/* Tiếng Anh Công Sở — giao diện web
   Màu thương hiệu lấy từ app (flutter_app/lib/theme.dart): tím #6D28D9 → cyan #06B6D4, nhấn cam #FB923C.
   Bố cục/nhịp điệu học theo các site edu của NextAI (nextai-web-new, portal NextEdu). */

:root {
  --bg: #ffffff;
  --bg-soft: #f8fafc;
  --bg-muted: #f1f5f9;
  --bg-dark: #0b1120;
  --text: #0f172a;
  --text-muted: #5b6b82;
  --border: #e2e8f0;
  --border-strong: #cbd5e1;

  --primary: #6d28d9;
  --primary-hover: #5b21b6;
  --primary-soft: #f3edff;
  --cyan: #06b6d4;
  --cyan-soft: #e6f9fd;
  --accent: #fb923c;
  --accent-ink: #9a3f06;
  --accent-soft: #fff3e8;
  --good: #059669;
  --good-soft: #e8f8f1;
  --warn: #b45309;
  --warn-soft: #fff7e6;
  --bad: #dc2626;
  --bad-soft: #fdecec;

  --grad: linear-gradient(135deg, #6d28d9 0%, #06b6d4 100%);
  --grad-soft: radial-gradient(60% 70% at 15% 0%, rgba(109, 40, 217, .14) 0%, transparent 70%),
               radial-gradient(50% 60% at 90% 10%, rgba(6, 182, 212, .16) 0%, transparent 70%);

  --shadow-sm: 0 1px 2px rgba(15, 23, 42, .06);
  --shadow-md: 0 8px 24px rgba(15, 23, 42, .08);
  --shadow-lg: 0 24px 56px rgba(15, 23, 42, .14);
  --r-sm: 10px; --r: 14px; --r-lg: 22px;
  --container: 1120px;
  --header-h: 64px;
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", Inter, Roboto, "Helvetica Neue", Arial, sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0b1120; --bg-soft: #0f172a; --bg-muted: #162033;
    --text: #e8edf6; --text-muted: #9aa8bf;
    --border: #1e293b; --border-strong: #2c3a52;
    --primary: #a78bfa; --primary-hover: #c4b5fd; --primary-soft: #1d1536;
    --cyan-soft: #0b2a33; --accent-soft: #2b1a0c; --accent-ink: #fdba74;
    --good: #34d399; --good-soft: #0c2a20; --warn: #fbbf24; --warn-soft: #2b2208;
    --bad: #f87171; --bad-soft: #301414;
    --shadow-md: 0 8px 24px rgba(0,0,0,.4); --shadow-lg: 0 24px 56px rgba(0,0,0,.5);
  }
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; scroll-padding-top: calc(var(--header-h) + 16px); -webkit-text-size-adjust: 100%; }
body { font-family: var(--font); font-size: 16px; line-height: 1.65; color: var(--text); background: var(--bg); -webkit-font-smoothing: antialiased; }
img, svg { max-width: 100%; display: block; }
a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }
h1, h2, h3, h4 { line-height: 1.25; letter-spacing: -.015em; }
h1 { font-size: clamp(1.9rem, 4.2vw, 3rem); font-weight: 800; }
h2 { font-size: clamp(1.45rem, 2.6vw, 2rem); font-weight: 750; }
h3 { font-size: 1.15rem; font-weight: 700; }
p + p { margin-top: .8em; }
:focus-visible { outline: 3px solid var(--cyan); outline-offset: 2px; border-radius: 6px; }
.container { width: min(100% - 32px, var(--container)); margin-inline: auto; }
.skip { position: absolute; left: -999px; top: 8px; background: var(--primary); color: #fff; padding: 8px 14px; border-radius: 8px; z-index: 100; }
.skip:focus { left: 8px; }
.muted { color: var(--text-muted); }
.sr { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); }

/* ── Header ─────────────────────────────────────────── */
.site-header { position: sticky; top: 0; z-index: 50; height: var(--header-h); background: color-mix(in srgb, var(--bg) 88%, transparent); backdrop-filter: saturate(160%) blur(12px); border-bottom: 1px solid var(--border); }
.site-header .container { height: 100%; display: flex; align-items: center; justify-content: space-between; gap: 16px; }
.brand { display: flex; align-items: center; gap: 10px; font-weight: 800; color: var(--text); letter-spacing: -.02em; }
.brand:hover { text-decoration: none; }
.brand img { width: 34px; height: 34px; border-radius: 9px; }
.nav { display: flex; align-items: center; gap: 4px; margin-left: auto; }
.nav a { color: var(--text-muted); font-weight: 600; font-size: .94rem; padding: 8px 12px; border-radius: 10px; }
.nav a:hover, .nav a[aria-current="page"] { color: var(--primary); background: var(--primary-soft); text-decoration: none; }
.head-actions { display: flex; align-items: center; gap: 8px; }
.menu-btn { display: none; }
.account-chip { display: inline-flex; align-items: center; gap: 8px; font-weight: 700; font-size: .88rem; padding: 7px 12px; border-radius: 10px; border: 1px solid var(--border-strong); color: var(--text); max-width: 190px; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.account-chip:hover { background: var(--bg-muted); text-decoration: none; }
@media (max-width: 960px) {
  .nav { position: absolute; top: var(--header-h); left: 0; right: 0; flex-direction: column; align-items: stretch; background: var(--bg); border-bottom: 1px solid var(--border); padding: 10px 16px 16px; display: none; }
  .nav.open { display: flex; }
  .menu-btn { display: inline-flex; align-items: center; justify-content: center; width: 42px; height: 42px; border-radius: 10px; border: 1px solid var(--border); background: var(--bg); color: var(--text); cursor: pointer; font-size: 1.2rem; }
}

/* ── Buttons / chips ────────────────────────────────── */
.btn { display: inline-flex; align-items: center; justify-content: center; gap: 8px; font: inherit; font-weight: 700; font-size: .98rem; padding: 12px 20px; border-radius: 12px; border: 1px solid transparent; cursor: pointer; transition: transform .15s, box-shadow .15s, background .15s; text-decoration: none !important; }
.btn:active { transform: translateY(1px); }
.btn-primary { background: var(--grad); color: #fff; box-shadow: 0 8px 22px rgba(109, 40, 217, .28); }
.btn-primary:hover { box-shadow: 0 12px 30px rgba(109, 40, 217, .38); }
.btn-accent { background: var(--accent); color: #2a1300; }
.btn-accent:hover { background: #f97316; }
.btn-ghost { background: var(--bg); color: var(--text); border-color: var(--border-strong); }
.btn-ghost:hover { background: var(--bg-muted); }
.btn-sm { padding: 8px 14px; font-size: .88rem; border-radius: 10px; }
.btn[disabled] { opacity: .5; cursor: not-allowed; }
.chip { display: inline-flex; align-items: center; gap: 6px; font-size: .78rem; font-weight: 700; padding: 3px 10px; border-radius: 999px; background: var(--bg-muted); color: var(--text-muted); border: 1px solid var(--border); }
.chip.lv-A2 { background: var(--good-soft); color: var(--good); border-color: transparent; }
.chip.lv-B1 { background: var(--cyan-soft); color: #0e7490; border-color: transparent; }
.chip.lv-B2 { background: var(--primary-soft); color: var(--primary); border-color: transparent; }
.chip.lv-C1 { background: var(--accent-soft); color: var(--accent-ink); border-color: transparent; }
.chip.done { background: var(--good-soft); color: var(--good); border-color: transparent; }
@media (prefers-color-scheme: dark) { .chip.lv-B1 { color: #67e8f9; } }

/* ── Hero ───────────────────────────────────────────── */
.hero { position: relative; background: var(--grad-soft); padding: clamp(40px, 7vw, 88px) 0 clamp(36px, 6vw, 72px); overflow: hidden; }
.hero .grid { display: grid; grid-template-columns: 1.15fr .85fr; gap: 40px; align-items: center; }
.eyebrow { display: inline-flex; gap: 8px; align-items: center; font-weight: 700; font-size: .85rem; color: var(--primary); background: var(--primary-soft); padding: 6px 12px; border-radius: 999px; margin-bottom: 18px; }
.grad-text { background: var(--grad); -webkit-background-clip: text; background-clip: text; color: transparent; }
.lead { font-size: clamp(1.02rem, 1.6vw, 1.2rem); color: var(--text-muted); margin-top: 16px; max-width: 58ch; }
.cta-row { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 28px; }
.stats { display: flex; flex-wrap: wrap; gap: 10px 22px; margin-top: 30px; }
.stat b { display: block; font-size: 1.5rem; font-weight: 800; letter-spacing: -.02em; }
.stat span { font-size: .85rem; color: var(--text-muted); }
@media (max-width: 860px) { .hero .grid { grid-template-columns: 1fr; } }

.page-hero { background: var(--grad-soft); padding: 34px 0 30px; border-bottom: 1px solid var(--border); }
.page-hero h1 { font-size: clamp(1.7rem, 3.4vw, 2.5rem); }
.page-hero .lead { margin-top: 12px; }
.crumbs { display: flex; flex-wrap: wrap; gap: 6px; font-size: .86rem; color: var(--text-muted); margin-bottom: 14px; list-style: none; }
.crumbs li + li::before { content: "›"; margin-right: 6px; opacity: .6; }
.crumbs a { color: var(--text-muted); }

/* ── Sections / cards ───────────────────────────────── */
section.block { padding: clamp(36px, 5.5vw, 68px) 0; }
section.block.soft { background: var(--bg-soft); border-block: 1px solid var(--border); }
.section-head { max-width: 62ch; margin-bottom: 28px; }
.section-head p { color: var(--text-muted); margin-top: 8px; }
/* 3 cột đều nhau: 3 thẻ và 6 thẻ luôn dàn kín hàng. Số thẻ ít thì co cột cho khỏi trống bên phải. */
.grid-cards { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 16px; }
.grid-cards:has(> :nth-child(2):last-child), .grid-cards:has(> :nth-child(4):last-child) { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid-cards:has(> :only-child) { grid-template-columns: minmax(0, 1fr); }
@media (max-width: 900px) { .grid-cards, .grid-cards:has(> :nth-child(2):last-child), .grid-cards:has(> :nth-child(4):last-child) { grid-template-columns: repeat(2, minmax(0, 1fr)); } }
@media (max-width: 600px) { .grid-cards, .grid-cards:has(> :nth-child(n)) { grid-template-columns: minmax(0, 1fr); } }
.card { display: flex; flex-direction: column; gap: 10px; background: var(--bg); border: 1px solid var(--border); border-radius: var(--r); padding: 20px; box-shadow: var(--shadow-sm); transition: transform .18s, box-shadow .18s, border-color .18s; color: inherit; }
a.card:hover { transform: translateY(-3px); box-shadow: var(--shadow-md); border-color: var(--border-strong); text-decoration: none; }
.card h3 { color: var(--text); }
.card p { color: var(--text-muted); font-size: .94rem; }
.card .meta { display: flex; flex-wrap: wrap; gap: 6px; margin-top: auto; padding-top: 6px; }
.card .arrow { margin-top: auto; font-weight: 700; color: var(--primary); font-size: .92rem; }
.card.track { border-top: 4px solid var(--primary); }
.card.track.t2 { border-top-color: var(--cyan); }
.card.track.t3 { border-top-color: var(--accent); }
.icon-bubble { width: 44px; height: 44px; border-radius: 12px; display: grid; place-items: center; font-size: 1.4rem; background: var(--primary-soft); }
.tags { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 4px; }
.tag { font-size: .84rem; font-weight: 600; padding: 5px 11px; border-radius: 999px; background: var(--bg-muted); color: var(--text); border: 1px solid var(--border); }
a.tag:hover { background: var(--primary-soft); color: var(--primary); text-decoration: none; }

.steps { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 16px; counter-reset: s; }
.step { position: relative; padding: 18px 18px 18px 18px; border: 1px solid var(--border); border-radius: var(--r); background: var(--bg); }
.step::before { counter-increment: s; content: counter(s); display: grid; place-items: center; width: 30px; height: 30px; border-radius: 50%; background: var(--grad); color: #fff; font-weight: 800; font-size: .9rem; margin-bottom: 10px; }
.step p { color: var(--text-muted); font-size: .92rem; margin-top: 4px; }

.banner { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 20px; background: var(--bg-dark); color: #e2e8f0; border-radius: var(--r-lg); padding: clamp(24px, 4vw, 40px); position: relative; overflow: hidden; }
.banner::after { content: ""; position: absolute; inset: auto -60px -80px auto; width: 280px; height: 280px; border-radius: 50%; background: var(--grad); opacity: .35; filter: blur(50px); }
.banner > * { position: relative; z-index: 1; }
.banner h2 { color: #fff; }
.banner p { color: #b6c2d6; margin-top: 8px; max-width: 56ch; }

/* ── Scenario page ──────────────────────────────────── */
.layout { display: grid; grid-template-columns: minmax(0, 1fr) 300px; gap: 32px; padding: 32px 0 56px; align-items: start; }
@media (max-width: 960px) { .layout { grid-template-columns: 1fr; } }
.stack > * + * { margin-top: 24px; }
.panel { background: var(--bg); border: 1px solid var(--border); border-radius: var(--r); padding: 22px; }
.panel > h2 { font-size: 1.25rem; margin-bottom: 12px; }
.aside { position: sticky; top: calc(var(--header-h) + 16px); display: flex; flex-direction: column; gap: 16px; }
@media (max-width: 960px) { .aside { position: static; } }
.context { font-size: 1.06rem; padding: 18px 20px; border-left: 4px solid var(--cyan); background: var(--cyan-soft); border-radius: 0 var(--r) var(--r) 0; }
.phrases { list-style: none; display: grid; gap: 10px; }
.phrase { display: flex; align-items: center; justify-content: space-between; gap: 10px; padding: 12px 14px; border: 1px solid var(--border); border-radius: 12px; background: var(--bg-soft); }
.phrase q { quotes: none; font-weight: 650; font-size: 1.04rem; }
.icon-btn { flex: none; width: 36px; height: 36px; display: inline-grid; place-items: center; border-radius: 10px; border: 1px solid var(--border); background: var(--bg); cursor: pointer; font-size: 1rem; color: var(--text); }
.icon-btn:hover { background: var(--primary-soft); }
.callout { padding: 14px 16px; border-radius: 12px; border: 1px solid var(--border); background: var(--bg-soft); }
.callout + .callout { margin-top: 12px; }
.callout h3 { font-size: 1rem; margin-bottom: 4px; }
.callout .ex { margin-top: 6px; font-style: italic; color: var(--text-muted); font-size: .95rem; }
.vocab { display: grid; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr)); gap: 12px; }
.vocab .callout { margin: 0; }
.vocab b { color: var(--primary); }
.rubric { list-style: none; display: grid; gap: 8px; margin-top: 12px; }
.rubric label { display: flex; gap: 10px; align-items: flex-start; padding: 10px 12px; border: 1px solid var(--border); border-radius: 10px; cursor: pointer; background: var(--bg); }
.rubric input { margin-top: 5px; accent-color: var(--primary); width: 17px; height: 17px; }
.rubric label:has(input:checked) { background: var(--good-soft); border-color: transparent; }
textarea.write { width: 100%; min-height: 150px; resize: vertical; font: inherit; padding: 14px; border-radius: 12px; border: 1px solid var(--border-strong); background: var(--bg); color: var(--text); line-height: 1.6; }
textarea.write:focus { border-color: var(--primary); outline: 3px solid color-mix(in srgb, var(--primary) 25%, transparent); }
.row { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; }
.row.between { justify-content: space-between; }
.progressbar { height: 8px; border-radius: 99px; background: var(--bg-muted); overflow: hidden; }
.progressbar > i { display: block; height: 100%; width: 0; background: var(--grad); transition: width .3s; }
.nextprev { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
.nextprev a { display: block; padding: 14px 16px; border: 1px solid var(--border); border-radius: 12px; color: var(--text); }
.nextprev a small { display: block; color: var(--text-muted); font-size: .78rem; margin-bottom: 2px; }
.nextprev a:hover { background: var(--bg-soft); text-decoration: none; }
.nextprev a:last-child { text-align: right; }
.side-list { list-style: none; display: grid; gap: 4px; }
.side-list a { display: block; padding: 8px 10px; border-radius: 8px; color: var(--text); font-size: .93rem; }
.side-list a:hover { background: var(--bg-muted); text-decoration: none; }

/* ── Filters / list ─────────────────────────────────── */
.filters { display: flex; flex-wrap: wrap; gap: 10px; margin-bottom: 20px; }
.filters input[type=search], .filters select { font: inherit; padding: 10px 14px; border-radius: 10px; border: 1px solid var(--border-strong); background: var(--bg); color: var(--text); }
.filters input[type=search] { flex: 1 1 240px; }
[hidden] { display: none !important; }
.empty { padding: 28px; text-align: center; color: var(--text-muted); border: 1px dashed var(--border-strong); border-radius: var(--r); }

/* ── Interactive players ────────────────────────────── */
.player { background: var(--bg); border: 1px solid var(--border); border-radius: var(--r-lg); box-shadow: var(--shadow-md); padding: clamp(18px, 3vw, 30px); }
.player .q { font-size: clamp(1.4rem, 3vw, 2rem); font-weight: 800; text-align: center; padding: 22px 8px; letter-spacing: 0; }
.player .q.small { font-size: 1.12rem; font-weight: 650; text-align: left; line-height: 1.6; }
.answer-row { display: flex; gap: 10px; flex-wrap: wrap; }
.answer-row input { flex: 1 1 220px; font: inherit; font-size: 1.1rem; padding: 12px 14px; border-radius: 12px; border: 2px solid var(--border-strong); background: var(--bg); color: var(--text); }
.answer-row input:focus { border-color: var(--primary); outline: none; }
.answer-row input.ok { border-color: var(--good); background: var(--good-soft); }
.answer-row input.no { border-color: var(--bad); animation: shake .3s; }
@keyframes shake { 25% { transform: translateX(-5px); } 75% { transform: translateX(5px); } }
.feedback { margin-top: 14px; padding: 12px 14px; border-radius: 12px; font-size: .96rem; }
.feedback.ok { background: var(--good-soft); color: var(--good); }
.feedback.no { background: var(--bad-soft); color: var(--bad); }
.feedback.info { background: var(--warn-soft); color: var(--warn); }
.feedback strong { color: inherit; }
.player-top { display: flex; justify-content: space-between; gap: 12px; align-items: center; margin-bottom: 12px; font-size: .9rem; color: var(--text-muted); }
.score { font-weight: 800; color: var(--primary); }
.result { text-align: center; padding: 18px 0; }
.result .big { font-size: 3rem; font-weight: 800; }
.timer { font-variant-numeric: tabular-nums; font-weight: 800; font-size: 1.3rem; color: var(--primary); }
.timer.low { color: var(--bad); }

.chat { display: flex; flex-direction: column; gap: 12px; max-height: 60vh; overflow-y: auto; padding: 4px 2px 8px; scroll-behavior: smooth; }
.bubble { max-width: 86%; padding: 12px 16px; border-radius: 16px; line-height: 1.55; }
.bubble small { display: block; font-size: .72rem; font-weight: 700; text-transform: uppercase; letter-spacing: .06em; margin-bottom: 3px; opacity: .7; }
.bubble.them { align-self: flex-start; background: var(--bg-muted); border-bottom-left-radius: 4px; }
.bubble.me { align-self: flex-end; background: var(--primary); color: #fff; border-bottom-right-radius: 4px; }
@media (prefers-color-scheme: dark) { .bubble.me { color: #14082b; } }
.bubble.sys { align-self: center; max-width: 100%; background: var(--warn-soft); color: var(--warn); border-radius: 12px; text-align: center; font-weight: 600; }
.note { align-self: flex-end; max-width: 86%; font-size: .88rem; padding: 8px 12px; border-radius: 10px; }
.note.good { background: var(--good-soft); color: var(--good); }
.note.ok { background: var(--warn-soft); color: var(--warn); }
.note.bad { background: var(--bad-soft); color: var(--bad); }
.choices { display: grid; gap: 10px; margin-top: 16px; }
.choice { text-align: left; font: inherit; padding: 13px 16px; border-radius: 12px; border: 1px solid var(--border-strong); background: var(--bg); color: var(--text); cursor: pointer; line-height: 1.5; transition: background .15s, border-color .15s; }
.choice:hover:not([disabled]) { background: var(--primary-soft); border-color: var(--primary); }
.choice[disabled] { opacity: .55; cursor: default; }

/* ── IELTS / misc ───────────────────────────────────── */
.tabs { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 18px; }
.tabs button { font: inherit; font-weight: 700; padding: 8px 16px; border-radius: 999px; border: 1px solid var(--border-strong); background: var(--bg); color: var(--text); cursor: pointer; }
.tabs button[aria-selected="true"] { background: var(--grad); color: #fff; border-color: transparent; }
.chart { width: 100%; }
.chart text { fill: currentColor; font-size: 11px; }
table.data { width: 100%; border-collapse: collapse; font-size: .95rem; }
table.data th, table.data td { text-align: left; padding: 8px 10px; border-bottom: 1px solid var(--border); }
ol.plain, ul.plain { padding-left: 1.2em; display: grid; gap: 6px; }
details.faq { border: 1px solid var(--border); border-radius: 12px; padding: 14px 18px; background: var(--bg); }
details.faq + details.faq { margin-top: 10px; }
details.faq summary { cursor: pointer; font-weight: 700; }
details.faq p { margin-top: 10px; color: var(--text-muted); }
.pill-nav { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 8px; }

/* ── Footer ─────────────────────────────────────────── */
.site-footer { background: var(--bg-dark); color: #b6c2d6; padding: 44px 0 28px; margin-top: 24px; }
.site-footer a { color: #d6def0; }
.site-footer .cols { display: grid; grid-template-columns: 1.4fr repeat(3, 1fr); gap: 28px; }
.site-footer h4 { color: #fff; font-size: .95rem; margin-bottom: 10px; }
.site-footer ul { list-style: none; display: grid; gap: 6px; font-size: .92rem; }
.site-footer .legal { margin-top: 30px; padding-top: 18px; border-top: 1px solid #1e293b; font-size: .85rem; display: flex; flex-wrap: wrap; gap: 8px 20px; justify-content: space-between; }
@media (max-width: 860px) { .site-footer .cols { grid-template-columns: 1fr 1fr; } }
@media (prefers-reduced-motion: reduce) { * { animation: none !important; transition: none !important; scroll-behavior: auto !important; } }
@media print { .site-header, .site-footer, .aside, .btn, .menu-btn { display: none !important; } .layout { grid-template-columns: 1fr; } }