:root {
    --bg: #f6f8fc;
    --surface: #ffffff;
    --surface-soft: #f1f5fb;
    --text: #17233b;
    --muted: #6e7a90;
    --primary: #2f6ee5;
    --primary-dark: #2459be;
    --border: #e4eaf3;
    --shadow: 0 16px 42px rgba(31, 54, 92, 0.10);
    --radius: 22px;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
    margin: 0;
    font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
    color: var(--text);
    background: var(--bg);
    line-height: 1.55;
}

a { color: inherit; }
.shell { width: min(1180px, calc(100% - 40px)); margin: 0 auto; }

.topbar {
    position: sticky;
    top: 0;
    z-index: 20;
    background: rgba(255,255,255,.92);
    border-bottom: 1px solid rgba(228,234,243,.9);
    backdrop-filter: blur(14px);
}
.nav-wrap {
    min-height: 76px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 30px;
}
.brand {
    display: inline-flex;
    align-items: center;
    gap: 12px;
    text-decoration: none;
}
.brand-mark {
    display: grid;
    place-items: center;
    width: 44px;
    height: 44px;
    border-radius: 14px;
    background: #eaf1ff;
    font-size: 24px;
}
.brand strong, .brand small { display: block; }
.brand strong { font-size: 17px; }
.brand small { color: var(--muted); font-size: 12px; margin-top: 1px; }
.nav { display: flex; align-items: center; gap: 22px; }
.nav a {
    text-decoration: none;
    color: #4d5a71;
    font-size: 14px;
    font-weight: 650;
    padding: 26px 0 24px;
    border-bottom: 2px solid transparent;
}
.nav a:hover, .nav a.active { color: var(--primary); border-color: var(--primary); }
.nav .teacher-link {
    padding: 10px 15px;
    border: 1px solid var(--border);
    border-radius: 12px;
    background: #fff;
}

.hero {
    overflow: hidden;
    background:
        radial-gradient(circle at 80% 20%, rgba(83, 145, 255, .16), transparent 26%),
        linear-gradient(180deg, #fff 0%, #f7faff 100%);
    border-bottom: 1px solid var(--border);
}
.hero-grid {
    min-height: 540px;
    display: grid;
    grid-template-columns: 1.05fr .95fr;
    gap: 64px;
    align-items: center;
    padding: 70px 0 76px;
}
.eyebrow, .section-kicker {
    display: inline-block;
    color: var(--primary);
    font-weight: 800;
    font-size: 12px;
    letter-spacing: .14em;
    text-transform: uppercase;
}
.hero h1 {
    margin: 14px 0 20px;
    font-size: clamp(46px, 6vw, 76px);
    line-height: .98;
    letter-spacing: -.045em;
}
.hero p {
    max-width: 680px;
    color: var(--muted);
    font-size: 18px;
    margin: 0 0 30px;
}
.hero-actions { display: flex; gap: 12px; flex-wrap: wrap; }
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 12px;
    min-height: 48px;
    padding: 0 19px;
    border-radius: 13px;
    font-weight: 750;
    text-decoration: none;
    transition: transform .18s ease, box-shadow .18s ease, background .18s ease;
}
.btn:hover { transform: translateY(-2px); }
.btn-primary {
    background: var(--primary);
    color: #fff;
    box-shadow: 0 12px 28px rgba(47,110,229,.25);
}
.btn-primary:hover { background: var(--primary-dark); }
.btn-secondary { background: #fff; border: 1px solid var(--border); color: #26334b; }

.hero-card { min-height: 370px; display: grid; place-items: center; }
.desk-card {
    position: relative;
    width: min(500px, 100%);
    height: 360px;
    border-radius: 30px;
    background: linear-gradient(145deg, #dfe9fa, #f6f9ff);
    box-shadow: var(--shadow);
    overflow: hidden;
    border: 1px solid #e3eaf5;
}
.desk-card::after {
    content: "";
    position: absolute;
    left: 0; right: 0; bottom: 0;
    height: 108px;
    background: linear-gradient(180deg, #b9845b, #a96f48);
}
.floating-paper { position: absolute; top: 42px; left: 56px; font-size: 32px; transform: rotate(-18deg); opacity: .7; }
.hero-note { position: absolute; right: 34px; top: 50px; font-size: 21px; line-height: 1.2; font-weight: 800; color: #4169a8; transform: rotate(-4deg); }
.books { position: absolute; left: 42px; bottom: 76px; z-index: 2; width: 190px; }
.book { height: 35px; display: flex; align-items: center; padding: 0 15px; font-size: 12px; font-weight: 900; letter-spacing: .06em; color: #fff; margin-top: 5px; border-radius: 6px; box-shadow: 0 5px 10px rgba(0,0,0,.12); }
.b1 { background: #4169a8; width: 150px; }
.b2 { background: #e09f3e; width: 180px; }
.b3 { background: #6d9f71; width: 165px; }
.laptop { position: absolute; right: 30px; bottom: 55px; z-index: 3; width: 220px; height: 145px; border-radius: 12px 12px 6px 6px; background: #cbd3df; padding: 10px; box-shadow: 0 10px 22px rgba(0,0,0,.18); }
.screen { height: 100%; background: #fff; border-radius: 5px; padding: 14px; }
.screen-dot { width: 7px; height: 7px; display: inline-block; border-radius: 50%; background: #cbd5e5; margin-right: 4px; }
.screen-line { height: 8px; width: 72%; background: #dae5f5; border-radius: 20px; margin-top: 18px; }
.screen-line.long { width: 90%; }
.screen-line.short { width: 55%; }
.plant { position: absolute; right: 18px; bottom: 155px; z-index: 4; font-size: 54px; filter: drop-shadow(0 6px 4px rgba(0,0,0,.12)); }

.section { padding: 74px 0; }
.section-soft { background: var(--surface-soft); border-top: 1px solid var(--border); }
.section-heading {
    display: flex;
    align-items: flex-end;
    justify-content: space-between;
    gap: 20px;
    margin-bottom: 28px;
}
.section-heading.compact { margin-bottom: 24px; }
.section-heading h2 { margin: 5px 0 0; font-size: 34px; letter-spacing: -.03em; }
.muted { color: var(--muted); font-size: 14px; }

.class-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; }
.class-card {
    position: relative;
    min-height: 185px;
    padding: 22px;
    border-radius: 20px;
    background: var(--surface);
    border: 1px solid var(--border);
    box-shadow: 0 10px 26px rgba(30, 49, 80, .05);
    text-decoration: none;
    transition: transform .18s ease, box-shadow .18s ease, border-color .18s ease;
}
.class-card:hover { transform: translateY(-3px); box-shadow: var(--shadow); }
.test-card { border-top: 4px solid var(--primary); }
.disabled-card { opacity: .6; cursor: default; }
.disabled-card:hover { transform: none; box-shadow: 0 10px 26px rgba(30, 49, 80, .05); }
.card-icon {
    width: 46px;
    height: 46px;
    display: grid;
    place-items: center;
    border-radius: 14px;
    background: #edf3ff;
    font-size: 24px;
    margin-bottom: 18px;
}
.class-card strong, .class-card span, .class-card small { display: block; }
.class-card strong { font-size: 22px; }
.class-card div > span { color: #536079; margin-top: 3px; font-weight: 650; }
.class-card small { color: #8792a7; margin-top: 5px; }
.circle-arrow {
    position: absolute;
    right: 18px;
    bottom: 18px;
    width: 36px;
    height: 36px;
    display: grid !important;
    place-items: center;
    border-radius: 50%;
    background: #edf3ff;
    color: var(--primary);
    font-weight: 900;
}

.feature-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; }
.feature-card {
    background: #fff;
    border: 1px solid var(--border);
    border-radius: 18px;
    padding: 24px;
}
.feature-icon { display: inline-grid; place-items: center; width: 44px; height: 44px; border-radius: 13px; background: #edf3ff; font-size: 22px; }
.feature-card h3 { margin: 16px 0 8px; font-size: 18px; }
.feature-card p { color: var(--muted); font-size: 14px; margin: 0; }

.footer { border-top: 1px solid var(--border); background: #fff; padding: 24px 0; }
.footer-wrap { display: flex; align-items: center; justify-content: space-between; gap: 20px; color: #7a869a; font-size: 13px; }
.footer-brand { display: flex; align-items: center; gap: 10px; }
.footer-brand > span { font-size: 24px; }
.footer-brand strong, .footer-brand small { display: block; }
.footer-brand strong { color: var(--text); }

@media (max-width: 980px) {
    .nav { display: none; }
    .hero-grid { grid-template-columns: 1fr; padding: 58px 0; min-height: auto; }
    .hero-card { min-height: 320px; }
    .class-grid, .feature-grid { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 620px) {
    .shell { width: min(100% - 24px, 1180px); }
    .nav-wrap { min-height: 66px; }
    .brand small { display: none; }
    .hero-grid { gap: 34px; padding: 42px 0 48px; }
    .hero h1 { font-size: 47px; }
    .hero p { font-size: 16px; }
    .hero-actions, .btn { width: 100%; }
    .desk-card { height: 300px; }
    .laptop { transform: scale(.82); transform-origin: right bottom; }
    .books { transform: scale(.86); transform-origin: left bottom; }
    .plant { right: 6px; bottom: 135px; }
    .hero-note { font-size: 17px; right: 20px; }
    .section { padding: 52px 0; }
    .section-heading { align-items: flex-start; flex-direction: column; }
    .section-heading h2 { font-size: 28px; }
    .class-grid, .feature-grid { grid-template-columns: 1fr; }
    .footer-wrap { flex-direction: column; align-items: flex-start; }
}