:root{
  --c:#4f46e5;--c2:#7c3aed;--ink:#0f172a;--muted:#64748b;--line:#e2e8f0;--bg:#f8fafc;--card:#fff;
  --ok:#16a34a;--warn:#d97706;--bad:#dc2626;--r:14px;--sh:0 1px 2px rgba(15,23,42,.04),0 4px 16px rgba(15,23,42,.06);
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;font:16px/1.6 system-ui,-apple-system,"Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif;color:var(--ink);background:var(--bg)}
a{color:var(--c);text-decoration:none}
a:hover{text-decoration:underline}
img{max-width:100%;height:auto}
h1,h2,h3{line-height:1.25;margin:0 0 .5em}
h1{font-size:clamp(1.7rem,3.5vw,2.6rem)}
h2{font-size:1.5rem}
h3{font-size:1.1rem}
code{background:#f1f5f9;padding:2px 6px;border-radius:6px;font-size:.9em}
.container{max-width:1160px;margin:0 auto;padding:0 20px}
.narrow{max-width:760px}
.center{text-align:center}
.muted{color:var(--muted)}
.small{font-size:.85rem}
.hl{color:var(--c)}
.hp{position:absolute;left:-9999px;width:1px;height:1px;opacity:0}

/* Header */
.site-header{background:#fff;border-bottom:1px solid var(--line);position:sticky;top:0;z-index:20}
.nav-wrap{display:flex;align-items:center;justify-content:space-between;height:64px}
.logo{display:flex;align-items:center;gap:10px;font-weight:800;font-size:1.15rem;color:var(--ink)}
.logo:hover{text-decoration:none}
.logo-mark{display:inline-grid;place-items:center;width:34px;height:34px;border-radius:10px;background:linear-gradient(135deg,var(--c),var(--c2));color:#fff;font-size:.85rem}
.main-nav{display:flex;gap:4px}
.main-nav a{padding:8px 12px;border-radius:8px;color:var(--ink);font-weight:500}
.main-nav a:hover,.main-nav a.active{background:#eef2ff;color:var(--c);text-decoration:none}
.nav-toggle{display:none;background:none;border:0;font-size:1.6rem;cursor:pointer}
.lang-switch{display:inline-grid;place-items:center;padding:6px 12px;border:1px solid #c7d2fe;border-radius:8px;font-weight:700;font-size:.85rem;color:var(--c)}
.lang-switch:hover{background:#eef2ff;text-decoration:none}
.nav-search{max-width:1160px;margin:0 auto;padding:0 20px 12px}
.nav-search input{max-width:420px;padding:8px 14px;border-radius:99px;border:1px solid var(--line);background:var(--bg);font-size:.92rem}
textarea.out{font-family:ui-monospace,Consolas,monospace;font-size:.9rem;background:var(--bg)}
@media(max-width:860px){
  .nav-toggle{display:block}
  .main-nav{display:none;position:absolute;top:64px;left:0;right:0;background:#fff;flex-direction:column;padding:10px 20px;border-bottom:1px solid var(--line)}
  .nav-open .main-nav{display:flex}
}

/* Buttons */
.btn{display:inline-block;background:var(--c);color:#fff;border:0;border-radius:10px;padding:12px 20px;font-weight:600;font-size:1rem;cursor:pointer;transition:.15s;font-family:inherit}
.btn:hover{background:#4338ca;text-decoration:none}
.btn-ghost{background:#fff;color:var(--c);border:1px solid #c7d2fe}
.btn-ghost:hover{background:#eef2ff}
.btn-light{background:#fff;color:var(--c)}
.btn-light:hover{background:#eef2ff}
.btn-sm{padding:6px 12px;font-size:.85rem;border-radius:8px}
.btn-block{display:block;width:100%;text-align:center}
.btn-row{display:flex;gap:12px;flex-wrap:wrap;margin-top:20px}

/* Hero & sections */
.hero{background:linear-gradient(180deg,#eef2ff,#f8fafc);padding:64px 0}
.hero-grid{display:grid;grid-template-columns:1.3fr 1fr;gap:40px;align-items:center}
.hero-card{background:#fff;border-radius:20px;box-shadow:var(--sh);padding:16px;display:grid;gap:10px}
.mini-tool{display:flex;gap:12px;align-items:center;padding:14px;border-radius:12px;background:var(--bg);color:var(--ink);font-weight:600}
.mini-tool:hover{background:#eef2ff;text-decoration:none}
.mini-tool span{font-size:1.4rem}
.badge{display:inline-block;background:#fff;border:1px solid #c7d2fe;color:var(--c);padding:4px 12px;border-radius:99px;font-size:.85rem;font-weight:600;margin-bottom:14px}
.lead{font-size:1.1rem;color:#334155}
.section{padding:48px 0}
.section-alt{background:#fff;border-top:1px solid var(--line);border-bottom:1px solid var(--line)}
.section-head{display:flex;justify-content:space-between;align-items:baseline;gap:16px;margin-bottom:20px}
.page-head{background:linear-gradient(180deg,#eef2ff,#f8fafc);padding:40px 0 24px}
.crumbs{font-size:.9rem;color:var(--muted);margin-bottom:10px}
.cat-title{margin:32px 0 16px}
.cta-band{background:linear-gradient(135deg,var(--c),var(--c2));color:#fff;border-radius:20px;padding:36px;display:flex;justify-content:space-between;align-items:center;gap:24px;flex-wrap:wrap}
.cta-band p{opacity:.9;margin:0}
@media(max-width:860px){.hero-grid{grid-template-columns:1fr}.hero{padding:40px 0}}

/* Grid & cards */
.grid{display:grid;gap:20px}
.grid-3{grid-template-columns:repeat(auto-fill,minmax(280px,1fr))}
.grid-4{grid-template-columns:repeat(auto-fill,minmax(230px,1fr))}
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--r);padding:22px;box-shadow:var(--sh);color:var(--ink);display:block}
a.card:hover{border-color:#a5b4fc;transform:translateY(-2px);text-decoration:none;transition:.15s}
.card p{color:#475569;margin:.3em 0}
.tool-icon{font-size:2rem;margin-bottom:8px}
.post-card,.product-card{padding:0;overflow:hidden}
.post-card img{aspect-ratio:16/9;object-fit:cover;width:100%}
.card-body{padding:18px 20px}
.tag{display:inline-block;background:#eef2ff;color:var(--c);font-size:.75rem;font-weight:700;padding:2px 10px;border-radius:99px;margin-bottom:8px;text-transform:uppercase;letter-spacing:.03em}
.product-thumb,.product-hero{display:grid;place-items:center;aspect-ratio:16/9;font-size:4rem}
.product-hero{border-radius:var(--r);margin:10px 0 20px;font-size:6rem}
.price-row{display:flex;gap:10px;align-items:baseline;margin-top:8px}
.price{color:var(--c);font-size:1.2rem}
.big .price,.price.big{font-size:1.8rem;font-weight:800;color:var(--c);margin:10px 0}
.chips{display:flex;flex-wrap:wrap;gap:8px;margin-top:14px}
.chip{padding:6px 14px;border-radius:99px;background:#fff;border:1px solid var(--line);color:var(--ink);font-size:.9rem}
.chip.active,.chip:hover{border-color:var(--c);color:var(--c);text-decoration:none}
.check-list{list-style:none;padding:0;margin:14px 0}
.check-list li{padding:5px 0 5px 26px;position:relative}
.check-list li:before{content:"✓";position:absolute;left:0;color:var(--ok);font-weight:800}
.price-card{position:relative;display:flex;flex-direction:column}
.price-card .btn{margin-top:auto}
.price-card.featured{border:2px solid var(--c)}
.ribbon{position:absolute;top:-12px;right:16px;background:var(--c);color:#fff;padding:3px 12px;border-radius:99px;font-size:.8rem;font-weight:700}
.steps b{display:inline-grid;place-items:center;width:36px;height:36px;border-radius:50%;background:#eef2ff;color:var(--c);margin-bottom:8px}
.deal-top{display:flex;justify-content:space-between;align-items:center}
.coupon{cursor:pointer;border:1px dashed var(--c);color:var(--c);font-weight:700}

/* Layout có sidebar */
.layout-side{display:grid;grid-template-columns:minmax(0,1fr) 320px;gap:28px;align-items:start}
.layout-side aside{display:grid;gap:20px;position:sticky;top:84px}
@media(max-width:960px){.layout-side{grid-template-columns:1fr}.layout-side aside{position:static}}
.side-cta{background:linear-gradient(135deg,#eef2ff,#f5f3ff)}
.link-list{list-style:none;padding:0;margin:0}
.link-list li{padding:7px 0;border-bottom:1px solid var(--line)}
.link-list li:last-child{border:0}

/* Bài viết */
.post-title{margin-top:8px}
.post-cover{border-radius:var(--r);margin:16px 0;width:100%}
.prose{font-size:1.05rem}
.prose h2{margin-top:1.6em}
.prose h3{margin-top:1.3em}
.prose table{width:100%}
.prose.card{margin-top:24px}
.disclosure{background:#fffbeb;border:1px solid #fde68a;padding:10px 14px;border-radius:10px;font-size:.9rem}

/* Form */
.form{display:grid;gap:14px}
.form label{display:grid;gap:6px;font-weight:600;font-size:.92rem}
.form-2{display:grid;grid-template-columns:1fr 1fr;gap:14px}
@media(max-width:600px){.form-2{grid-template-columns:1fr}}
input,select,textarea{font:inherit;padding:11px 13px;border:1px solid #cbd5e1;border-radius:10px;background:#fff;width:100%;font-weight:400;color:var(--ink)}
input:focus,select:focus,textarea:focus{outline:2px solid #a5b4fc;border-color:var(--c)}
textarea.code{font-family:ui-monospace,Consolas,monospace;font-size:.9rem}
label.check{display:flex !important;align-items:center;gap:8px;font-weight:500}
label.check input{width:auto}
.alert{background:#ecfdf5;border:1px solid #a7f3d0;color:#065f46;padding:12px 16px;border-radius:10px;margin:16px 0}
.alert-error{background:#fef2f2;border-color:#fecaca;color:#991b1b}
.copy-input{font-size:.85rem;background:var(--bg)}

/* Công cụ */
.tool-box .calc{display:grid;gap:14px}
.tool-box .calc label{display:grid;gap:6px;font-weight:600;font-size:.92rem}
.tool-box h3{margin:10px 0 0}
.result{margin-top:8px}
.big-result{background:linear-gradient(135deg,#eef2ff,#f5f3ff);border-radius:12px;padding:18px;font-size:1.15rem;margin-bottom:14px}
.big-result b{color:var(--c);font-size:1.5rem}
.kv{width:100%;border-collapse:collapse}
.kv td{padding:9px 4px;border-bottom:1px solid var(--line)}
.kv td:last-child{text-align:right}
.qr{border-radius:12px;border:1px solid var(--line);background:#fff}
.pw-list{list-style:none;padding:0}
.pw-list li{display:flex;justify-content:space-between;align-items:center;gap:10px;padding:8px 0;border-bottom:1px solid var(--line)}
.pw-list code{word-break:break-all;font-size:1rem}
.pay-grid{display:grid;grid-template-columns:260px 1fr;gap:24px;align-items:start;margin-top:16px}
@media(max-width:700px){.pay-grid{grid-template-columns:1fr}}

/* Bảng */
.table-wrap{overflow-x:auto;padding:0}
.table{width:100%;border-collapse:collapse;font-size:.92rem}
.table th,.table td{padding:10px 12px;border-bottom:1px solid var(--line);text-align:left;vertical-align:top}
.table th{background:var(--bg);font-weight:700}

/* Quảng cáo */
.ad-slot{max-width:1160px;margin:24px auto;padding:0 20px;min-height:90px}
.sponsor{display:block;margin:20px 0;text-align:center}
.sponsor small{display:block;font-size:.7rem;color:var(--muted);text-transform:uppercase;letter-spacing:.05em;margin-bottom:4px}
.sponsor img{border-radius:10px;border:1px solid var(--line);max-width:100%}
.sponsor-sidebar img{width:300px}
.sponsor-house{border:2px dashed #c7d2fe;border-radius:var(--r);padding:18px;background:#fafaff;color:var(--ink);display:grid;gap:4px}
.sponsor-house:hover{border-color:var(--c);text-decoration:none}
.sponsor-house strong{color:var(--c)}
.sponsor-house span{font-size:.88rem;color:var(--muted)}
.deal-row{margin:20px 0}
.deal-mini{display:grid !important;gap:4px;padding:16px}
.deal-mini span{font-size:.88rem;color:#475569}
.donate{display:flex;gap:18px;align-items:center;margin:20px 0;background:linear-gradient(135deg,#fffbeb,#fff7ed);border-color:#fde68a}
.donate img{border-radius:10px;background:#fff;flex:none}
.donate h3{margin:0 0 4px}
@media(max-width:600px){.donate{flex-direction:column;text-align:center}}

/* Footer */
.site-footer{background:#0f172a;color:#cbd5e1;padding:48px 0 20px;margin-top:40px}
.site-footer .logo{color:#fff}
.site-footer h4{color:#fff;margin:0 0 12px}
.site-footer a{color:#cbd5e1;display:block;padding:3px 0}
.site-footer .muted{color:#94a3b8}
.footer-grid{display:grid;grid-template-columns:2fr 1fr 1fr;gap:32px}
@media(max-width:700px){.footer-grid{grid-template-columns:1fr}}
.copyright{border-top:1px solid #1e293b;margin-top:32px;padding-top:16px;font-size:.85rem;color:#94a3b8}
.zalo-float{position:fixed;right:18px;bottom:18px;background:#0068ff;color:#fff;font-weight:700;width:58px;height:58px;border-radius:50%;display:grid;place-items:center;box-shadow:0 6px 20px rgba(0,104,255,.4);z-index:30;font-size:.9rem}
.zalo-float:hover{text-decoration:none;transform:scale(1.06)}

/* Admin */
.admin-wrap{display:grid;grid-template-columns:230px 1fr;min-height:100vh}
.admin-nav{background:#0f172a;padding:20px;display:flex;flex-direction:column;gap:2px}
.admin-nav .logo{color:#fff;margin-bottom:18px}
.admin-nav a{color:#cbd5e1;padding:8px 10px;border-radius:8px}
.admin-nav a:hover{background:#1e293b;text-decoration:none}
.admin-nav hr{border:0;border-top:1px solid #1e293b;width:100%}
.admin-main{padding:28px;min-width:0}
.stat strong{display:block;font-size:1.6rem;color:var(--c)}
.todo li{margin:8px 0}
.status{padding:2px 10px;border-radius:99px;font-size:.8rem;font-weight:700}
.s-pending{background:#fef3c7;color:#92400e}
.s-paid{background:#dcfce7;color:#166534}
.s-cancelled{background:#f1f5f9;color:#64748b}
form.inline{display:inline-flex;gap:6px;margin-bottom:6px}
form.inline select{width:auto;padding:6px 10px}
@media(max-width:800px){.admin-wrap{grid-template-columns:1fr}}