:root {
  --navy: #1d2b5a; --navy-2: #2c3f7c; --gold: #e7a922; --gold-2: #f6c453;
  --bg: #fffaf0; --card: #ffffff; --ink: #1b2236; --muted: #667089; --line: #ece3cf;
  --ok: #1e8e4e; --bad: #c0392b; --radius: 18px;
}
* { box-sizing: border-box; }
body { margin: 0; font-family: "Be Vietnam Pro", system-ui, sans-serif; background: var(--bg); color: var(--ink); line-height: 1.55; }
a { color: inherit; }
main { max-width: 1120px; margin: 0 auto; padding: 0 16px 40px; }

.top { position: sticky; top: 0; z-index: 10; display: flex; justify-content: space-between; align-items: center;
  gap: 12px; padding: 10px 16px; background: var(--navy); color: #fff; }
.brand { font-weight: 800; font-size: 1.15rem; text-decoration: none; display: flex; align-items: center; gap: 8px; }
.account { display: flex; align-items: center; gap: 8px; font-size: .9rem; flex-wrap: wrap; justify-content: flex-end; }
.account .pill { background: rgba(255,255,255,.14); padding: 4px 10px; border-radius: 99px; }

.btn { display: inline-block; border: 0; cursor: pointer; font: inherit; font-weight: 700; padding: 10px 18px;
  border-radius: 99px; background: var(--navy); color: #fff; text-decoration: none; }
.btn.gold { background: var(--gold); color: var(--navy); }
.btn.ghost { background: transparent; border: 2px solid currentColor; padding: 6px 14px; }
.btn.big { font-size: 1.15rem; padding: 14px 34px; }
.btn:disabled { opacity: .55; cursor: wait; }

.hero { display: grid; grid-template-columns: 1fr 1.1fr; gap: 28px; align-items: center; padding: 36px 0 24px; }
.eyebrow { color: var(--gold); font-weight: 700; text-transform: uppercase; letter-spacing: .08em; margin: 0; }
.hero h1 { font-size: clamp(2.4rem, 6vw, 4rem); line-height: 1.05; margin: 8px 0 12px; color: var(--navy); }
.lead { font-size: 1.1rem; color: var(--muted); max-width: 30em; }
.hero-art svg { width: 100%; height: auto; display: block; filter: drop-shadow(0 12px 30px rgba(29,43,90,.15)); }

.grades { padding: 12px 0; }
.level h2 { color: var(--navy); margin: 22px 0 10px; font-size: 1.25rem; }
.grade-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(150px, 1fr)); gap: 12px; }
.grade { border: 0; cursor: pointer; font: inherit; text-align: left; padding: 18px; border-radius: var(--radius);
  background: var(--card); box-shadow: 0 2px 0 var(--line), 0 6px 18px rgba(29,43,90,.07); transition: transform .15s; }
.grade:hover { transform: translateY(-3px); }
.grade b { display: block; font-size: 1.6rem; color: var(--navy); }
.grade small { color: var(--muted); }
.grade[data-level="1"] { border-top: 5px solid #f39c12; }
.grade[data-level="2"] { border-top: 5px solid #2e86de; }
.grade[data-level="3"] { border-top: 5px solid #8e44ad; }

.how { margin-top: 30px; background: var(--navy); color: #fff; border-radius: 24px; padding: 26px; }
.how h2 { margin-top: 0; }
.how-list { list-style: none; padding: 0; display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 10px; }
.how-list li { background: rgba(255,255,255,.08); border-radius: 14px; padding: 12px; display: flex; gap: 10px; align-items: center; }
.how-list b, .num { display: inline-grid; place-items: center; min-width: 30px; height: 30px; border-radius: 50%;
  background: var(--gold); color: var(--navy); font-weight: 800; }
.hero > * { min-width: 0; }
.price-title { margin: 20px 0 0; font-weight: 700; color: var(--navy); }
.prices { display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; margin-top: 8px; max-width: 30em; }
.prices div { background: #fff; color: var(--navy); border-radius: 14px; padding: 12px; text-align: center; position: relative;
  box-shadow: 0 2px 0 var(--line), 0 6px 18px rgba(29,43,90,.07); }
.prices span { display: block; font-size: 1.3rem; font-weight: 800; }
.prices .best { outline: 3px solid var(--gold); }
.prices em { font-size: .75rem; font-style: normal; color: var(--bad); font-weight: 700; }

.crumb { margin: 18px 0 4px; color: var(--muted); font-size: .9rem; }
.study-title { color: var(--navy); margin: 4px 0 14px; }
.topics { background: var(--card); border-radius: var(--radius); padding: 12px 18px; border: 1px solid var(--line); }
.topics summary { font-weight: 700; cursor: pointer; color: var(--navy); }
.topics ol { margin: 10px 0 4px; columns: 2 280px; column-gap: 30px; }
.topics li { margin-bottom: 4px; break-inside: avoid; }

.windows { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; margin-top: 16px; }
.win { background: var(--card); border-radius: var(--radius); border: 1px solid var(--line); overflow: hidden; display: flex; flex-direction: column; min-height: 260px; }
.win-wide { grid-column: 1 / -1; }
.win > header { background: #fdf3dc; padding: 10px 14px; font-weight: 700; color: var(--navy); display: flex; gap: 10px; align-items: center; }
.drop { margin: 12px; flex: 1; min-height: 180px; border: 2px dashed #d9c9a3; border-radius: 14px; display: grid; place-items: center;
  cursor: pointer; position: relative; overflow: hidden; background: #fffdf7; }
.drop img { width: 100%; height: 100%; max-height: 360px; object-fit: contain; }
.drop img:not([hidden]) + .drop-hint { position: absolute; bottom: 8px; background: rgba(29,43,90,.8); color: #fff; padding: 4px 10px; border-radius: 99px; font-size: .8rem; }
.drop-hint { color: var(--muted); text-align: center; padding: 10px; }
.out { padding: 4px 16px 14px; word-break: break-word; }
.out p, .out li { white-space: pre-wrap; }
.out:empty { display: none; }
.out h4 { margin: 12px 0 4px; color: var(--navy); }
.out ul, .out ol { margin: 4px 0; padding-left: 20px; }
.muted { color: var(--muted); }
.good { color: var(--ok); } .wrong { color: var(--bad); }
.score { display: inline-block; background: var(--gold); color: var(--navy); font-weight: 800; padding: 2px 12px; border-radius: 99px; }
.way { border-left: 4px solid var(--gold); padding-left: 12px; margin: 10px 0; }
.answer { background: #eef7f1; border-radius: 10px; padding: 6px 10px; font-weight: 700; color: var(--ok); }
.way details summary { cursor: pointer; color: var(--navy); font-weight: 600; }
.solve-bar { text-align: center; margin: 20px 0; }
.loading { display: inline-block; width: 18px; height: 18px; border: 3px solid var(--line); border-top-color: var(--gold); border-radius: 50%; animation: spin 1s linear infinite; vertical-align: middle; }
@keyframes spin { to { transform: rotate(360deg); } }

.dlg { border: 0; border-radius: 22px; padding: 24px; width: min(460px, calc(100vw - 32px)); max-height: calc(100vh - 40px); box-shadow: 0 20px 60px rgba(0,0,0,.25); }
.dlg::backdrop { background: rgba(20,26,50,.55); }
.dlg h2 { margin-top: 0; color: var(--navy); }
.x { position: absolute; right: 12px; top: 8px; border: 0; background: none; font-size: 1.8rem; cursor: pointer; color: var(--muted); }
.subjects { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
.subjects button { border: 1px solid var(--line); background: #fffdf7; border-radius: 14px; padding: 14px 10px; font: inherit; font-weight: 700; cursor: pointer; color: var(--navy); }
.subjects button:hover { background: #fdf3dc; }
.subjects .ic { font-size: 1.6rem; display: block; }

.field { display: block; margin: 12px 0; }
.field span { display: block; font-weight: 600; margin-bottom: 4px; }
.field input, .field select { width: 100%; font: inherit; padding: 12px 14px; border-radius: 12px; border: 1.5px solid #d8d2c2; }
.field input:focus, .field select:focus { outline: 2px solid var(--gold); border-color: transparent; }
.otp-input { letter-spacing: .5em; font-size: 1.4rem !important; text-align: center; }
.demo { background: #fff4d6; border-radius: 10px; padding: 8px 12px; font-size: .9rem; }
.plans { display: grid; gap: 8px; margin: 10px 0; }
.plan { display: flex; justify-content: space-between; align-items: center; border: 2px solid var(--line); border-radius: 14px; padding: 12px 16px;
  background: #fff; font: inherit; cursor: pointer; text-align: left; }
.plan:hover, .plan.on { border-color: var(--gold); background: #fffaf0; }
.plan b { color: var(--navy); } .plan span { font-weight: 800; color: var(--bad); }
.tabs { display: flex; gap: 6px; margin: 10px 0; }
.tabs button { flex: 1; border: 2px solid var(--line); background: #fff; border-radius: 10px; padding: 8px; font: inherit; font-weight: 700; cursor: pointer; }
.tabs button.on { border-color: var(--navy); background: var(--navy); color: #fff; }
.qr { display: grid; place-items: center; padding: 10px; background: #fff; border-radius: 14px; border: 1px solid var(--line); }
.qr img, .qr canvas { max-width: 220px; height: auto; }
.payinfo { font-size: .95rem; margin: 10px 0; }
.payinfo div { display: flex; justify-content: space-between; border-bottom: 1px dashed var(--line); padding: 4px 0; gap: 10px; }
.payinfo b { color: var(--navy); text-align: right; }
.success { text-align: center; }
.success .big-ic { font-size: 3rem; }
.row { display: flex; gap: 8px; margin-top: 12px; }
.row .btn { flex: 1; }
.err { color: var(--bad); font-weight: 600; min-height: 1.2em; }

.toast { position: fixed; left: 50%; top: 18px; transform: translate(-50%, -150%); background: var(--bad); color: #fff; font-weight: 700;
  padding: 12px 20px; border-radius: 14px; box-shadow: 0 10px 30px rgba(0,0,0,.25); transition: transform .3s; z-index: 100; max-width: calc(100vw - 32px); }
.toast.show { transform: translate(-50%, 0); }
.toast.ok { background: var(--ok); }
.foot { text-align: center; color: var(--muted); padding: 20px; font-size: .9rem; }

@media (max-width: 760px) {
  .hero { grid-template-columns: 1fr; padding-top: 20px; }
  .windows { grid-template-columns: 1fr; }
  .brand { font-size: 1rem; white-space: nowrap; }
  .top { flex-wrap: wrap; }
  .account { flex: 1 1 100%; justify-content: flex-start; font-size: .82rem; }
  .account:has(#loginBtn) { flex: 0 0 auto; }
  .account .btn { padding: 6px 12px; }
  .prices { gap: 6px; }
  .prices div { padding: 10px 4px; min-width: 0; }
  .prices span { font-size: 1.05rem; }
  .prices em { font-size: .68rem; }
}