var(--ink);}
  select:focus,input[type=number]:focus{outline:none;border-color:var(--gold);}
  .result{margin-top:18px;padding:16px 18px;background:var(--navy);color:#F7F1E3;display:flex;align-items:center;justify-content:space-between;flex-wrap:wrap;gap:8px;}
  .result .label{font-size:12px;color:#B9BFC9;font-weight:600;text-transform:uppercase;letter-spacing:.05em;}
  .result .value{font-family:'JetBrains Mono',monospace;font-size:24px;font-weight:600;color:var(--gold-light);}
  .breakdown{font-family:'JetBrains Mono',monospace;font-size:11.5px;color:var(--ink-soft);margin-top:8px;}

  .convtable-toggle{display:inline-block;margin-top:6px;font-family:'JetBrains Mono',monospace;font-size:11px;color:var(--gold);cursor:pointer;border:1px solid var(--gold);padding:5px 10px;border-radius:3px;}
  .convtable{display:none;margin-top:12px;}
  .convtable.open{display:block;}
  .convtable table{font-size:12px;}

  .src-note{font-size:11.5px;color:var(--ink-soft);background:#fff;border:1px dashed var(--paper-line);padding:10px 14px;border-radius:4px;margin-bottom:26px;}

  footer{max-width:1180px;margin:0 auto;padding:0 24px 60px;font-size:11.5px;color:var(--ink-soft);border-top:1px solid var(--paper-line);padding-top:18px;}
  ::-webkit-scrollbar{width:8px;}
  ::-webkit-scrollbar-thumb{background:var(--paper-line);border-radius:4px;}