/* Layout: ghi chú làm việc một cột, mục lục dính bên trái ở màn rộng; bảng là nội dung chính nên được ưu tiên độ rộng. */
:root{
  --bg:#f7f8f7; --bg2:#eef1ef; --fg:#1d2522; --fg2:#55605c; --line:#d6dcd9;
  --accent:#176b5c; --accent-soft:#dcefe9; --warn:#9a5b10; --warn-soft:#f6ead6; --ok:#2d6a3e;
  --display:"Fraunces",Georgia,serif; --body:"Be Vietnam Pro",system-ui,Segoe UI,sans-serif; --mono:"JetBrains Mono",ui-monospace,Menlo,monospace;
  color-scheme:light;
}
@media (prefers-color-scheme:dark){:root:not([data-theme="light"]){
  --bg:#141917; --bg2:#1c2320; --fg:#e4e9e6; --fg2:#9aa6a1; --line:#2c3632;
  --accent:#5fc4ad; --accent-soft:#1d3a33; --warn:#e0a24a; --warn-soft:#3a2d14; --ok:#7fc58f; color-scheme:dark}}
:root[data-theme="dark"]{
  --bg:#141917; --bg2:#1c2320; --fg:#e4e9e6; --fg2:#9aa6a1; --line:#2c3632;
  --accent:#5fc4ad; --accent-soft:#1d3a33; --warn:#e0a24a; --warn-soft:#3a2d14; --ok:#7fc58f; color-scheme:dark}
*{box-sizing:border-box}
html,body{margin:0}
body{background:var(--bg);color:var(--fg);font:16px/1.65 var(--body);padding-block:0 4rem;padding-left:max(16px,env(safe-area-inset-left,0px));padding-right:max(16px,env(safe-area-inset-right,0px))}
.wrap{max-width:1180px;margin:0 auto;display:grid;grid-template-columns:240px minmax(0,1fr);gap:3rem}
@media (max-width:900px){.wrap{grid-template-columns:minmax(0,1fr)}nav.toc{position:static;max-height:none;border-right:0;border-bottom:1px solid var(--line);padding-bottom:1rem}}
nav.toc{position:sticky;top:0;align-self:start;max-height:100vh;overflow:auto;padding-top:2.5rem;font-size:.9rem;border-right:1px solid var(--line);padding-right:1rem}
nav.toc .k{font-size:.7rem;letter-spacing:.12em;text-transform:uppercase;color:var(--fg2);margin-bottom:.6rem}
nav.toc ol{list-style:none;margin:0;padding:0;display:grid;gap:.35rem}
nav.toc a{color:var(--fg2);text-decoration:none}
nav.toc a:hover,nav.toc a:focus-visible{color:var(--accent)}
main{min-width:0;padding-top:2.5rem}
header.hero{border-bottom:1px solid var(--line);padding-bottom:1.5rem;margin-bottom:2rem}
.eyebrow{font-family:var(--mono);font-size:.78rem;color:var(--accent);letter-spacing:.04em}
h1{font-family:var(--display);font-weight:600;font-size:clamp(2rem,4vw,2.9rem);line-height:1.12;margin:.4rem 0 .8rem;text-wrap:balance;font-variation-settings:"opsz" 144}
.lede{font-size:1.08rem;color:var(--fg2);max-width:62ch;margin:0}
.meta{font-family:var(--mono);font-size:.78rem;color:var(--fg2);margin-top:1rem}
section{margin-bottom:3rem}
h2{font-family:var(--display);font-weight:600;font-size:1.7rem;line-height:1.2;margin:0 0 1rem;text-wrap:balance;scroll-margin-top:1rem}
h2 .n{font-family:var(--mono);font-size:.85rem;color:var(--accent);display:block;margin-bottom:.2rem}
h3{font-size:1.05rem;font-weight:600;margin:1.6rem 0 .5rem}
p,li{max-width:70ch}
ul,ol{padding-left:1.3rem}
li{margin-bottom:.35rem}
strong{font-weight:600}
code{font-family:var(--mono);font-size:.86em;background:var(--bg2);padding:.1em .35em;border-radius:3px}
pre{font-family:var(--mono);font-size:.82rem;line-height:1.5;background:var(--bg2);border:1px solid var(--line);padding:1rem;border-radius:4px;overflow-x:auto;max-width:100%}
.tbl{overflow-x:auto;margin:1rem 0 1.4rem;border:1px solid var(--line);border-radius:4px}
table{border-collapse:collapse;width:100%;font-size:.9rem;min-width:560px}
th,td{text-align:left;vertical-align:top;padding:.55rem .7rem;border-bottom:1px solid var(--line)}
th{background:var(--bg2);font-weight:600;font-size:.8rem;letter-spacing:.03em;text-transform:uppercase;color:var(--fg2)}
tr:last-child td{border-bottom:0}
td:first-child{font-weight:600;white-space:nowrap}
.num{font-variant-numeric:tabular-nums;font-family:var(--mono);font-size:.84em}
.callout{border-left:3px solid var(--accent);background:var(--accent-soft);padding:.8rem 1rem;border-radius:0 4px 4px 0;margin:1.2rem 0;max-width:72ch}
.callout.warn{border-color:var(--warn);background:var(--warn-soft)}
.callout p{margin:.3rem 0}
.gates{display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));gap:.8rem;margin:1rem 0}
.gate{border:1px solid var(--line);border-radius:4px;padding:.8rem 1rem;background:var(--bg2)}
.gate b{display:block;font-family:var(--mono);font-size:.78rem;color:var(--accent);margin-bottom:.3rem}
.gate p{margin:0;font-size:.92rem}
.phase{display:grid;grid-template-columns:3.2rem minmax(0,1fr);gap:.8rem;padding:.9rem 0;border-top:1px solid var(--line)}
.phase:last-child{border-bottom:1px solid var(--line)}
.phase .p{font-family:var(--display);font-size:1.6rem;color:var(--accent);line-height:1}
.phase h4{margin:0 0 .3rem;font-size:1rem}
.phase p{margin:.2rem 0;font-size:.95rem}
.phase .exit{font-size:.88rem;color:var(--fg2)}
.phase .exit b{color:var(--ok)}
footer{border-top:1px solid var(--line);margin-top:3rem;padding-top:1rem;font-size:.85rem;color:var(--fg2)}
a{color:var(--accent)}
:focus-visible{outline:2px solid var(--accent);outline-offset:2px}
@media (prefers-reduced-motion:no-preference){html{scroll-behavior:smooth}}
/* bổ sung 2026-11-07 (soạn lại): ví dụ, nhãn, lưới 2 cột */
.ex{border:1px dashed var(--line);border-radius:4px;padding:.8rem 1rem;margin:1.2rem 0;max-width:72ch;background:transparent}
.ex .k{font-family:var(--mono);font-size:.72rem;letter-spacing:.1em;text-transform:uppercase;color:var(--warn);margin-bottom:.3rem}
.ex p{margin:.3rem 0}
.muted{color:var(--fg2)}
.cols{display:grid;grid-template-columns:repeat(auto-fit,minmax(260px,1fr));gap:1rem 2rem}
.one{font-family:var(--display);font-size:1.15rem;line-height:1.4;border-top:1px solid var(--line);padding-top:1rem;margin-top:1.5rem;max-width:62ch}