/* Token: xem DESIGN.md (đã đo tương phản). Component không viết mã hex. */
:root {
  --bg: #f5f6fb; --surface: #ffffff; --surface-2: #f8fafc; --border: #e2e8f0; --border-strong: #6b7a90;
  --text: #0f172a; --text-2: #334155; --muted: #5b6b7f;
  --primary: #4338ca; --primary-hover: #3730a3; --on-primary: #ffffff; --primary-soft: #eef2ff; --ring: #4f46e5;
  --ok: #047857; --ok-text: #065f46; --ok-soft: #ecfdf5;
  --bad: #b91c1c; --bad-text: #991b1b; --bad-soft: #fef2f2;
  --warn: #92400e; --warn-soft: #fffbeb;
  --nav-bg: #1e1b4b; --nav-text: #ffffff; --nav-muted: #c7d2fe; --nav-active: #312e81; --brand: #4f46e5; --on-brand: #ffffff; --nav-indicator: #818cf8;
  --shadow: 0 1px 2px rgba(15, 23, 42, .06), 0 1px 3px rgba(15, 23, 42, .08);
  --tap: 44px; --r-sm: 6px; --r-md: 10px; --r-lg: 14px;
  --font: "Be Vietnam Pro", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --font-han: "Noto Sans SC", "Microsoft YaHei", "PingFang SC", "Hiragino Sans GB", sans-serif;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0b1020; --surface: #141a2e; --surface-2: #1a2138; --border: #26304d; --border-strong: #64748b;
    --text: #e2e8f0; --text-2: #cbd5e1; --muted: #94a3b8;
    --primary: #a5b4fc; --primary-hover: #c7d2fe; --on-primary: #0b1020; --primary-soft: #25295a; --ring: #a5b4fc;
    --ok: #34d399; --ok-text: #6ee7b7; --ok-soft: #0f2f27;
    --bad: #f87171; --bad-text: #fca5a5; --bad-soft: #3a1616;
    --warn: #fcd34d; --warn-soft: #33240a;
    --nav-bg: #0f1330; --nav-active: #25295a;
    --shadow: 0 1px 2px rgba(0, 0, 0, .4);
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #0b1020; --surface: #141a2e; --surface-2: #1a2138; --border: #26304d; --border-strong: #64748b;
  --text: #e2e8f0; --text-2: #cbd5e1; --muted: #94a3b8;
  --primary: #a5b4fc; --primary-hover: #c7d2fe; --on-primary: #0b1020; --primary-soft: #25295a; --ring: #a5b4fc;
  --ok: #34d399; --ok-text: #6ee7b7; --ok-soft: #0f2f27;
  --bad: #f87171; --bad-text: #fca5a5; --bad-soft: #3a1616;
  --warn: #fcd34d; --warn-soft: #33240a;
  --nav-bg: #0f1330; --nav-active: #25295a;
  --shadow: 0 1px 2px rgba(0, 0, 0, .4);
  color-scheme: dark;
}

*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--bg); color: var(--text); font: 400 16px/1.55 var(--font); }
h1, h2, h3 { line-height: 1.3; margin: 0 0 8px; color: var(--text); }
h1 { font-size: 28px; font-weight: 600; }
h2 { font-size: 18px; font-weight: 600; }
h3 { font-size: 16px; font-weight: 600; }
p { margin: 0 0 12px; }
a { color: var(--primary); }
button, input, select, textarea { font: inherit; color: inherit; }
.ic { flex: none; display: block; }
.han { font-family: var(--font-han); font-weight: 500; overflow-wrap: anywhere; }
.py { color: var(--primary); font-weight: 500; }
.muted { color: var(--muted); }
.num { font-variant-numeric: tabular-nums; }
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; border: 0; }

:focus-visible { outline: 3px solid var(--ring); outline-offset: 2px; border-radius: 4px; }
h1[tabindex="-1"]:focus, main[tabindex="-1"]:focus { outline: none; } /* tiêu đề nhận focus khi đổi trang, không phải phần tử bấm được */
.skip { position: absolute; left: 8px; top: -60px; z-index: 100; background: var(--primary); color: var(--on-primary); padding: 10px 16px; border-radius: var(--r-sm); font-weight: 600; text-decoration: none; }
.skip:focus { top: 8px; }

/* ---------- Bố cục & điều hướng ---------- */
.topbar { position: sticky; top: 0; z-index: 20; display: flex; align-items: center; justify-content: space-between; gap: 8px; padding: 0 8px 0 16px; min-height: 56px; background: var(--nav-bg); color: var(--nav-text); }
.brand { display: flex; align-items: center; gap: 10px; font-weight: 600; color: var(--nav-text); text-decoration: none; min-height: var(--tap); }
.brand-mark { width: 32px; height: 32px; border-radius: 8px; display: grid; place-items: center; background: var(--brand); color: var(--on-brand); font-family: var(--font-han); font-size: 18px; }
.brand small { display: block; font-weight: 400; font-size: 12px; color: var(--nav-muted); }
.icon-btn { display: inline-flex; align-items: center; justify-content: center; min-width: var(--tap); min-height: var(--tap); border: 0; border-radius: var(--r-md); background: transparent; color: inherit; cursor: pointer; }
.topbar .icon-btn:hover { background: var(--nav-active); }

.sidebar { display: none; }
.main { padding: 16px 16px calc(88px + env(safe-area-inset-bottom)); max-width: 960px; margin: 0 auto; }
.bottomnav { position: fixed; left: 0; right: 0; bottom: 0; z-index: 20; display: grid; grid-template-columns: repeat(5, 1fr); background: var(--surface); border-top: 1px solid var(--border); padding-bottom: env(safe-area-inset-bottom); }
.bottomnav a { display: flex; flex-direction: column; align-items: center; justify-content: center; gap: 2px; min-height: 60px; padding: 6px 2px; font-size: 12px; color: var(--muted); text-decoration: none; text-align: center; }
.bottomnav a[aria-current="page"] { color: var(--primary); font-weight: 600; }
.bottomnav a[aria-current="page"] .ic { stroke-width: 2.4; }

@media (min-width: 1024px) {
  .topbar { display: none; }
  .bottomnav { display: none; }
  .layout { display: grid; grid-template-columns: 248px 1fr; min-height: 100vh; }
  .sidebar { display: flex; flex-direction: column; gap: 4px; position: sticky; top: 0; height: 100vh; padding: 20px 12px; background: var(--nav-bg); color: var(--nav-text); }
  .sidebar .brand { padding: 0 8px 16px; }
  .sidebar nav a { display: flex; align-items: center; gap: 12px; min-height: var(--tap); padding: 0 12px; border-radius: var(--r-md); color: var(--nav-muted); text-decoration: none; font-weight: 500; }
  .sidebar nav a:hover { background: var(--nav-active); color: var(--nav-text); }
  .sidebar nav a[aria-current="page"] { background: var(--nav-active); color: var(--nav-text); box-shadow: inset 3px 0 0 var(--nav-indicator); }
  .sidebar .side-foot { margin-top: auto; padding: 12px; font-size: 13px; color: var(--nav-muted); }
  .main { padding: 32px 40px 48px; }
}

/* ---------- Thành phần ---------- */
.page-head { margin-bottom: 20px; }
.page-head p { color: var(--muted); margin: 0; }
.back { display: inline-flex; align-items: center; gap: 4px; min-height: var(--tap); margin-bottom: 4px; color: var(--primary); text-decoration: none; font-weight: 500; }

.card { background: var(--surface); border: 1px solid var(--border); border-radius: var(--r-lg); padding: 16px; box-shadow: var(--shadow); }
.stack > * + * { margin-top: 12px; }
.grid { display: grid; gap: 12px; }
@media (min-width: 640px) { .grid-2 { grid-template-columns: repeat(2, 1fr); } .grid-3 { grid-template-columns: repeat(3, 1fr); } }
.section { margin-top: 28px; }

.btn { display: inline-flex; align-items: center; justify-content: center; gap: 8px; min-height: var(--tap); padding: 0 16px; border-radius: var(--r-md); border: 1px solid var(--border-strong); background: var(--surface); color: var(--text); font-weight: 500; cursor: pointer; text-decoration: none; transition: background-color .15s, border-color .15s, color .15s; }
.btn:hover { background: var(--surface-2); }
.btn-primary { background: var(--primary); border-color: var(--primary); color: var(--on-primary); }
.btn-primary:hover { background: var(--primary-hover); border-color: var(--primary-hover); }
.btn-ghost { border-color: transparent; background: transparent; color: var(--primary); }
.btn-ghost:hover { background: var(--primary-soft); }
.btn-danger { color: var(--bad); border-color: var(--bad); }
.btn[disabled] { opacity: .55; cursor: not-allowed; }
.btn[aria-busy="true"] .ic { animation: pulse 1s ease-in-out infinite; }
.btn-block { width: 100%; }
.btn-row { display: flex; flex-wrap: wrap; gap: 8px; }
.speak { min-width: var(--tap); padding: 0; color: var(--primary); border-color: var(--border); }

.stat { display: flex; align-items: center; gap: 12px; }
.stat-ic { width: 44px; height: 44px; border-radius: 12px; display: grid; place-items: center; background: var(--primary-soft); color: var(--primary); }
.stat-ic.warn { background: var(--warn-soft); color: var(--warn); }
.stat-ic.ok { background: var(--ok-soft); color: var(--ok-text); }
.stat b { display: block; font-size: 22px; font-variant-numeric: tabular-nums; line-height: 1.2; }
.stat span { font-size: 14px; color: var(--muted); }

.progress { height: 8px; border-radius: 99px; background: var(--border); overflow: hidden; }
.progress > i { display: block; height: 100%; background: var(--ok); border-radius: 99px; }

.topic { display: flex; align-items: center; gap: 12px; min-height: 72px; text-decoration: none; color: var(--text); }
.topic:hover { border-color: var(--primary); }
.topic .stat-ic { flex: none; }
.topic-body { flex: 1; min-width: 0; }
.topic-body strong { display: block; font-weight: 600; }
.topic-body small { display: block; color: var(--muted); font-size: 13px; }
.topic-body .progress { margin-top: 8px; }
.topic-count { font-size: 13px; color: var(--muted); font-variant-numeric: tabular-nums; white-space: nowrap; }

.field { display: flex; flex-direction: column; gap: 6px; }
.field label { font-weight: 500; font-size: 14px; }
.input, .select { min-height: var(--tap); width: 100%; padding: 8px 12px; border: 1px solid var(--border-strong); border-radius: var(--r-md); background: var(--surface); font-size: 16px; }
.search { position: relative; }
.search .ic { position: absolute; left: 12px; top: 50%; transform: translateY(-50%); color: var(--muted); }
.search .input { padding-left: 40px; }

.word { display: flex; align-items: flex-start; gap: 12px; padding: 14px 16px; }
.word + .word { border-top: 1px solid var(--border); }
.word-main { flex: 1; min-width: 0; }
.word-main .han { font-size: 24px; line-height: 1.3; }
.word-main .py { font-size: 15px; margin-left: 8px; }
.word-main .vi { color: var(--text-2); margin: 2px 0 0; }
.word-ex { margin-top: 8px; padding: 8px 12px; border-left: 3px solid var(--primary-soft); background: var(--surface-2); border-radius: 0 var(--r-sm) var(--r-sm) 0; font-size: 14px; }
.word-ex .han { font-size: 16px; font-weight: 400; }
.badge { display: inline-flex; align-items: center; gap: 4px; padding: 2px 8px; border-radius: 99px; font-size: 12px; font-weight: 500; white-space: nowrap; }
.badge.ok { background: var(--ok-soft); color: var(--ok-text); }
.badge.warn { background: var(--warn-soft); color: var(--warn); }
.badge.new { background: var(--primary-soft); color: var(--primary); }
.list { padding: 0; overflow: hidden; }

.chips { display: flex; flex-wrap: wrap; gap: 8px; }
.chip { min-height: var(--tap); padding: 0 14px; border-radius: 99px; border: 1px solid var(--border-strong); background: var(--surface); cursor: pointer; font-size: 14px; }
.chip[aria-pressed="true"] { background: var(--primary); border-color: var(--primary); color: var(--on-primary); font-weight: 600; }

/* Thẻ ghi nhớ */
.flash { text-align: center; padding: 32px 16px; min-height: 280px; display: flex; flex-direction: column; align-items: center; justify-content: center; gap: 8px; }
.flash .han { font-size: clamp(44px, 12vw, 72px); line-height: 1.2; }
.flash .py { font-size: 22px; }
.flash .vi { font-size: 18px; color: var(--text-2); }
.flash .word-ex .han { font-size: 18px; line-height: 1.5; font-weight: 400; }
.flash .word-ex .py { font-size: 14px; }
.flash-meta { display: flex; justify-content: space-between; align-items: center; margin-bottom: 12px; color: var(--muted); font-size: 14px; }
.rate { display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px; margin-top: 16px; }
.rate .btn { flex-direction: column; gap: 0; min-height: 56px; padding: 4px; font-weight: 600; }
.rate .btn small { font-weight: 400; font-size: 12px; color: var(--muted); }
.rate .r0 { color: var(--bad); border-color: var(--bad); }
.rate .r1 { color: var(--warn); border-color: var(--warn); }
.rate .r2 { color: var(--primary); border-color: var(--primary); }
.rate .r3 { color: var(--ok); border-color: var(--ok); }
.kbd-hint { margin-top: 12px; font-size: 13px; color: var(--muted); text-align: center; }

/* Luyện tập */
.quiz-q { text-align: center; padding: 24px 16px; }
.quiz-q .han { font-size: clamp(36px, 10vw, 56px); }
.opts { display: grid; gap: 8px; margin-top: 16px; }
@media (min-width: 640px) { .opts { grid-template-columns: repeat(2, 1fr); } }
.opt { display: flex; align-items: center; gap: 10px; min-height: 56px; padding: 10px 14px; text-align: left; border: 1px solid var(--border-strong); border-radius: var(--r-md); background: var(--surface); cursor: pointer; }
.opt:hover:not([disabled]) { border-color: var(--primary); background: var(--primary-soft); }
.opt .han { font-size: 22px; }
.opt.correct { border-color: var(--ok); background: var(--ok-soft); color: var(--ok-text); }
.opt.wrong { border-color: var(--bad); background: var(--bad-soft); color: var(--bad-text); }
.opt[disabled] { cursor: default; }
.opt-key { flex: none; width: 26px; height: 26px; border-radius: 6px; display: grid; place-items: center; font-size: 13px; border: 1px solid var(--border); color: var(--muted); }

.note { display: flex; gap: 10px; align-items: flex-start; padding: 12px 14px; border-radius: var(--r-md); font-size: 15px; }
.note .ic { margin-top: 2px; }
.note.ok { background: var(--ok-soft); color: var(--ok-text); }
.note.bad { background: var(--bad-soft); color: var(--bad-text); }
.note.warn { background: var(--warn-soft); color: var(--warn); }
.note.info { background: var(--primary-soft); color: var(--primary); }

.empty { text-align: center; padding: 32px 16px; color: var(--muted); }
.empty .ic { margin: 0 auto 8px; color: var(--muted); }
.empty strong { display: block; color: var(--text); margin-bottom: 4px; }

/* Hội thoại */
.line { display: flex; gap: 10px; align-items: flex-start; }
.line + .line { margin-top: 12px; }
.line.me { flex-direction: row-reverse; }
.bubble { max-width: min(560px, 85%); padding: 10px 14px; border-radius: 14px; background: var(--surface); border: 1px solid var(--border); }
.line.me .bubble { background: var(--primary-soft); border-color: transparent; }
.bubble .who { font-size: 12px; color: var(--muted); font-weight: 500; }
.bubble .han { font-size: 19px; line-height: 1.5; font-weight: 400; }
.bubble .py { font-size: 14px; font-weight: 400; }
.bubble .vi { font-size: 14px; color: var(--text-2); margin-top: 2px; }
.bubble .tools { display: flex; gap: 4px; margin-top: 6px; flex-wrap: wrap; }
.bubble.playing { outline: 2px solid var(--ring); }
.score { font-weight: 600; font-variant-numeric: tabular-nums; }
.toolbar { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; margin-bottom: 16px; }

.result-big { font-size: 44px; font-weight: 600; font-variant-numeric: tabular-nums; line-height: 1.1; }
.toggle { display: flex; align-items: center; justify-content: space-between; gap: 12px; min-height: var(--tap); }
.toggle input { width: 22px; height: 22px; accent-color: var(--primary); }
.row-between { display: flex; justify-content: space-between; align-items: center; gap: 12px; flex-wrap: wrap; }

@keyframes pulse { 50% { opacity: .35; } }
.fade-in { animation: fade .18s ease-out; }
@keyframes fade { from { opacity: 0; transform: translateY(4px); } to { opacity: 1; transform: none; } }
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation: none !important; transition: none !important; }
}