:root{
  /* nen trang, tong xanh nuoc bien */
  --bg:#ffffff; --bg2:#f7fafd; --bg3:#eaf2fa; --line:#e2eaf2;
  --ink:#0d2b45; --ink2:#4c6885; --ink3:#8199b0;
  --acc:#0d6fc4; --acc2:#1385e2; --deep:#083a63;
  --ok:#0e8a5f; --warn:#b5730a; --err:#c62f36; --link:#0d6fc4;
  --r:12px; --shadow:0 1px 3px rgba(13,43,69,.05);
  --wrap:1500px;
  --bar:56px;      /* chieu cao thanh tren */
  --side:240px;    /* be ngang menu trai */
}
*{box-sizing:border-box}
html,body{margin:0;padding:0}
body{
  background:var(--bg); color:var(--ink);
  font:15px/1.6 "Roboto",-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif;
  -webkit-font-smoothing:antialiased;
  padding-top:var(--bar);
}
a{color:var(--link);text-decoration:none}
a:hover{text-decoration:underline}
img,video{max-width:100%;display:block}
h1,h2,h3,h4{line-height:1.25;margin:0 0 .5em;color:var(--deep)}
h1{font-size:26px;letter-spacing:-.02em;font-weight:700}
h2{font-size:20px;font-weight:700}
h3{font-size:16px;font-weight:700}
p{margin:0 0 1em}
small,.small{font-size:13px;color:var(--ink2)}
.muted{color:var(--ink2)}
.wrap{max-width:var(--wrap);margin:0 auto;padding:0 24px}
.narrow{max-width:760px}
.mono{font-family:ui-monospace,SFMono-Regular,Consolas,monospace;font-size:13px}

/* ============ THANH TREN (kieu YouTube) ============ */
.topbar{
  position:fixed;top:0;left:0;right:0;height:var(--bar);z-index:70;
  display:flex;align-items:center;gap:10px;padding:0 16px;
  background:#fff;border-bottom:1px solid var(--line);
}
.logo{display:flex;align-items:center;gap:6px;font-weight:800;font-size:19px;color:var(--deep);
  letter-spacing:-.03em;white-space:nowrap;margin-right:8px}
.logo:hover{text-decoration:none}
.logo b{color:var(--acc);font-weight:800}
.logo .mark{display:inline-flex;align-items:center;justify-content:center;width:26px;height:19px;
  background:var(--acc);color:#fff;border-radius:6px;font-size:10px;padding-left:1px}

/* nut tron chi co bieu tuong */
.iconbtn{display:inline-flex;align-items:center;justify-content:center;position:relative;
  width:38px;height:38px;border-radius:50%;border:none;background:none;cursor:pointer;
  color:var(--ink);flex:none;padding:0}
.iconbtn:hover{background:var(--bg3);text-decoration:none}
.iconbtn svg{width:22px;height:22px}
.iconbtn b{position:absolute;top:2px;right:1px;background:var(--err);color:#fff;font-size:10px;
  font-weight:700;line-height:1;padding:2px 4px;border-radius:9px;min-width:15px;text-align:center}
svg{fill:none;stroke:currentColor;stroke-width:1.7;stroke-linecap:round;stroke-linejoin:round;
  width:24px;height:24px;display:block}

/* o tim kiem dai o giua */
.searchbar{flex:1;max-width:620px;margin:0 auto;display:flex;min-width:0}
.searchbar input{flex:1;min-width:0;height:38px;border:1px solid var(--line);border-right:none;
  border-radius:19px 0 0 19px;padding:0 8px 0 16px;font-size:14.5px;background:#fff;color:var(--ink)}
.searchbar input:focus{outline:none;border-color:var(--acc);box-shadow:none}
.searchbar button{width:62px;height:38px;flex:none;border:1px solid var(--line);border-radius:0 19px 19px 0;
  background:var(--bg2);color:var(--ink2);cursor:pointer;display:flex;align-items:center;justify-content:center}
.searchbar button:hover{background:var(--bg3);color:var(--acc)}
.searchgo{display:none}

.topright{display:flex;align-items:center;gap:8px;flex:none;margin-left:auto}

/* ============ MENU TRAI (kieu YouTube) ============ */
.side{
  position:fixed;top:var(--bar);left:0;bottom:0;width:var(--side);z-index:60;
  background:#fff;border-right:1px solid var(--line);
  overflow-y:auto;overscroll-behavior:contain;padding:10px 0 24px;
  transition:transform .16s ease;
}
.side::-webkit-scrollbar{width:8px}
.side::-webkit-scrollbar-thumb{background:#d6e2ee;border-radius:8px}
/* ⭐ Ong chu 23/08: "menu cho nho hon, sat nhau hon, chu khong can bold
   cho menu no thu lai chut" — menu GON LAI.
   ⛔ Nho vua phai: van phai bam trung duoc bang chuot, va tieu de nhom van
      phai phan biet duoc voi muc con. */
.side a{display:flex;align-items:center;gap:11px;height:32px;margin:0 8px;padding:0 10px;
  border-radius:8px;color:var(--ink);font-size:13px;font-weight:400;white-space:nowrap;overflow:hidden}
.side a:hover{background:var(--bg3);text-decoration:none;color:var(--ink)}
.side a.on{background:var(--bg3);color:var(--acc);font-weight:600}
.side a i{flex:none;display:flex;color:var(--ink2)}
.side a i svg{width:18px;height:18px}
.side a.on i{color:var(--acc)}
.side a span{overflow:hidden;text-overflow:ellipsis}
.side a .cnt{background:var(--acc);color:#fff;border-radius:9px;padding:1px 6px;font-size:11px;margin-left:4px}
.side .grp{font-size:10.5px;font-weight:700;text-transform:uppercase;letter-spacing:.06em;
  color:var(--ink3);padding:11px 18px 4px}
.side hr{border:none;border-top:1px solid var(--line);margin:7px 14px}
.sidefoot{padding:18px 20px 4px;font-size:11.5px;color:var(--ink3)}
.scrim{display:none;position:fixed;inset:var(--bar) 0 0 0;background:rgba(8,32,55,.42);z-index:55}

.main{margin-left:var(--side);min-height:calc(100vh - var(--bar))}

/* thu menu lai tren may tinh */
body.side-off .side{transform:translateX(-100%)}
body.side-off .main{margin-left:0}

@media(max-width:999px){
  .side{transform:translateX(-100%);box-shadow:0 8px 30px rgba(8,32,55,.16)}
  .main{margin-left:0}
  body.side-open .side{transform:none}
  body.side-open .scrim{display:block}
  body.side-off .side{transform:translateX(-100%)}
}

/* ---------- buttons ---------- */
.btn{display:inline-flex;align-items:center;gap:7px;justify-content:center;
  background:var(--acc);color:#fff;border:1px solid transparent;border-radius:20px;
  padding:9px 17px;font-size:14px;font-weight:600;cursor:pointer;font-family:inherit;line-height:1.3}
.btn:hover{background:var(--acc2);text-decoration:none;color:#fff}
.btn.ghost{background:#fff;border-color:var(--line);color:var(--deep)}
.btn.ghost:hover{background:var(--bg3);color:var(--acc);border-color:#c4dcf1}
.btn.sm{padding:6px 13px;font-size:13px}
.btn.lg{padding:12px 26px;font-size:15.5px}
.btn.danger{background:var(--err)}
.btn.ok{background:var(--ok)}
.btn:disabled{opacity:.45;cursor:not-allowed}
.btnrow{display:flex;gap:10px;flex-wrap:wrap;align-items:center}

/* nut doi ngon ngu */
.langsw{display:inline-flex;border:1px solid var(--line);border-radius:20px;overflow:hidden;background:#fff}
.langsw a{padding:6px 11px;font-size:12px;font-weight:700;color:var(--ink2);line-height:1.2;
  border-right:1px solid var(--line)}
.langsw a:last-child{border-right:none}
.langsw a:hover{background:var(--bg3);color:var(--acc);text-decoration:none}
.langsw a.on{background:var(--acc);color:#fff}

/* ---------- cards / panels ---------- */
.card{background:#fff;border:1px solid var(--line);border-radius:var(--r);padding:20px;margin-bottom:18px;
  box-shadow:var(--shadow)}
.card.pad0{padding:0;overflow:hidden}
.grid{display:grid;gap:16px}
.g2{grid-template-columns:repeat(auto-fit,minmax(280px,1fr))}
.g3{grid-template-columns:repeat(4,1fr);row-gap:28px}
@media(max-width:1250px){.g3{grid-template-columns:repeat(3,1fr)}}
@media(max-width:820px){.g3{grid-template-columns:repeat(2,1fr)}}
@media(max-width:460px){.g3{grid-template-columns:1fr}}
.g4{grid-template-columns:repeat(auto-fit,minmax(190px,1fr))}
/* 8 o danh muc = 2 hang x 4, luon day, khong o nao le xuong */
.cats{display:grid;grid-template-columns:repeat(4,1fr);gap:16px}
.cats > a{margin:0;text-align:center}
@media(max-width:900px){.cats{grid-template-columns:repeat(2,1fr)}}
@media(max-width:480px){.cats{grid-template-columns:1fr}}
.split{display:grid;grid-template-columns:2fr 1fr;gap:22px;align-items:start}
@media(max-width:1100px){.split{grid-template-columns:1fr}}

/* ---------- the video kieu YouTube: khong vien, anh bo goc ---------- */
.tile{background:none;border:none;border-radius:0;overflow:visible;display:block;color:inherit;box-shadow:none}
.tile:hover{text-decoration:none}
.tile .shot{aspect-ratio:16/9;background:#e6eef6 center/cover no-repeat;position:relative;
  border-radius:var(--r);overflow:hidden;transition:border-radius .12s}
.tile:hover .shot{border-radius:4px}
.tile .dur{position:absolute;right:6px;bottom:6px;background:rgba(6,25,42,.82);color:#fff;
  font-size:12px;padding:1px 5px;border-radius:5px;font-weight:600;letter-spacing:.01em}
.tile .body{padding:10px 2px 0}
.tile .t{font-weight:600;font-size:14.5px;line-height:1.35;color:var(--deep);display:-webkit-box;
  -webkit-line-clamp:2;-webkit-box-orient:vertical;overflow:hidden;margin-bottom:3px}
.tile:hover .t{color:var(--acc)}
.tile .m{font-size:12.5px;color:var(--ink3);line-height:1.5}

/* ---------- forms ---------- */
label{display:block;font-size:13px;font-weight:600;color:var(--ink2);margin:0 0 5px}
input[type=text],input[type=email],input[type=password],input[type=tel],input[type=url],
input[type=number],input[type=date],input[type=search],select,textarea{
  width:100%;background:#fff;border:1px solid var(--line);border-radius:8px;
  color:var(--ink);padding:10px 12px;font:inherit;font-size:14px}
textarea{min-height:110px;resize:vertical}
input:focus,select:focus,textarea:focus{outline:none;border-color:var(--acc);
  box-shadow:0 0 0 3px rgba(13,111,196,.12)}
input[type=file]{width:100%;background:var(--bg2);border:1px dashed #b9d0e4;border-radius:8px;padding:14px;
  color:var(--ink2);font-size:14px}
.field{margin-bottom:16px}
.row{display:grid;grid-template-columns:1fr 1fr;gap:14px}
@media(max-width:640px){.row{grid-template-columns:1fr}}
.check{display:flex;gap:10px;align-items:flex-start;margin-bottom:11px;font-size:14px;color:var(--ink);
  font-weight:400;line-height:1.5}
.check input{margin-top:3px;flex:none;width:16px;height:16px;accent-color:var(--acc)}
fieldset{border:1px solid var(--line);border-radius:var(--r);padding:16px 18px;margin:0 0 18px;background:#fff}
legend{font-size:12px;font-weight:700;text-transform:uppercase;letter-spacing:.06em;color:var(--acc);padding:0 7px}
.hint{font-size:12.5px;color:var(--ink3);margin-top:5px}

/* ---------- tables ---------- */
table{width:100%;border-collapse:collapse;font-size:14px}
th{text-align:left;font-size:11px;text-transform:uppercase;letter-spacing:.06em;color:var(--ink3);
  padding:10px 12px;border-bottom:1px solid var(--line);white-space:nowrap;font-weight:700}
td{padding:11px 12px;border-bottom:1px solid var(--line);vertical-align:middle}
tr:last-child td{border-bottom:none}
tbody tr:hover{background:var(--bg2)}
.tscroll{overflow-x:auto}
.num{text-align:right;font-variant-numeric:tabular-nums}

/* ---------- misc ---------- */
.tag{display:inline-block;font-size:11px;font-weight:700;text-transform:uppercase;letter-spacing:.05em;
  padding:3px 8px;border-radius:20px;background:var(--bg3);color:var(--ink2);border:1px solid var(--line)}
.tag.ok{background:#e4f6ee;color:#0b7350;border-color:#b9e5d3}
.tag.warn{background:#fdf3e0;color:#96600a;border-color:#f0dcb4}
.tag.err{background:#fdeaea;color:#b3282f;border-color:#f4c9cb}
.tag.acc{background:#e5f1fb;color:var(--acc);border-color:#bcdcf5}
.flash{padding:12px 16px;border-radius:var(--r);margin-bottom:18px;font-size:14px;font-weight:500}
.flash.ok{background:#e4f6ee;border:1px solid #b9e5d3;color:#0b6d4c}
.flash.err{background:#fdeaea;border:1px solid #f4c9cb;color:#a32229}
.errbox{background:#fdeaea;border:1px solid #f4c9cb;border-radius:var(--r);padding:14px 18px;margin-bottom:18px}
.errbox ul{margin:0;padding-left:20px}
.errbox li{color:#a32229;margin-bottom:4px}
.stat{background:#fff;border:1px solid var(--line);border-radius:var(--r);padding:16px 18px;box-shadow:var(--shadow)}
.stat:hover{border-color:#c4dcf1}
.stat .k{font-size:11.5px;text-transform:uppercase;letter-spacing:.06em;color:var(--ink3);font-weight:700}
.stat .v{font-size:26px;font-weight:800;letter-spacing:-.02em;margin-top:5px;color:var(--deep)}
.stat .v.acc{color:var(--acc)}
.stat .v.ok{color:var(--ok)}
pre.doc{white-space:pre-wrap;font:13px/1.75 ui-monospace,Consolas,monospace;color:var(--ink2);
  background:var(--bg2);border:1px solid var(--line);border-radius:var(--r);padding:20px;overflow-x:auto}
hr{border:none;border-top:1px solid var(--line);margin:24px 0}

/* the loc kieu YouTube */
.pill{display:inline-flex;gap:6px;align-items:center;padding:7px 14px;border-radius:9px;background:var(--bg3);
  border:1px solid transparent;color:var(--deep);font-size:13.5px;font-weight:600;white-space:nowrap}
.pill.on{background:var(--deep);border-color:var(--deep);color:#fff}
.pill:hover{text-decoration:none;background:#dbe8f5;color:var(--deep)}
.pill.on:hover{color:#fff;background:var(--deep)}
.pills{display:flex;gap:9px;flex-wrap:nowrap;overflow-x:auto;margin-bottom:20px;padding-bottom:2px;
  scrollbar-width:none}
.pills::-webkit-scrollbar{display:none}

/* ---------- hero ---------- */
.hero{padding:56px 0 44px;text-align:center;border-bottom:1px solid var(--line);
  background:linear-gradient(180deg,#eef6fd 0%,#ffffff 100%)}
.hero h1{font-size:42px;font-weight:800;letter-spacing:-.03em;margin-bottom:14px;color:var(--deep)}
.hero p{font-size:17px;color:var(--ink2);max-width:620px;margin:0 auto 26px}
@media(max-width:640px){.hero h1{font-size:29px}}
.trust{display:flex;gap:44px;justify-content:center;flex-wrap:wrap;margin-top:38px}
.trust div{text-align:center}
.trust .n{font-size:27px;font-weight:800;color:var(--acc)}
.trust .l{font-size:12px;text-transform:uppercase;letter-spacing:.07em;color:var(--ink3);font-weight:700}

.steps{counter-reset:s;display:grid;gap:16px;grid-template-columns:repeat(auto-fit,minmax(230px,1fr))}
.steps > div{background:#fff;border:1px solid var(--line);border-radius:var(--r);padding:20px;position:relative;
  box-shadow:var(--shadow)}
.steps > div::before{counter-increment:s;content:counter(s);display:flex;align-items:center;justify-content:center;
  width:30px;height:30px;border-radius:50%;background:var(--acc);color:#fff;font-weight:800;font-size:14px;
  margin-bottom:12px}

.foot{border-top:1px solid var(--line);margin-top:48px;padding:30px 0;color:var(--ink3);font-size:13px;
  background:var(--bg2)}
.foot a{color:var(--ink2);margin-right:18px;display:inline-block;margin-bottom:6px}
/* chi dat le tren/duoi — de nguyen le hai ben cua .wrap, khong thi noi dung dinh sat menu */
.section{padding-top:28px;padding-bottom:28px}
.sechead{display:flex;justify-content:space-between;align-items:baseline;margin-bottom:18px;gap:16px;flex-wrap:wrap}

/* ================= DIEN THOAI & MAY TINH BANG ================= */
@media(max-width:900px){
  .wrap{padding:0 16px}
  .topbar{gap:6px;padding:0 10px}
  .logo{font-size:17px}
  .section{padding-top:22px;padding-bottom:22px}
  .hero{padding:36px 0 30px}
  .hero p{font-size:16px}
  .trust{gap:22px;margin-top:26px}
  .trust > div{flex:1 1 90px}
  .trust .n{font-size:22px}
  .card{padding:16px}
  h1{font-size:23px}
  h2{font-size:18px}
  .hide-sm{display:none}
}
@media(max-width:700px){
  /* o tim kiem nhuong cho: doi thanh mot nut kinh lup */
  .searchbar{display:none}
  .searchgo{display:inline-flex}
  .langsw a{padding:5px 8px;font-size:11px}
}
@media(max-width:560px){
  .btn.lg{width:100%}
  .btnrow > .btn.lg{flex:1 1 100%}
  .sechead{gap:8px}
  .hero .btnrow{flex-direction:column}
  .foot a{margin-right:14px}
  table{font-size:13px}
  th,td{padding:9px 10px}
  fieldset{padding:14px}
  .logo{font-size:16px}
}

/* ---------- bang ty le: moi nguon MOT dong, MOT o ---------- */
.rateline{display:flex;gap:10px;align-items:center;padding:11px 0;
  border-bottom:1px solid var(--line);flex-wrap:wrap}
.ratebox > summary::-webkit-details-marker{display:none}
.ratebox[open] > .rateline{border-bottom-color:transparent}
.detail-link{font-size:12.5px;font-weight:600;color:var(--acc)}
.detail-link::after{content:' ▸'}
.ratebox[open] .detail-link::after{content:' ▾'}