/* =========================================================
   VIET BAO UI SYSTEM 2026
   Modern / Responsive / Dark mode / Admin ready
========================================================= */
:root{
 --bg:#f5f7fb;--surface:#fff;--surface-2:#f8fafc;--text:#172033;--muted:#667085;
 --border:#e7eaf0;--primary:#635bff;--primary-2:#7c3aed;--success:#16a34a;
 --danger:#ef4444;--warning:#f59e0b;--shadow:0 18px 55px rgba(15,23,42,.08);
 --radius:18px;--header:76px;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;background:var(--bg);color:var(--text);font:15px/1.7 Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",Arial,sans-serif;transition:background .2s,color .2s}
body:before{content:"";position:fixed;inset:0;pointer-events:none;background:radial-gradient(circle at 10% 0%,rgba(99,91,255,.08),transparent 28%),radial-gradient(circle at 100% 15%,rgba(124,58,237,.06),transparent 24%);z-index:-1}
a{color:inherit;text-decoration:none}
img{max-width:100%}
button,input,select,textarea{font:inherit}
.container{width:min(1180px,calc(100% - 32px));margin:auto}
.site-header{position:sticky;top:0;z-index:1000;background:rgba(255,255,255,.86);backdrop-filter:blur(18px);border-bottom:1px solid var(--border)}
.nav{min-height:var(--header);display:flex;align-items:center;justify-content:space-between;gap:20px}
.brand{display:flex;align-items:center;gap:10px;font-weight:900;font-size:20px;letter-spacing:-.3px;white-space:nowrap}
.brand b,.brand img{width:42px;height:42px;border-radius:13px;display:grid;place-items:center;object-fit:cover}
.brand b{color:#fff;background:linear-gradient(135deg,var(--primary),var(--primary-2));box-shadow:0 8px 24px rgba(99,91,255,.25)}
.main-nav{display:flex;align-items:center;gap:5px}
.main-nav>a{padding:10px 12px;border-radius:11px;color:var(--muted);font-weight:700}
.main-nav>a:hover,.main-nav>a.active{background:var(--surface-2);color:var(--text)}
.btn{display:inline-flex;align-items:center;justify-content:center;gap:7px;padding:10px 15px;border:1px solid transparent;border-radius:12px;background:linear-gradient(135deg,var(--primary),var(--primary-2));color:#fff!important;font-weight:800;box-shadow:0 8px 20px rgba(99,91,255,.2);cursor:pointer;transition:.2s}
.btn:hover{transform:translateY(-1px);filter:brightness(1.03)}
.btn-light{background:var(--surface);color:var(--text)!important;border-color:var(--border);box-shadow:none}
.theme-btn,.menu-btn{width:42px;height:42px;border:1px solid var(--border);background:var(--surface);border-radius:12px;cursor:pointer;color:var(--text)}
.menu-btn{display:none}
main{min-height:60vh}
.hero{padding:88px 0 78px;background:linear-gradient(135deg,rgba(255,255,255,.9),rgba(244,240,255,.9));border-bottom:1px solid var(--border)}
.hero h1{font-size:clamp(36px,6vw,62px);line-height:1.02;letter-spacing:-2px;max-width:820px;margin:10px 0 18px}
.hero p{max-width:720px;color:var(--muted);font-size:18px}
.eyebrow,.tag{color:var(--primary);font-weight:900;font-size:12px;text-transform:uppercase;letter-spacing:.09em}
.page{padding:42px 0 80px}
.section{display:flex;justify-content:space-between;align-items:center;gap:16px;margin:24px 0 18px}
.section h2,.section h1{margin:0;letter-spacing:-.8px}
.grid,.cards{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:20px}
.card,.featured,.panel,.form-card,.table-wrap,.stat-card{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);box-shadow:var(--shadow)}
.card{overflow:hidden;transition:.2s}
.card:hover{transform:translateY(-4px);box-shadow:0 24px 65px rgba(15,23,42,.12)}
.card img{width:100%;height:210px;object-fit:cover;background:var(--surface-2)}
.card-body{padding:20px}
.card h3{margin:7px 0 8px;line-height:1.3}
.muted{color:var(--muted)}
.featured{display:grid;grid-template-columns:1.08fr 1fr;overflow:hidden}
.featured img{width:100%;height:100%;min-height:360px;object-fit:cover}
.featured-body{padding:34px}
.search{display:flex;gap:8px;flex-wrap:wrap}
input,select,textarea{width:100%;border:1px solid var(--border);border-radius:12px;padding:12px 14px;background:var(--surface);color:var(--text);outline:none;transition:.2s}
input:focus,select:focus,textarea:focus{border-color:var(--primary);box-shadow:0 0 0 4px rgba(99,91,255,.11)}
textarea{min-height:160px;resize:vertical}
label{display:block;font-weight:800;margin:0 0 7px}
.form-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:18px}
.form-card,.panel{padding:24px}
.alert{padding:13px 15px;border-radius:13px;margin:15px 0;border:1px solid transparent}
.alert-success{background:#ecfdf3;color:#166534;border-color:#bbf7d0}.alert-error{background:#fef2f2;color:#991b1b;border-color:#fecaca}
.meta{display:flex;align-items:center;gap:10px;flex-wrap:wrap;color:var(--muted);font-size:13px}
.badge{display:inline-flex;padding:5px 9px;border-radius:999px;background:rgba(99,91,255,.1);color:var(--primary);font-size:12px;font-weight:800}
.article{max-width:860px;margin:auto}.article h1{font-size:clamp(34px,5vw,56px);line-height:1.08;letter-spacing:-1.5px}.article-content{font-size:17px}.article-content img{border-radius:16px}
.site-footer{margin-top:70px;padding:55px 0 25px;color:#cbd5e1;background:#0b1020;position:relative;overflow:hidden}
.footer-grid{display:grid;grid-template-columns:1.4fr 1fr 1fr;gap:35px}.site-footer h3{color:#fff}.site-footer a{color:#cbd5e1}.site-footer a:hover{color:#fff}
.footer-bottom{margin-top:35px;padding-top:20px;border-top:1px solid rgba(255,255,255,.1);display:flex;justify-content:space-between;gap:15px;flex-wrap:wrap}
.back-top{position:fixed;right:22px;bottom:22px;width:44px;height:44px;border:0;border-radius:50%;background:var(--primary);color:#fff;cursor:pointer;box-shadow:0 12px 30px rgba(99,91,255,.3);display:none;z-index:900}
.back-top.show{display:block}
/* admin */
.admin-shell{display:grid;grid-template-columns:245px 1fr;gap:22px;align-items:start}
.admin-sidebar{position:sticky;top:95px;background:var(--surface);border:1px solid var(--border);border-radius:20px;padding:14px;box-shadow:var(--shadow)}
.admin-sidebar .side-title{font-size:11px;text-transform:uppercase;letter-spacing:.1em;color:var(--muted);font-weight:900;padding:10px}
.admin-sidebar a{display:flex;gap:10px;align-items:center;padding:11px 12px;border-radius:12px;color:var(--muted);font-weight:750;margin:2px 0}
.admin-sidebar a:hover,.admin-sidebar a.active{background:rgba(99,91,255,.1);color:var(--primary)}
.admin-main{min-width:0}
.admin-title{display:flex;justify-content:space-between;align-items:flex-end;gap:20px;margin-bottom:20px}
.admin-title h1{margin:0;font-size:30px;letter-spacing:-1px}
.stats-grid{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:16px}
.stat-card{padding:20px}.stat-card .icon{font-size:24px}.stat-card .num{font-size:30px;font-weight:900;line-height:1.2}.stat-card .label{color:var(--muted);font-weight:700}
.table-wrap{overflow:auto}.table-wrap table{width:100%;border-collapse:collapse;min-width:720px}.table-wrap th,.table-wrap td{padding:14px 16px;border-bottom:1px solid var(--border);text-align:left}.table-wrap th{font-size:12px;text-transform:uppercase;color:var(--muted);background:var(--surface-2)}
.modal{backdrop-filter:blur(8px)}
@media(max-width:900px){.grid,.cards{grid-template-columns:repeat(2,minmax(0,1fr))}.featured{grid-template-columns:1fr}.featured img{min-height:260px}.admin-shell{grid-template-columns:1fr}.admin-sidebar{position:static}.stats-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.main-nav{display:none;position:absolute;left:16px;right:16px;top:70px;padding:12px;background:var(--surface);border:1px solid var(--border);border-radius:16px;box-shadow:var(--shadow);flex-direction:column;align-items:stretch}.main-nav.open{display:flex}.main-nav>a{text-align:left}.menu-btn{display:block}}
@media(max-width:620px){.container{width:min(100% - 22px,1180px)}.grid,.cards,.form-grid,.stats-grid{grid-template-columns:1fr}.hero{padding:60px 0}.hero h1{letter-spacing:-1px}.page{padding-top:28px}.section{align-items:flex-start;flex-direction:column}.footer-grid{grid-template-columns:1fr}.featured-body{padding:24px}.admin-title{align-items:flex-start;flex-direction:column}}
/* dark mode */
body.dark{--bg:#0b1020;--surface:#111827;--surface-2:#172033;--text:#edf2f7;--muted:#9aa6b8;--border:#263246;--shadow:0 18px 55px rgba(0,0,0,.25)}
body.dark .site-header{background:rgba(11,16,32,.86)}
body.dark .hero{background:linear-gradient(135deg,#0f172a,#15102a)}
body.dark .alert-success{background:#052e1a;color:#bbf7d0;border-color:#14532d}
body.dark .alert-error{background:#3a1115;color:#fecaca;border-color:#7f1d1d}
::selection{background:rgba(99,91,255,.22)}