:root{--bg:#fbfaf9;--surface:#fff;--ink:#1c1817;--muted:#6b605c;--line:#e8e1dd;--steel:#8e2f1d;--rust:#b0402a;--zalo:#0b68d8;--tint:#fbf1ee;color-scheme:light;
--f-display:"Barlow Condensed","Arial Narrow",Arial,sans-serif;--f-body:"Be Vietnam Pro",system-ui,-apple-system,"Segoe UI",Roboto,sans-serif}
*{box-sizing:border-box}html{-webkit-text-size-adjust:100%}
body{margin:0;background:var(--bg);color:var(--ink);font-family:var(--f-body);font-size:17px;line-height:1.75}
img{max-width:100%;height:auto;display:block}a{color:var(--rust)}
:focus-visible{outline:3px solid var(--rust);outline-offset:3px}
.wrap{max-width:1160px;margin:0 auto;padding-inline:20px}
h1,h2,h3{font-family:var(--f-display);font-weight:700;line-height:1.1;text-wrap:balance;letter-spacing:.005em}
.topbar{background:var(--steel);color:#fff;font-size:.85rem}.topbar .wrap{display:flex;flex-wrap:wrap;justify-content:space-between;gap:4px 18px;padding-block:7px}.topbar a{color:#fff;text-decoration:none}
header.top{position:sticky;top:0;z-index:20;background:var(--surface);border-bottom:1px solid var(--line)}
.nav{display:flex;align-items:center;justify-content:space-between;gap:16px;min-height:64px}
.nav .logo img{height:40px;width:auto;max-width:calc(100vw - 150px)}
.nav ul{display:flex;gap:22px;list-style:none;margin:0;padding:0}.nav ul a{color:var(--ink);text-decoration:none;font-weight:500;font-size:.93rem}.nav ul a:hover,.nav ul a[aria-current]{color:var(--rust)}
.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;background:var(--rust);color:#fff;font-weight:600;text-decoration:none;padding:12px 22px;border-radius:2px;font-size:.95rem}
.btn:hover{filter:brightness(1.08)}.btn.zalo{background:var(--zalo)}.btn.ghost{background:transparent;color:var(--ink);border:1.5px solid var(--ink)}
@media (max-width:900px){.nav ul{display:none}}
@media (max-width:520px){.nav>.btn{padding:9px 12px;font-size:.85rem}}
.crumbs{font-size:.85rem;color:var(--muted);padding-top:22px}.crumbs a{color:var(--muted)}.crumbs span{margin-inline:6px}
article.post{max-width:760px;margin:0 auto;padding:10px 0 40px}
.post .cat{font-family:var(--f-display);text-transform:uppercase;letter-spacing:.14em;font-size:.95rem;font-weight:600;color:var(--rust)}
.post h1{font-size:clamp(2.1rem,5vw,3.1rem);margin:.25em 0 .35em}
.meta{color:var(--muted);font-size:.9rem;display:flex;flex-wrap:wrap;gap:4px 14px}
.post .hero{margin:24px 0 8px;aspect-ratio:16/9;overflow:hidden;border-radius:2px;background:var(--line)}.post .hero img{width:100%;height:100%;object-fit:cover}
.tldr{background:var(--tint);border-left:4px solid var(--rust);padding:16px 20px;margin:26px 0}
.tldr p{margin:0 0 6px;font-family:var(--f-display);font-weight:700;font-size:1.15rem;text-transform:uppercase;letter-spacing:.06em;color:var(--steel)}
.tldr ul{margin:0;padding-left:1.2em}.tldr li{margin:4px 0}
.post h2{font-size:clamp(1.6rem,3.6vw,2.1rem);margin:1.6em 0 .4em}.post h3{font-size:1.35rem;font-weight:600;margin:1.3em 0 .3em}
.post p{margin:0 0 1em}.post ul,.post ol{padding-left:1.3em;margin:0 0 1em}.post li{margin:.3em 0}
.post figure{margin:22px 0}.post figure img{width:100%;max-height:520px;object-fit:cover;border-radius:2px;background:var(--line)}
.post figcaption{font-size:.85rem;color:var(--muted);margin-top:6px}
.table-wrap{overflow-x:auto;margin:18px 0 22px;border:1px solid var(--line);background:var(--surface)}
table{border-collapse:collapse;width:100%;min-width:520px;font-size:.93rem;line-height:1.5}
th,td{text-align:left;padding:10px 12px;border-bottom:1px solid var(--line);vertical-align:top}th{background:var(--tint);font-weight:600}tr:last-child td{border-bottom:0}
.formula{font-family:var(--f-display);font-size:1.45rem;font-weight:600;background:var(--surface);border:1px dashed var(--rust);padding:12px 16px;text-align:center;color:var(--steel)}
.note{font-size:.92rem;color:var(--muted)}
.callout{background:var(--surface);border:1px solid var(--line);border-left:4px solid var(--rust);padding:16px 20px;margin:22px 0}
.yt{position:relative;aspect-ratio:16/9;background:#000;margin:18px 0 12px}.yt button{all:unset;cursor:pointer;position:absolute;inset:0;display:block}
.yt img{width:100%;height:100%;object-fit:cover;opacity:.85}.yt iframe{position:absolute;inset:0;width:100%;height:100%;border:0}
.play{position:absolute;left:50%;top:50%;width:72px;height:50px;margin:-25px 0 0 -36px;background:var(--rust);border-radius:12px}
.play::after{content:"";position:absolute;left:29px;top:15px;border-style:solid;border-width:10px 0 10px 17px;border-color:transparent transparent transparent #fff}
.faq{margin-top:2.2em}.faq details{border-top:1px solid var(--line);padding:12px 0}.faq details:last-child{border-bottom:1px solid var(--line)}
.faq summary{cursor:pointer;font-weight:600;list-style-position:outside}.faq details p{margin:.6em 0 0}
.cta{background:var(--steel);color:#fff;padding:26px 24px;margin:36px 0 10px;border-radius:2px}
.cta h2{margin:0 0 .3em;color:#fff;font-size:1.9rem}.cta p{margin:0 0 16px;opacity:.92}.cta .row{display:flex;flex-wrap:wrap;gap:10px}
.cta .btn{background:#fff;color:var(--steel)}.cta .btn.zalo{background:var(--zalo);color:#fff}.cta .btn.ghost{background:transparent;color:#fff;border-color:#fff}
.share{display:flex;flex-wrap:wrap;align-items:center;gap:8px;margin:24px 0 0;font-size:.9rem;color:var(--muted)}
.share a,.share button{font:inherit;font-size:.88rem;color:var(--ink);background:var(--surface);border:1px solid var(--line);padding:6px 12px;border-radius:2px;cursor:pointer;text-decoration:none}
.related{border-top:1px solid var(--line);padding:40px 0 60px}
.related h2{font-size:2rem;margin:0 0 20px}
.kt-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:20px}
@media (max-width:900px){.kt-grid{grid-template-columns:1fr 1fr}}@media (max-width:560px){.kt-grid{grid-template-columns:1fr}}
.kt{display:flex;flex-direction:column;background:var(--surface);border:1px solid var(--line);text-decoration:none;color:var(--ink);transition:border-color .15s}
.kt:hover{border-color:var(--rust)}.kt .im{aspect-ratio:16/10;overflow:hidden;background:var(--line)}.kt .im img{width:100%;height:100%;object-fit:cover}
.kt .tx{padding:16px 18px 18px;display:flex;flex-direction:column;gap:8px;flex:1}
.kt .c{font-family:var(--f-display);text-transform:uppercase;letter-spacing:.12em;font-size:.82rem;font-weight:600;color:var(--rust)}
.kt h3{font-size:1.35rem;font-weight:600;margin:0;line-height:1.15}.kt p{margin:0;color:var(--muted);font-size:.93rem;line-height:1.6}
.kt .more{margin-top:auto;padding-top:6px;font-weight:600;font-size:.9rem;color:var(--rust)}
.list-head{padding:28px 0 26px}.list-head h1{font-size:clamp(2.3rem,5vw,3.3rem);margin:.15em 0 .3em}.list-head p{color:var(--muted);max-width:62ch;margin:0}
footer{background:var(--ink);color:var(--bg);padding-block:40px 96px;font-size:.88rem;line-height:1.7}
footer a{color:var(--bg)}footer .cols{display:grid;grid-template-columns:2fr 1fr 1fr;gap:28px}footer h3{font-size:1.1rem;letter-spacing:.06em;text-transform:uppercase;margin:0 0 8px}
footer ul{list-style:none;margin:0;padding:0}footer p{margin:0}footer .copy{margin-top:28px;padding-top:14px;border-top:1px solid rgba(127,127,127,.35);opacity:.75}
@media (max-width:760px){footer .cols{grid-template-columns:1fr}}
.float{position:fixed;right:16px;bottom:16px;z-index:30;display:flex;flex-direction:column;gap:10px}
.float a{display:flex;align-items:center;padding:11px 16px;border-radius:999px;color:#fff;text-decoration:none;font-weight:600;font-size:.9rem;box-shadow:0 4px 14px rgba(0,0,0,.18)}
.float .zl{background:var(--zalo)}.float .cl{background:var(--rust)}
@media (max-width:700px){.float{left:0;right:0;bottom:0;flex-direction:row;gap:0;padding-bottom:env(safe-area-inset-bottom,0px);background:var(--surface)}.float a{flex:1;justify-content:center;border-radius:0;box-shadow:none}}