/* Dùng chung cho /kien-thuc/ và mọi bài viết trong /kien-thuc/<slug>/ */
:root{
  --brand:#0b4f8a; --brand-d:#083a66; --brand-l:#e8f1fa;
  --accent:#38bdf8; --accent-d:#0ea5e9;
  --ink:#0a1f33; --muted:#5b6b7c; --line:#dde6ef;
  --bg:#ffffff; --bg-soft:#f5f8fb;
  --radius:16px; --shadow:0 6px 24px rgba(10,31,51,.08);
}
*{box-sizing:border-box}
body{margin:0;font-family:"Be Vietnam Pro",system-ui,-apple-system,"Segoe UI",Roboto,sans-serif;color:var(--ink);background:var(--bg);line-height:1.7;font-size:17px}
img{max-width:100%;display:block}
a{color:var(--brand)}
.wrap{max-width:1120px;margin:0 auto;padding:0 16px}
.narrow{max-width:760px;margin:0 auto;padding:0 16px}
h1,h2,h3{line-height:1.3;margin:0 0 12px}

/* Buttons */
.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;padding:12px 20px;border-radius:999px;font-weight:700;text-decoration:none;border:0;cursor:pointer;font-size:1rem;transition:background .15s}
.btn-primary{background:var(--accent);color:var(--ink)}
.btn-primary:hover{background:var(--accent-d)}
.btn-brand{background:var(--brand);color:#fff}
.btn-brand:hover{background:var(--brand-d)}
.btn-ghost{background:transparent;color:#fff;border:2px solid rgba(255,255,255,.7)}

/* Header */
header.top{position:sticky;top:0;z-index:50;background:rgba(255,255,255,.95);backdrop-filter:blur(8px);border-bottom:1px solid var(--line)}
.nav{display:flex;align-items:center;justify-content:space-between;height:64px;gap:16px}
.logo{display:flex;align-items:center;gap:10px;text-decoration:none;color:var(--ink);white-space:nowrap}
.logo img{width:44px;height:44px;object-fit:contain}
.logo b{display:block;font-weight:900;font-size:1.15rem;line-height:1;color:var(--brand)}
.logo b span{color:var(--accent)}
.logo small{display:block;font-weight:800;font-size:.55rem;letter-spacing:.12em;margin-top:5px;color:var(--accent);text-transform:uppercase;line-height:1}
.menu{display:none;gap:22px;font-weight:600;font-size:.95rem}
.menu a{text-decoration:none;color:var(--muted)}
.menu a:hover,.menu a[aria-current]{color:var(--brand)}
.nav .btn{padding:10px 16px;font-size:.92rem;white-space:nowrap}
@media (min-width:880px){.menu{display:flex}}

/* Breadcrumb */
.crumb{font-size:.85rem;color:var(--muted);padding:18px 0 0}
.crumb ol{list-style:none;padding:0;margin:0;display:flex;flex-wrap:wrap;gap:6px}
.crumb li+li::before{content:"›";margin-right:6px}
.crumb a{color:var(--muted);text-decoration:none}
.crumb a:hover{color:var(--brand)}

/* Listing */
.blog-head{padding:28px 0 8px}
.blog-head h1{font-size:clamp(1.7rem,4.5vw,2.4rem);font-weight:800}
.blog-head p{color:var(--muted);max-width:660px;margin:0}
.filters{display:flex;flex-wrap:wrap;gap:8px;margin:24px 0 8px}
.filters button{font:inherit;font-size:.88rem;font-weight:600;padding:7px 14px;border-radius:999px;border:1.5px solid var(--line);background:#fff;color:var(--muted);cursor:pointer}
.filters button[aria-pressed="true"]{background:var(--brand);border-color:var(--brand);color:#fff}
.posts{display:grid;gap:20px;margin:20px 0 56px}
@media (min-width:700px){.posts{grid-template-columns:1fr 1fr}}
@media (min-width:1000px){.posts{grid-template-columns:repeat(3,1fr)}}
.post{display:flex;flex-direction:column;background:#fff;border:1px solid var(--line);border-radius:var(--radius);overflow:hidden;box-shadow:var(--shadow);text-decoration:none;color:inherit;transition:transform .15s}
.post:hover{transform:translateY(-3px)}
.post-cover{aspect-ratio:16/9;display:grid;place-items:center;font-size:2.6rem;background:linear-gradient(135deg,var(--brand-d),var(--brand) 60%,#1673c4);color:#fff}
.post-body{padding:18px 20px 22px;display:flex;flex-direction:column;gap:8px;flex:1}
.post h2{font-size:1.12rem;margin:0}
.post p{margin:0;color:var(--muted);font-size:.93rem;line-height:1.6;flex:1}
.meta{display:flex;flex-wrap:wrap;gap:6px 12px;align-items:center;font-size:.8rem;color:var(--muted)}
.cat{display:inline-block;background:var(--brand-l);color:var(--brand);font-weight:700;font-size:.75rem;padding:3px 10px;border-radius:999px}

/* Article */
.art-head{padding:20px 0 8px}
.art-head h1{font-size:clamp(1.65rem,4.6vw,2.35rem);font-weight:800;margin:10px 0 14px}
.art-head .sapo{font-size:1.1rem;color:var(--muted);margin:0 0 14px}
.toc{background:var(--bg-soft);border:1px solid var(--line);border-radius:14px;padding:16px 20px;margin:24px 0}
.toc b{display:block;margin-bottom:6px}
.toc ol{margin:0;padding-left:20px}
.toc a{text-decoration:none}
.toc a:hover{text-decoration:underline}
article.content{padding-bottom:16px}
.content h2{font-size:1.45rem;font-weight:800;margin:36px 0 12px;scroll-margin-top:80px}
.content h3{font-size:1.15rem;margin:24px 0 8px}
.content p,.content li{color:#1e3347}
.content ul,.content ol{padding-left:22px}
.content li{margin-bottom:6px}
.tbl{overflow-x:auto;margin:16px 0;border:1px solid var(--line);border-radius:12px}
.tbl table{border-collapse:collapse;width:100%;font-size:.93rem;min-width:520px}
.tbl th,.tbl td{padding:10px 12px;text-align:left;border-bottom:1px solid var(--line);vertical-align:top}
.tbl th{background:var(--brand-l);color:var(--brand-d);font-weight:700}
.tbl tr:last-child td{border-bottom:0}
.callout{border-left:4px solid var(--accent);background:var(--brand-l);padding:14px 18px;border-radius:0 12px 12px 0;margin:20px 0}
.callout p{margin:0}
.warn{border-left-color:#e5383b;background:#fdecec}

/* FAQ trong bài */
.faq details{border:1px solid var(--line);border-radius:12px;padding:2px 18px;margin-bottom:10px}
.faq summary{cursor:pointer;font-weight:700;padding:12px 0}
.faq details p{margin:0 0 14px;color:var(--muted)}

/* CTA cuối bài */
.cta{background:linear-gradient(135deg,var(--brand-d),var(--brand));color:#fff;border-radius:20px;padding:26px;margin:36px 0}
.cta h2{color:#fff;font-size:1.35rem;margin:0 0 8px}
.cta p{color:rgba(255,255,255,.88);margin:0 0 18px}
.cta-btns{display:flex;flex-wrap:wrap;gap:10px}

.related{border-top:1px solid var(--line);padding:28px 0 56px}
.related h2{font-size:1.2rem}
.related ul{list-style:none;padding:0;margin:0;display:grid;gap:10px}
.related a{display:block;padding:14px 16px;border:1px solid var(--line);border-radius:12px;text-decoration:none;font-weight:600}
.related a:hover{border-color:var(--brand)}
.disclaimer{font-size:.82rem;color:var(--muted)}

/* Footer */
footer{background:#06111d;color:rgba(255,255,255,.7);padding:36px 0 100px;font-size:.9rem}
@media (min-width:880px){footer{padding-bottom:36px}}
footer a{color:inherit;text-decoration:none}
footer a:hover{color:#fff}
.foot-links{display:flex;flex-wrap:wrap;gap:8px 20px;margin:10px 0 0;padding:0;list-style:none}

/* Thanh liên hệ dưới đáy (mobile) */
.bar{position:fixed;left:0;right:0;bottom:0;z-index:60;display:flex;background:#fff;border-top:1px solid var(--line);box-shadow:0 -6px 20px rgba(0,0,0,.08)}
.bar a{flex:1;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:2px;padding:8px 4px;font-size:.75rem;font-weight:700;text-decoration:none}
.bar a[hidden]{display:none}
.bar svg{width:22px;height:22px}
.bar .b-call{color:#e5383b}
.bar .b-zalo{color:#0068ff}
.bar .b-msg{color:#a334fa}
.bar .b-reg{flex:1.3;background:var(--accent);color:var(--ink);font-size:.88rem}
@media (min-width:880px){.bar{display:none}}

@media (prefers-reduced-motion:reduce){*{transition:none!important}}
@media (max-width:479px){.nav .btn .num{display:none}.nav .btn::after{content:"Gọi"}}
@media (max-width:699px){.post-cover{aspect-ratio:3/1}}