:root{
  --ink:#1b2a3a;
  --muted:#5a6878;
  --paper:#fbf8f1;
  --card:#ffffff;
  --line:#e9e2d3;
  --blue:#1f4e79;
  --blue-soft:#e8f0f8;
  --green:#2f6b55;
  --green-soft:#e6f2ec;
  --amber:#b7791f;
  --zalo:#0068ff;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{
  margin:0;font-family:"Be Vietnam Pro",system-ui,sans-serif;color:var(--ink);
  background:var(--paper);
  background-image:
    linear-gradient(var(--line) 1px,transparent 1px),
    linear-gradient(90deg,var(--line) 1px,transparent 1px);
  background-size:26px 26px;
  line-height:1.7;font-size:17px;
}
img{max-width:100%;height:auto;display:block}
a{color:var(--blue)}
.wrap{max-width:980px;margin:0 auto;padding:0 16px}
.narrow{max-width:740px}
.hand{font-family:"Patrick Hand",cursive}

/* Thanh menu */
.topbar{background:#fff;border-bottom:1px solid var(--line);position:sticky;top:0;z-index:10}
.topbar .wrap{display:flex;align-items:center;justify-content:space-between;gap:12px;min-height:60px;flex-wrap:wrap}
.brand{font-weight:800;color:var(--blue);text-decoration:none;font-size:18px;white-space:nowrap}
.brand small{display:block;font-weight:500;font-size:12px;color:var(--muted);line-height:1.2}
nav.menu{display:flex;gap:4px;flex-wrap:wrap}
nav.menu a{text-decoration:none;color:var(--ink);font-size:15px;padding:6px 10px;border-radius:8px;white-space:nowrap}
nav.menu a:hover{background:var(--blue-soft)}
nav.menu a[aria-current="page"]{background:var(--blue);color:#fff}
@media (max-width:720px){
  .topbar .wrap{padding-top:8px;padding-bottom:8px}
  nav.menu{width:100%;overflow-x:auto;flex-wrap:nowrap;padding-bottom:4px}
}

/* Đầu trang */
.hero{background:var(--blue);color:#fff;position:relative;overflow:hidden}
.hero::after{
  content:"a² + b² = c²   ·   2x + 3 = 11   ·   ½ + ⅓ = ⅚   ·   (x + 1)² = x² + 2x + 1   ·   AI soạn, thầy duyệt";
  position:absolute;left:-20px;right:-20px;bottom:10px;white-space:nowrap;
  font-family:"Patrick Hand",cursive;font-size:22px;opacity:.12;letter-spacing:2px;
}
.hero .wrap{display:grid;gap:28px;padding-top:44px;padding-bottom:60px;align-items:center}
@media (min-width:760px){.hero .wrap{grid-template-columns:260px 1fr;gap:44px}}
.hero .photo{width:230px;margin:0 auto;border-radius:18px;overflow:hidden;border:6px solid #fff;
  box-shadow:0 14px 34px rgba(0,0,0,.28);transform:rotate(-2deg)}
.tag{display:inline-block;background:rgba(255,255,255,.14);border:1px solid rgba(255,255,255,.3);
  padding:4px 12px;border-radius:999px;font-size:14px;margin-bottom:12px}
.hero h1{font-size:34px;line-height:1.2;margin:0 0 12px;font-weight:800}
.hero h1 span{display:block;font-size:20px;font-weight:500;opacity:.92;margin-top:8px}
.hero p.lead{font-size:18px;margin:0 0 22px;opacity:.95}
.page-hero .wrap{grid-template-columns:1fr !important;padding-top:36px;padding-bottom:46px}
.page-hero h1{font-size:30px}

/* Nút */
.btns{display:flex;flex-wrap:wrap;gap:10px}
.btn{display:inline-flex;align-items:center;gap:8px;padding:12px 18px;border-radius:12px;
  font-weight:700;text-decoration:none;font-size:16px;line-height:1.3}
.btn-white{background:#fff;color:var(--blue)}
.btn-line{background:transparent;color:#fff;border:1.5px solid rgba(255,255,255,.6)}
.btn-blue{background:var(--blue);color:#fff}
.btn-zalo{background:var(--zalo);color:#fff}
.btn-green{background:var(--green);color:#fff}
.btn-ghost{background:#fff;color:var(--blue);border:1.5px solid var(--blue)}

/* Con số */
.stats{display:grid;grid-template-columns:repeat(3,1fr);gap:10px;margin-top:-30px;position:relative}
.stat{background:#fff;border-radius:14px;padding:14px 10px;text-align:center;box-shadow:0 6px 18px rgba(27,42,58,.1)}
.stat b{display:block;font-size:24px;color:var(--blue);line-height:1.15}
.stat small{color:var(--muted);font-size:13px;line-height:1.35;display:block;margin-top:4px}

/* Khối nội dung */
section{padding:44px 0}
h2{font-size:26px;line-height:1.3;margin:0 0 14px;color:var(--blue)}
h3{font-size:19px;margin:0 0 6px}
.kicker{font-size:14px;font-weight:700;letter-spacing:.06em;text-transform:uppercase;color:var(--amber);margin:0 0 6px}
.card{background:var(--card);border:1px solid var(--line);border-radius:16px;padding:22px}
.grid2{display:grid;gap:16px}
@media (min-width:720px){.grid2{grid-template-columns:1fr 1fr}}
.door{display:flex;flex-direction:column;gap:8px}
.door .who{font-size:13px;font-weight:700;text-transform:uppercase;letter-spacing:.06em}
.door.parent .who{color:var(--blue)}
.door.teacher .who{color:var(--green)}
.door p{margin:0 0 8px;color:var(--muted)}
.door .btn{align-self:flex-start;margin-top:auto}

.steps{list-style:none;margin:0;padding:0;display:grid;gap:12px}
.steps li{background:#fff;border:1px solid var(--line);border-radius:14px;padding:16px 18px 16px 64px;position:relative}
.steps li::before{counter-increment:s;content:counter(s);position:absolute;left:18px;top:16px;
  width:32px;height:32px;border-radius:50%;background:var(--blue-soft);color:var(--blue);
  font-weight:800;display:grid;place-items:center}
.steps{counter-reset:s}
.steps.green li::before{background:var(--green-soft);color:var(--green)}
.steps p{margin:0;color:var(--muted)}

blockquote.say{margin:0;background:#fff;border-left:5px solid var(--amber);border-radius:0 14px 14px 0;
  padding:18px 22px;font-family:"Patrick Hand",cursive;font-size:26px;line-height:1.35;color:var(--ink)}
blockquote.say cite{display:block;font-family:"Be Vietnam Pro",sans-serif;font-style:normal;font-size:14px;color:var(--muted);margin-top:8px}

.honest{background:#fff8e8;border:1px dashed var(--amber);border-radius:14px;padding:18px 20px}
.honest b{color:var(--amber)}

.timeline{border-left:3px solid var(--blue-soft);margin-left:8px;padding-left:22px;display:grid;gap:26px}
.timeline .item{position:relative}
.timeline .item::before{content:"";position:absolute;left:-31px;top:8px;width:15px;height:15px;border-radius:50%;
  background:#fff;border:3px solid var(--blue)}
.timeline .when{font-size:13px;font-weight:700;color:var(--amber);text-transform:uppercase;letter-spacing:.05em}
.timeline p{margin:4px 0 0}

.contact-list{list-style:none;padding:0;margin:0;display:grid;gap:10px}
.contact-list li{background:#fff;border:1px solid var(--line);border-radius:12px;padding:14px 16px;display:flex;
  justify-content:space-between;gap:12px;flex-wrap:wrap;align-items:center}
.contact-list span{color:var(--muted);font-size:14px}
.contact-list a{font-weight:700;text-decoration:none;word-break:break-all}

.cta{background:var(--blue);color:#fff;border-radius:18px;padding:28px 24px}
.cta h2{color:#fff}
.cta p{opacity:.92}

footer{background:#16324d;color:#cdd8e3;padding:28px 0;font-size:14px}
footer .wrap{display:flex;flex-wrap:wrap;gap:12px;justify-content:space-between}
footer a{color:#fff}
.muted{color:var(--muted)}
p.big{font-size:19px}