/* Bố cục: thanh mục lục trái (khung bản vẽ) + trang tính giữa + cột hình/kết quả phải.
   Màu kế thừa sổ tay Excel: xanh mực 1F4E79, ô vàng = nhập, ô xanh lá = kết quả chính. */
:root {
  --ink: #1f4e79;          /* xanh mực – tiêu đề, khung */
  --ink-soft: #3d6a95;
  --paper: #f5f7f9;        /* nền giấy, ngả xanh lạnh */
  --sheet: #ffffff;
  --line: #d5dde6;
  --line-strong: #a9b7c6;
  --text: #17222d;
  --muted: #5b6876;
  --in-bg: #fff2cc;        /* ô nhập */
  --in-line: #e5c86a;
  --res-bg: #e2efda;       /* ô kết quả chính */
  --res-line: #a9cf94;
  --ok: #2f7d32; --ok-bg: #e3f2e1;
  --bad: #b3261e; --bad-bg: #fbe4e2;
  --warn: #9a6400; --warn-bg: #fdf0d5;
  --focus: #2b7de9;
  --f-display: "Barlow Condensed", "Arial Narrow", system-ui, sans-serif;
  --f-body: "Be Vietnam Pro", system-ui, -apple-system, "Segoe UI", sans-serif;
  --f-mono: "IBM Plex Mono", ui-monospace, Consolas, monospace;
  --side-w: 300px;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --ink: #8fb8e3; --ink-soft: #6c98c6; --paper: #10161d; --sheet: #161e27; --line: #26323f; --line-strong: #3a4a5b;
    --text: #e3e9ef; --muted: #93a1b0; --in-bg: #3a3218; --in-line: #7a6526; --res-bg: #1d3320; --res-line: #3d6b40;
    --ok: #7cd283; --ok-bg: #1b3a1e; --bad: #ff8a80; --bad-bg: #42201d; --warn: #f2c063; --warn-bg: #3a2f14; --focus: #6aa8ff;
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --ink: #8fb8e3; --ink-soft: #6c98c6; --paper: #10161d; --sheet: #161e27; --line: #26323f; --line-strong: #3a4a5b;
  --text: #e3e9ef; --muted: #93a1b0; --in-bg: #3a3218; --in-line: #7a6526; --res-bg: #1d3320; --res-line: #3d6b40;
  --ok: #7cd283; --ok-bg: #1b3a1e; --bad: #ff8a80; --bad-bg: #42201d; --warn: #f2c063; --warn-bg: #3a2f14; --focus: #6aa8ff;
  color-scheme: dark;
}
* { box-sizing: border-box; }
[hidden] { display: none !important; }
html, body { height: 100%; }
body { margin: 0; background: var(--paper); color: var(--text); font: 14px/1.5 var(--f-body); }
a { color: var(--ink); }
button, input, select { font: inherit; color: inherit; }
:focus-visible { outline: 2px solid var(--focus); outline-offset: 2px; }

/* ---------- khung */
.app { display: grid; grid-template-columns: var(--side-w) minmax(0, 1fr); min-height: 100%; }
.side { position: sticky; top: env(safe-area-inset-top, 0px); height: 100vh; overflow: auto; background: var(--sheet); border-right: 1px solid var(--line); display: flex; flex-direction: column; }
.brand { padding: 18px 18px 12px; border-bottom: 2px solid var(--ink); text-decoration: none; display: block; }
.brand b { display: block; text-wrap: balance; font: 600 21px/1.05 var(--f-display); letter-spacing: .01em; color: var(--ink); text-transform: uppercase; }
.brand span { font-size: 12px; color: var(--muted); }
.search { padding: 12px 14px; border-bottom: 1px solid var(--line); position: sticky; top: 0; background: var(--sheet); z-index: 2; }
.search input { width: 100%; padding: 8px 10px; border: 1px solid var(--line-strong); border-radius: 4px; background: var(--paper); }
.toc { padding: 4px 0 24px; }
.toc .part { margin-top: 10px; }
.toc .part > h3 { margin: 0; padding: 8px 16px 4px; font: 600 13px/1.2 var(--f-display); letter-spacing: .08em; text-transform: uppercase; color: var(--ink); }
.toc .grp { padding: 6px 16px 2px; font-size: 11px; font-weight: 600; color: var(--muted); text-transform: uppercase; letter-spacing: .06em; }
.toc a.it { display: grid; grid-template-columns: 42px 1fr; gap: 6px; padding: 4px 16px; text-decoration: none; color: var(--text); font-size: 13px; line-height: 1.35; border-left: 3px solid transparent; }
.toc a.it:hover { background: var(--paper); }
.toc a.it.on { background: var(--res-bg); border-left-color: var(--ink); }
.toc a.it code { font: 500 11px/1.6 var(--f-mono); color: var(--ink-soft); }
.toc .none { padding: 16px; color: var(--muted); }

.main { min-width: 0; padding-inline: 28px; padding-block: 22px 60px; }
.topbar { display: none; }

/* ---------- trang chủ */
.home { max-width: 1100px; }
.home h1 { font: 600 44px/1 var(--f-display); text-transform: uppercase; color: var(--ink); margin: 6px 0 10px; text-wrap: balance; }
.home .lead { max-width: 68ch; color: var(--muted); margin: 0 0 6px; }
.home .note { max-width: 68ch; font-size: 13px; padding: 10px 12px; border-left: 3px solid var(--in-line); background: var(--in-bg); margin: 14px 0 26px; }
.stats { display: flex; flex-wrap: wrap; gap: 28px; margin: 18px 0 8px; }
.stats div b { display: block; font: 600 34px/1 var(--f-display); color: var(--ink); font-variant-numeric: tabular-nums; }
.stats div span { font-size: 12px; color: var(--muted); }
.hpart { margin-top: 30px; }
.hpart h2 { font: 600 24px/1.1 var(--f-display); text-transform: uppercase; color: var(--ink); margin: 0 0 4px; border-bottom: 2px solid var(--ink); padding-bottom: 6px; }
.hpart > p { color: var(--muted); margin: 6px 0 12px; max-width: 80ch; }
.hgrp h4 { margin: 16px 0 8px; font-size: 12px; text-transform: uppercase; letter-spacing: .06em; color: var(--muted); }
.cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 8px; }
.card { display: grid; grid-template-columns: auto 1fr; gap: 2px 10px; padding: 10px 12px; background: var(--sheet); border: 1px solid var(--line); border-radius: 4px; text-decoration: none; color: var(--text); }
.card:hover { border-color: var(--ink-soft); }
.card code { grid-row: span 2; font: 600 12px/1.5 var(--f-mono); color: var(--ink); }
.card b { font-weight: 600; font-size: 13.5px; line-height: 1.3; }
.card span { font-size: 12px; color: var(--muted); line-height: 1.35; }
.hnote { font-size: 12.5px; color: var(--muted); margin-top: 10px; }
.srcs { margin-top: 36px; font-size: 13px; }
.srcs dt { font-weight: 600; margin-top: 8px; }
.srcs dd { margin: 2px 0 0; color: var(--muted); }

/* ---------- trang tính */
.calc { max-width: 1320px; }
.tblock { display: grid; grid-template-columns: auto 1fr; border: 2px solid var(--ink); background: var(--sheet); }
.tblock .code { display: grid; place-items: center; padding: 10px 18px; background: var(--ink); color: var(--sheet); font: 600 30px/1 var(--f-display); letter-spacing: .02em; }
.tblock .ttl { padding: 10px 16px; min-width: 0; }
.tblock h1 { margin: 0; font: 600 28px/1.1 var(--f-display); text-transform: uppercase; color: var(--ink); text-wrap: balance; }
.tblock .std { font-size: 12.5px; color: var(--muted); margin-top: 2px; }
.tblock .desc { grid-column: 1 / -1; border-top: 1px solid var(--line); padding: 8px 16px; font-size: 13.5px; }
.toolbar { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; margin: 12px 0; }
.btn { border: 1px solid var(--line-strong); background: var(--sheet); padding: 6px 12px; border-radius: 4px; cursor: pointer; font-size: 13px; }
.btn:hover { border-color: var(--ink); color: var(--ink); }
.btn.on { background: var(--ink); color: var(--sheet); border-color: var(--ink); }
.legend { margin-left: auto; display: flex; gap: 12px; font-size: 12px; color: var(--muted); flex-wrap: wrap; }
.legend i { display: inline-block; width: 14px; height: 10px; border: 1px solid var(--line-strong); vertical-align: -1px; margin-right: 4px; }
.legend .y { background: var(--in-bg); border-color: var(--in-line); } .legend .g { background: var(--res-bg); border-color: var(--res-line); }
.toast { font-size: 12.5px; color: var(--ok); }

.cols { display: grid; grid-template-columns: minmax(0, 1fr) 360px; gap: 20px; align-items: start; }
.sheetwrap { background: var(--sheet); border: 1px solid var(--line); min-width: 0; overflow-x: auto; }
table.ws { width: 100%; border-collapse: collapse; font-size: 13.5px; }
table.ws th { text-align: left; font-size: 11px; text-transform: uppercase; letter-spacing: .06em; color: var(--muted); font-weight: 600; padding: 8px 10px; border-bottom: 1px solid var(--line-strong); background: var(--paper); white-space: nowrap; }
table.ws td { padding: 5px 10px; border-bottom: 1px solid var(--line); vertical-align: middle; }
tr.sec td { background: var(--ink); color: var(--sheet); font: 600 14px/1.2 var(--f-display); letter-spacing: .05em; text-transform: uppercase; padding: 7px 10px; }
td.n { width: 34px; color: var(--muted); font: 12px var(--f-mono); text-align: right; }
td.lbl { min-width: 180px; }
td.sym { font: italic 500 13px var(--f-mono); color: var(--ink-soft); white-space: nowrap; }
td.val { width: 200px; font: 500 13.5px var(--f-mono); font-variant-numeric: tabular-nums; text-align: right; white-space: nowrap; }
td.unit { width: 64px; color: var(--muted); font-size: 12.5px; white-space: nowrap; }
td.fx { width: 34px; text-align: center; }
tr.key td { background: var(--res-bg); }
tr.key td.lbl { font-weight: 600; }
tr.key td.val { font-weight: 700; }
tr.inrow td.val { background: var(--in-bg); padding: 2px 4px; }
tr.inrow td.val input, tr.inrow td.val select { width: 100%; border: 1px solid var(--in-line); background: var(--sheet); padding: 4px 8px; border-radius: 3px; font: 500 13.5px var(--f-mono); text-align: right; }
tr.inrow td.val select { text-align: left; font-family: var(--f-body); font-size: 13px; }
tr.inrow td.val input.bad { border-color: var(--bad); background: var(--bad-bg); }
tr.inrow.changed td.n { color: var(--ink); font-weight: 700; }
tr.note td { padding: 0 10px 7px; border-bottom: 1px solid var(--line); }
tr.has-note td { border-bottom: 0; }
.notes { font-size: 12.5px; color: var(--muted); }
.notes .ex { display: block; font: 11.5px/1.45 var(--f-mono); color: var(--ink-soft); margin-top: 2px; word-break: break-word; }
.fxbtn { border: 0; background: none; cursor: pointer; color: var(--muted); font: italic 600 13px var(--f-mono); padding: 2px 6px; border-radius: 3px; }
.fxbtn:hover, .fxbtn.on { background: var(--paper); color: var(--ink); }
.chip { display: inline-block; padding: 2px 9px; border-radius: 999px; font: 700 11.5px/1.5 var(--f-body); letter-spacing: .03em; white-space: nowrap; }
.chip.ok { background: var(--ok-bg); color: var(--ok); } .chip.bad { background: var(--bad-bg); color: var(--bad); } .chip.warn { background: var(--warn-bg); color: var(--warn); }
.err { color: var(--bad); cursor: help; }
table.grid { border-collapse: collapse; font: 12.5px var(--f-mono); margin: 6px 10px 12px; }
table.grid td { border: 1px solid var(--line); padding: 0; text-align: right; }
table.grid td.h { background: var(--paper); font: 600 11px var(--f-body); color: var(--muted); padding: 5px 6px; text-align: center; }
table.grid td.c { padding: 4px 6px; min-width: 64px; }
table.grid td.i { background: var(--in-bg); }
table.grid td.i input { width: 76px; border: 0; background: transparent; padding: 4px 6px; text-align: right; font: inherit; }

/* cột phải */
.aside { position: sticky; top: calc(env(safe-area-inset-top, 0px) + 12px); display: flex; flex-direction: column; gap: 14px; }
.panel { background: var(--sheet); border: 1px solid var(--line); }
.panel > h3 { margin: 0; padding: 8px 12px; font: 600 13px/1.2 var(--f-display); letter-spacing: .08em; text-transform: uppercase; color: var(--ink); border-bottom: 1px solid var(--line); display: flex; justify-content: space-between; gap: 8px; align-items: center; }
.fig { padding: 8px; background: #fff; }
.fig img { display: block; width: 100%; height: auto; cursor: zoom-in; }
.verdict { padding: 12px; display: flex; gap: 10px; align-items: center; font-weight: 600; }
.verdict.ok { background: var(--ok-bg); color: var(--ok); } .verdict.bad { background: var(--bad-bg); color: var(--bad); }
.verdict big { font: 600 28px/1 var(--f-display); }
.krs { list-style: none; margin: 0; padding: 4px 0; }
.krs li { display: grid; grid-template-columns: 1fr auto; gap: 8px; padding: 6px 12px; border-bottom: 1px dashed var(--line); font-size: 13px; }
.krs li:last-child { border-bottom: 0; }
.krs li span { color: var(--muted); min-width: 0; }
.krs li span i { font: italic 500 12px var(--f-mono); color: var(--ink-soft); }
.krs li b { font: 600 13.5px var(--f-mono); font-variant-numeric: tabular-nums; text-align: right; white-space: nowrap; }
.krs li b small { font: 400 11.5px var(--f-body); color: var(--muted); margin-left: 3px; }

.lightbox { position: fixed; inset: 0; background: rgba(10, 16, 22, .82); display: grid; place-items: center; padding: 20px; z-index: 50; cursor: zoom-out; }
.lightbox img { max-width: min(1100px, 100%); max-height: 100%; background: #fff; padding: 10px; }
.foot { margin-top: 40px; font-size: 12px; color: var(--muted); border-top: 1px solid var(--line); padding-top: 12px; max-width: 1100px; }

@media (max-width: 1180px) {
  .cols { grid-template-columns: 1fr; }
  .aside { position: static; display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); }
}
@media (max-width: 860px) {
  .app { grid-template-columns: 1fr; }
  .side { position: fixed; inset: 0 auto 0 0; width: min(320px, 88vw); z-index: 40; transform: translateX(-100%); transition: transform .2s; box-shadow: 0 0 40px rgba(0,0,0,.25); padding-top: env(safe-area-inset-top, 0px); }
  .side.open { transform: none; }
  .topbar { display: flex; gap: 10px; align-items: center; position: sticky; top: env(safe-area-inset-top, 0px); z-index: 30; background: var(--paper); padding: 10px 0; border-bottom: 1px solid var(--line); margin-bottom: 14px; }
  .topbar b { font: 600 18px var(--f-display); text-transform: uppercase; color: var(--ink); }
  .main { padding-inline: 16px; padding-block: 0 50px; }
  .tblock .code { font-size: 22px; padding: 8px 12px; }
  .tblock h1 { font-size: 22px; }
  .home h1 { font-size: 32px; }
  td.lbl { min-width: 130px; }
  td.val { width: 140px; }
  .legend { margin-left: 0; }
}
td.lbl .lsym { display: none; font: italic 500 12px var(--f-mono); color: var(--ink-soft); }
.gridwrap { overflow-x: auto; border-bottom: 1px solid var(--line); }
@media (max-width: 600px) {
  table.ws th:nth-child(1), table.ws th:nth-child(3), table.ws th:nth-child(6), td.n, td.sym, td.fx { display: none; }
  td.lbl { min-width: 0; padding-right: 4px; } td.lbl .lsym { display: inline; }
  td.val { width: 118px; } td.unit { width: auto; padding-left: 4px; }
  tr.note td.notes { padding-left: 10px; }
}
@media (prefers-reduced-motion: reduce) { .side { transition: none; } }

/* ---------- trang nhiều trang: đường dẫn, bài giải thích */
.topbar a { text-decoration: none; }
.crumbs { font-size: 12.5px; color: var(--muted); margin: 0 0 12px; display: flex; flex-wrap: wrap; gap: 6px; }
.crumbs a { color: var(--muted); text-decoration: none; } .crumbs a:hover { color: var(--ink); text-decoration: underline; }
.crumbs span:last-child { color: var(--text); }
.main > .foot { margin-top: 48px; }
.pn { display: flex; flex-wrap: wrap; gap: 8px; justify-content: space-between; margin: 28px 0 0; max-width: 1320px; }
.pn .btn { text-decoration: none; color: var(--text); }
a.btn { display: inline-block; }

.explain { max-width: 860px; margin-top: 34px; font-size: 15px; line-height: 1.65; }
.explain.knowledge { margin-top: 0; }
.explain .exh { border-top: 2px solid var(--ink); padding-top: 14px; margin-bottom: 8px; }
.explain.knowledge .exh { border-top: 0; padding-top: 0; }
.explain .kicker { font: 600 13px/1.2 var(--f-display); letter-spacing: .08em; text-transform: uppercase; color: var(--ink-soft); }
.explain h1 { font: 600 36px/1.08 var(--f-display); text-transform: uppercase; color: var(--ink); margin: 6px 0 10px; text-wrap: balance; }
.explain .ext { font: 600 26px/1.1 var(--f-display); text-transform: uppercase; color: var(--ink); margin: 0 0 10px; text-wrap: balance; }
.intoc { display: flex; flex-wrap: wrap; gap: 6px; margin: 4px 0 6px; }
.intoc a { font-size: 12.5px; padding: 3px 10px; border: 1px solid var(--line-strong); border-radius: 999px; text-decoration: none; color: var(--ink); background: var(--sheet); }
.intoc a:hover { border-color: var(--ink); }
.explain h2 { font: 600 22px/1.15 var(--f-display); text-transform: uppercase; letter-spacing: .02em; color: var(--ink); margin: 30px 0 8px; padding-bottom: 4px; border-bottom: 1px solid var(--line); scroll-margin-top: 70px; text-wrap: balance; }
.explain h3 { font-size: 15.5px; font-weight: 700; margin: 20px 0 4px; color: var(--text); }
.explain p { margin: 8px 0; max-width: 72ch; }
.explain ul, .explain ol { padding-left: 22px; max-width: 72ch; }
.explain li { margin: 4px 0; } .explain li p { margin: 0; }
.explain blockquote { margin: 10px 0; padding: 10px 16px; background: var(--sheet); border: 1px solid var(--line); border-left: 4px solid var(--ink); font: 500 15px/1.5 var(--f-mono); overflow-x: auto; }
.explain blockquote p { margin: 0; max-width: none; }
.explain .step { font-weight: 700; }
.explain a { color: var(--ink); text-underline-offset: 2px; }
.callout { margin: 14px 0; padding: 12px 16px; border-radius: 4px; background: var(--sheet); border: 1px solid var(--line); max-width: 72ch; }
.callout > b { display: block; font: 600 13px/1.2 var(--f-display); letter-spacing: .08em; text-transform: uppercase; margin-bottom: 4px; }
.callout p { margin: 4px 0; }
.callout.imagine { background: var(--in-bg); border-color: var(--in-line); } .callout.imagine > b { color: var(--warn); }
.callout.remember { border-left: 4px solid var(--ink); } .callout.remember > b { color: var(--ink); }
.callout.result { background: var(--res-bg); border-color: var(--res-line); } .callout.result > b { color: var(--ok); }
.callout.note > b { color: var(--muted); }
.tbl { overflow-x: auto; margin: 12px 0; border: 1px solid var(--line); background: var(--sheet); }
.tbl table { border-collapse: collapse; width: 100%; font-size: 13.5px; line-height: 1.45; }
.tbl th { text-align: left; background: var(--paper); font-size: 12px; color: var(--muted); padding: 7px 10px; border-bottom: 1px solid var(--line-strong); }
.tbl td { padding: 6px 10px; border-bottom: 1px solid var(--line); vertical-align: top; }
.tbl tr:last-child td { border-bottom: 0; }
.tbl td strong { font-family: var(--f-mono); font-variant-numeric: tabular-nums; }
.tbl p { margin: 0; }
figure.fig-gt { margin: 18px 0; max-width: 640px; }
figure.fig-gt img { display: block; width: 100%; height: auto; background: #fff; border: 1px solid var(--line); cursor: zoom-in; }
figure.fig-gt figcaption { font-size: 12.5px; color: var(--muted); margin-top: 6px; font-style: italic; }
.home h3.hg { margin: 18px 0 0; font-size: 14px; color: var(--ink); }
.home .hnote { margin-top: 2px; }
.srcs { max-width: 72ch; }
@media (max-width: 860px) {
  .explain { font-size: 14.5px; }
  .explain h1 { font-size: 28px; }
  .explain .ext { font-size: 21px; }
}