/* ==========================================================================
   DS103-DTU · Bộ giao diện dùng chung
   Nguyên tắc: nền sáng dễ đọc lâu · 1 màu chính · chữ ≥ 16px · nút ≥ 44px
   ========================================================================== */

:root {
  --bg: #F5F6F8;
  --surface: #FFFFFF;
  --surface-2: #F1F4F7;
  --text: #1F2937;
  --text-strong: #111827;
  --muted: #5B6472;
  --line: #E2E6EC;
  --line-strong: #CBD2DB;

  --primary: #0F766E;
  --primary-hover: #0B5F59;
  --primary-soft: #E3F2EF;
  --primary-ink: #0B4F4A;

  --accent: #B45309;
  --accent-soft: #FEF3C7;
  --success: #15803D;
  --success-soft: #DCFCE7;
  --danger: #B91C1C;
  --danger-soft: #FEE2E2;
  --info: #1D4ED8;
  --info-soft: #DBEAFE;

  --font: 'Be Vietnam Pro', system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
  --mono: 'JetBrains Mono', ui-monospace, Consolas, monospace;
  --fs: 17px;
  --radius: 14px;
  --radius-sm: 10px;
  --shadow: 0 1px 2px rgba(16, 24, 40, .05), 0 1px 3px rgba(16, 24, 40, .06);
  --shadow-lg: 0 10px 30px -8px rgba(16, 24, 40, .18);
  --maxw: 720px;
  --tap: 44px;
}

[data-theme="dark"] {
  --bg: #15181D;
  --surface: #1D2127;
  --surface-2: #252A31;
  --text: #E4E7EB;
  --text-strong: #F3F4F6;
  --muted: #A3ABB6;
  --line: #2E343C;
  --line-strong: #3B424C;
  --primary: #2DD4BF;
  --primary-hover: #5EEAD4;
  --primary-soft: rgba(45, 212, 191, .12);
  --primary-ink: #99F6E4;
  --accent: #FBBF24;
  --accent-soft: rgba(251, 191, 36, .12);
  --success: #4ADE80;
  --success-soft: rgba(74, 222, 128, .12);
  --danger: #F87171;
  --danger-soft: rgba(248, 113, 113, .12);
  --info: #93C5FD;
  --info-soft: rgba(147, 197, 253, .12);
  --shadow: 0 1px 2px rgba(0, 0, 0, .3);
  --shadow-lg: 0 10px 30px -8px rgba(0, 0, 0, .5);
}

[data-fs="lg"] { --fs: 19px; }

*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
body {
  margin: 0; font-family: var(--font); font-size: var(--fs); line-height: 1.65;
  color: var(--text); background: var(--bg); -webkit-font-smoothing: antialiased;
  padding-bottom: env(safe-area-inset-bottom);
}
h1, h2, h3, h4 { color: var(--text-strong); line-height: 1.3; margin: 0 0 .5em; letter-spacing: -.01em; }
h1 { font-size: 1.6rem; } h2 { font-size: 1.3rem; } h3 { font-size: 1.1rem; }
p { margin: 0 0 .9em; }
a { color: var(--primary); }
code, kbd { font-family: var(--mono); font-size: .88em; background: var(--surface-2); border: 1px solid var(--line); border-radius: 6px; padding: .05em .35em; }
button { font: inherit; }
:focus-visible { outline: 3px solid color-mix(in srgb, var(--primary) 45%, transparent); outline-offset: 2px; }
.sr-only { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }
.hidden { display: none !important; }
.muted { color: var(--muted); }
.small { font-size: .875rem; }
.wrap { max-width: var(--maxw); margin: 0 auto; padding: 0 16px; }

/* ---------- Thanh trên ---------- */
.topbar {
  position: sticky; top: 0; z-index: 40; background: color-mix(in srgb, var(--surface) 92%, transparent);
  backdrop-filter: saturate(1.4) blur(10px); -webkit-backdrop-filter: saturate(1.4) blur(10px);
  border-bottom: 1px solid var(--line);
}
.topbar-in { max-width: var(--maxw); margin: 0 auto; padding: 8px 12px; display: flex; align-items: center; gap: 8px; min-height: 56px; }
.topbar .title { flex: 1; min-width: 0; font-weight: 600; font-size: .95rem; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.topbar .title small { display: block; font-weight: 500; color: var(--muted); font-size: .78rem; }
.icon-btn {
  width: var(--tap); height: var(--tap); border-radius: 12px; border: 1px solid transparent; background: transparent;
  color: var(--text); display: inline-grid; place-items: center; cursor: pointer; text-decoration: none; flex: none;
}
.icon-btn:hover { background: var(--surface-2); }
.icon-btn svg { width: 22px; height: 22px; }
.chip-user {
  display: inline-flex; align-items: center; gap: 8px; height: 40px; padding: 0 12px 0 4px; border-radius: 999px;
  background: var(--surface-2); border: 1px solid var(--line); cursor: pointer; color: var(--text); font-size: .85rem; font-weight: 600; max-width: 46vw;
}
.chip-user .av { width: 32px; height: 32px; border-radius: 50%; background: var(--primary); color: #fff; display: grid; place-items: center; font-size: .8rem; flex: none; }
.chip-user span:last-child { white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.progress-line { height: 3px; background: var(--line); }
.progress-line > i { display: block; height: 100%; width: 0; background: var(--primary); transition: width .4s ease; }

/* ---------- Khối nội dung ---------- */
.page { padding-top: 20px; padding-bottom: 120px; }
.hero { padding: 8px 0 16px; }
.eyebrow { display: inline-flex; gap: 6px; align-items: center; font-size: .78rem; font-weight: 600; letter-spacing: .02em; color: var(--primary-ink); background: var(--primary-soft); border-radius: 999px; padding: 4px 10px; margin-bottom: 10px; }
.hero h1 { margin-bottom: 6px; }
.hero p { color: var(--muted); }

.card { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); box-shadow: var(--shadow); }
.card-pad { padding: 18px; }
.stack > * + * { margin-top: 12px; }
.section { margin-top: 28px; }
.section-h { display: flex; align-items: center; gap: 10px; margin-bottom: 12px; }
.section-h .num { width: 30px; height: 30px; border-radius: 50%; background: var(--primary); color: #fff; display: grid; place-items: center; font-weight: 700; font-size: .9rem; flex: none; }
.section-h h2 { margin: 0; font-size: 1.15rem; }

/* Danh sách khối */
.block-list { display: grid; gap: 10px; }
.block-item {
  display: flex; align-items: center; gap: 14px; padding: 14px 16px; text-decoration: none; color: inherit;
  background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); box-shadow: var(--shadow);
  transition: border-color .2s, transform .2s; min-height: 72px;
}
a.block-item:hover { border-color: var(--primary); transform: translateY(-1px); }
.block-item .idx { width: 40px; height: 40px; border-radius: 12px; background: var(--primary-soft); color: var(--primary-ink); display: grid; place-items: center; font-weight: 700; flex: none; }
.block-item .meta { flex: 1; min-width: 0; }
.block-item .meta b { display: block; font-weight: 600; color: var(--text-strong); }
.block-item .meta small { color: var(--muted); font-size: .82rem; }
.block-item.locked { opacity: .65; box-shadow: none; background: var(--surface-2); }
.block-item.locked .idx { background: var(--line); color: var(--muted); }
.badge { display: inline-flex; align-items: center; gap: 4px; font-size: .75rem; font-weight: 600; padding: 3px 9px; border-radius: 999px; background: var(--surface-2); color: var(--muted); border: 1px solid var(--line); white-space: nowrap; }
.badge.ok { background: var(--success-soft); color: var(--success); border-color: transparent; }
.badge.warn { background: var(--accent-soft); color: var(--accent); border-color: transparent; }
.badge.primary { background: var(--primary-soft); color: var(--primary-ink); border-color: transparent; }
.waiting { text-align: center; padding: 22px 16px; border: 1.5px dashed var(--line-strong); border-radius: var(--radius); color: var(--muted); font-size: .92rem; }

/* Tóm tắt */
.points { display: grid; gap: 10px; counter-reset: pt; }
.point { display: flex; gap: 12px; padding: 14px 16px; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); }
.point::before { counter-increment: pt; content: counter(pt); width: 28px; height: 28px; border-radius: 8px; background: var(--accent-soft); color: var(--accent); font-weight: 700; display: grid; place-items: center; flex: none; font-size: .9rem; margin-top: 1px; }
.point b { color: var(--text-strong); }
.point p { margin: 2px 0 0; }
.callout { padding: 14px 16px; border-radius: var(--radius); border-left: 4px solid var(--primary); background: var(--primary-soft); }
.callout.remember { border-left-color: var(--accent); background: var(--accent-soft); }
.callout.warn { border-left-color: var(--danger); background: var(--danger-soft); }
.callout b:first-child { display: block; margin-bottom: 2px; }
.table-wrap { overflow-x: auto; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); }
table.t { width: 100%; border-collapse: collapse; font-size: .92rem; }
table.t th, table.t td { padding: 10px 12px; text-align: left; vertical-align: top; border-bottom: 1px solid var(--line); }
table.t th { background: var(--surface-2); font-weight: 600; color: var(--text-strong); }
table.t tr:last-child td { border-bottom: 0; }

/* Mô phỏng */
.sim { overflow: hidden; }
.sim-head { padding: 12px 16px; border-bottom: 1px solid var(--line); display: flex; align-items: center; gap: 10px; background: var(--surface-2); }
.sim-head b { flex: 1; font-size: .95rem; }
.sim-stage { padding: 18px 16px; min-height: 180px; }
.sim-caption { padding: 12px 16px; border-top: 1px solid var(--line); font-size: .95rem; min-height: 64px; }
.sim-caption .step-label { display: block; font-size: .78rem; font-weight: 700; color: var(--primary-ink); letter-spacing: .02em; margin-bottom: 2px; }
.sim-controls { display: flex; gap: 8px; padding: 12px 16px; border-top: 1px solid var(--line); flex-wrap: wrap; align-items: center; }
.sim-controls .grow { flex: 1; }
.steps-dots { display: flex; gap: 6px; }
.steps-dots i { width: 8px; height: 8px; border-radius: 50%; background: var(--line-strong); transition: background .2s, transform .2s; }
.steps-dots i.on { background: var(--primary); transform: scale(1.25); }

/* Prompt mẫu */
.prompt { border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); overflow: hidden; }
.prompt-h { display: flex; align-items: center; gap: 8px; padding: 10px 12px 10px 16px; border-bottom: 1px solid var(--line); }
.prompt-h b { flex: 1; font-size: .92rem; }
.prompt pre { margin: 0; padding: 14px 16px; font-family: var(--mono); font-size: .86rem; line-height: 1.6; white-space: pre-wrap; word-break: break-word; background: var(--surface-2); }
.prompt.bad .prompt-h { background: var(--danger-soft); }
.prompt.good .prompt-h { background: var(--success-soft); }
.prompt-notes { padding: 10px 16px 14px; display: grid; gap: 6px; font-size: .9rem; }
.prompt-notes span { display: inline-block; font-size: .75rem; font-weight: 700; padding: 1px 8px; border-radius: 6px; background: var(--primary-soft); color: var(--primary-ink); margin-right: 6px; }

/* ---------- Nút ---------- */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px; min-height: var(--tap); padding: 0 18px;
  border-radius: 12px; border: 1px solid var(--line-strong); background: var(--surface); color: var(--text);
  font-weight: 600; font-size: .95rem; cursor: pointer; text-decoration: none; transition: background .15s, border-color .15s, transform .1s;
  -webkit-tap-highlight-color: transparent; user-select: none; white-space: nowrap;
}
.btn:hover { background: var(--surface-2); }
.btn:active { transform: scale(.98); }
.btn:disabled { opacity: .5; cursor: not-allowed; transform: none; }
.btn.primary { background: var(--primary); border-color: var(--primary); color: #fff; }
[data-theme="dark"] .btn.primary { color: #062B28; }
.btn.primary:hover { background: var(--primary-hover); }
.btn.ghost { border-color: transparent; background: transparent; }
.btn.sm { min-height: 36px; padding: 0 12px; font-size: .85rem; border-radius: 10px; }
.btn.block { width: 100%; }
.btn svg { width: 18px; height: 18px; }

/* Thanh điều hướng dưới */
.bottom-nav {
  position: fixed; left: 0; right: 0; bottom: 0; z-index: 30; background: color-mix(in srgb, var(--surface) 94%, transparent);
  backdrop-filter: blur(10px); -webkit-backdrop-filter: blur(10px); border-top: 1px solid var(--line);
  padding: 8px 12px calc(8px + env(safe-area-inset-bottom));
}
.bottom-nav-in { max-width: var(--maxw); margin: 0 auto; display: flex; gap: 8px; }
.bottom-nav .btn { flex: 1; padding: 0 10px; min-width: 0; }

/* ---------- Quiz ---------- */
.quiz-card { padding: 18px; }
.quiz-facts { display: grid; grid-template-columns: repeat(2, 1fr); gap: 8px; margin: 12px 0 16px; }
.fact { background: var(--surface-2); border-radius: var(--radius-sm); padding: 10px 12px; }
.fact small { display: block; color: var(--muted); font-size: .76rem; font-weight: 600; }
.fact b { font-size: 1.05rem; color: var(--text-strong); }

.overlay { position: fixed; inset: 0; z-index: 100; background: var(--bg); display: flex; flex-direction: column; overflow: hidden; }
.overlay-head { background: var(--surface); border-bottom: 1px solid var(--line); }
.overlay-head .row { max-width: var(--maxw); margin: 0 auto; padding: 10px 14px; display: flex; align-items: center; gap: 10px; }
.overlay-head .row b { flex: 1; font-size: .95rem; }
.timer { font-family: var(--mono); font-weight: 700; font-size: 1.05rem; padding: 4px 12px; border-radius: 999px; background: var(--primary-soft); color: var(--primary-ink); min-width: 78px; text-align: center; }
.timer.warn { background: var(--accent-soft); color: var(--accent); }
.timer.danger { background: var(--danger-soft); color: var(--danger); }
.timer.label { font-family: var(--font); font-size: .9rem; }
@media (hover: none) { .opt:hover { border-color: var(--line-strong); } .opt.sel:hover { border-color: var(--primary); } }
.timebar { height: 4px; background: var(--line); }
.timebar i { display: block; height: 100%; background: var(--primary); transition: width 1s linear, background .3s; }
.overlay-body { flex: 1; overflow-y: auto; -webkit-overflow-scrolling: touch; }
.overlay-body .wrap { padding-top: 18px; padding-bottom: 28px; }
.overlay-foot { background: var(--surface); border-top: 1px solid var(--line); padding: 10px 14px calc(10px + env(safe-area-inset-bottom)); }
.overlay-foot .row { max-width: var(--maxw); margin: 0 auto; display: flex; gap: 8px; }
.overlay-foot .btn { flex: 1; }

.q-progress { display: flex; gap: 6px; margin-bottom: 14px; }
.q-progress i { flex: 1; height: 6px; border-radius: 3px; background: var(--line); }
.q-progress i.done { background: color-mix(in srgb, var(--primary) 45%, var(--line)); }
.q-progress i.cur { background: var(--primary); }
.q-text { font-size: 1.12rem; font-weight: 600; color: var(--text-strong); margin-bottom: 16px; }
.opts { display: grid; gap: 10px; }
.opt {
  display: flex; gap: 12px; align-items: flex-start; text-align: left; width: 100%; min-height: 56px; padding: 14px 16px;
  border: 1.5px solid var(--line-strong); border-radius: var(--radius); background: var(--surface); color: var(--text); cursor: pointer;
  transition: border-color .15s, background .15s; -webkit-tap-highlight-color: transparent;
}
.opt:hover { border-color: var(--primary); }
.opt .key { width: 28px; height: 28px; border-radius: 8px; border: 1.5px solid var(--line-strong); display: grid; place-items: center; font-weight: 700; font-size: .85rem; flex: none; color: var(--muted); }
.opt.sel { border-color: var(--primary); background: var(--primary-soft); }
.opt.sel .key { background: var(--primary); border-color: var(--primary); color: #fff; }
.opt.right { border-color: var(--success); background: var(--success-soft); }
.opt.right .key { background: var(--success); border-color: var(--success); color: #fff; }
.opt.wrong { border-color: var(--danger); background: var(--danger-soft); }
.opt.wrong .key { background: var(--danger); border-color: var(--danger); color: #fff; }
.opt[disabled] { cursor: default; }

.result-hero { text-align: center; padding: 22px 16px; }
.score-ring { width: 132px; height: 132px; margin: 0 auto 12px; position: relative; }
.score-ring svg { width: 100%; height: 100%; transform: rotate(-90deg); }
.score-ring .val { position: absolute; inset: 0; display: grid; place-items: center; font-size: 1.9rem; font-weight: 700; color: var(--text-strong); }
.score-ring .val small { display: block; font-size: .8rem; color: var(--muted); font-weight: 600; margin-top: -6px; }
.save-state { display: inline-flex; align-items: center; gap: 6px; font-size: .85rem; font-weight: 600; padding: 4px 12px; border-radius: 999px; background: var(--surface-2); color: var(--muted); }
.save-state.ok { background: var(--success-soft); color: var(--success); }
.save-state.err { background: var(--danger-soft); color: var(--danger); }
.save-state.pending { background: var(--accent-soft); color: var(--accent); }
.review-item { padding: 14px 16px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); }
.review-item.ok { border-left: 4px solid var(--success); }
.review-item.no { border-left: 4px solid var(--danger); }
.review-item .ans { font-size: .92rem; margin: 6px 0; }
.review-item .exp { font-size: .92rem; color: var(--muted); background: var(--surface-2); border-radius: var(--radius-sm); padding: 10px 12px; margin-top: 8px; }
.encourage { padding: 16px; border-radius: var(--radius); background: var(--info-soft); color: var(--text); }

/* ---------- Hộp thoại ---------- */
.modal-bg { position: fixed; inset: 0; z-index: 200; background: rgba(15, 23, 42, .45); display: flex; align-items: flex-end; justify-content: center; padding: 0; }
@media (min-width: 640px) { .modal-bg { align-items: center; padding: 20px; } }
.modal { width: 100%; max-width: 460px; background: var(--surface); border-radius: 20px 20px 0 0; padding: 22px 20px calc(20px + env(safe-area-inset-bottom)); box-shadow: var(--shadow-lg); max-height: 92vh; overflow-y: auto; }
@media (min-width: 640px) { .modal { border-radius: 20px; } }
.field { display: block; margin-bottom: 14px; }
.field > span { display: block; font-size: .85rem; font-weight: 600; margin-bottom: 6px; }
.input, select.input {
  width: 100%; min-height: 48px; padding: 10px 14px; border-radius: 12px; border: 1.5px solid var(--line-strong);
  background: var(--surface); color: var(--text); font: inherit; font-size: 1rem;
}
.input:focus { outline: none; border-color: var(--primary); box-shadow: 0 0 0 3px var(--primary-soft); }
.input.err { border-color: var(--danger); }
.field-err { color: var(--danger); font-size: .82rem; margin-top: 4px; }
.seg { display: grid; grid-template-columns: 1fr 1fr; gap: 8px; }
.seg label { display: flex; align-items: center; justify-content: center; min-height: 48px; border: 1.5px solid var(--line-strong); border-radius: 12px; cursor: pointer; font-weight: 600; }
.seg input { position: absolute; opacity: 0; pointer-events: none; }
.seg input:checked + label { border-color: var(--primary); background: var(--primary-soft); color: var(--primary-ink); }
.notice { font-size: .78rem; color: var(--muted); line-height: 1.5; }

.menu-list { display: grid; gap: 4px; margin: 8px 0; }
.menu-list button { display: flex; align-items: center; gap: 12px; width: 100%; min-height: 48px; padding: 0 14px; border: 0; background: transparent; border-radius: 12px; color: var(--text); cursor: pointer; text-align: left; font-weight: 500; font-size: .95rem; transition: background .15s; }
.menu-list button:hover { background: var(--surface-2); }
.menu-list button svg { width: 20px; height: 20px; flex: none; color: var(--muted); transition: color .15s; }
.menu-list button:hover svg { color: var(--primary); }

/* Thông báo nhanh */
.toast-wrap { position: fixed; left: 0; right: 0; bottom: calc(84px + env(safe-area-inset-bottom)); z-index: 300; display: grid; justify-items: center; gap: 8px; pointer-events: none; padding: 0 16px; }
.toast { pointer-events: auto; max-width: 520px; background: var(--text-strong); color: var(--bg); padding: 10px 16px; border-radius: 12px; font-size: .9rem; box-shadow: var(--shadow-lg); animation: toastIn .25s ease; }
@keyframes toastIn { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: none; } }

/* Trang chủ */
.chapter-card { display: flex; gap: 14px; align-items: center; padding: 16px; text-decoration: none; color: inherit; }
.chapter-card .no { font-size: 1.3rem; font-weight: 700; color: var(--primary); width: 44px; text-align: center; flex: none; }
.chapter-card .meta { flex: 1; min-width: 0; }
.chapter-card .meta b { display: block; color: var(--text-strong); }

.fade-in { animation: fadeIn .3s ease; }
@keyframes fadeIn { from { opacity: 0; transform: translateY(4px); } to { opacity: 1; transform: none; } }

@media (min-width: 900px) {
  :root { --maxw: 780px; }
  .hero h1 { font-size: 1.9rem; }
}
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: .01ms !important; animation-iteration-count: 1 !important; transition-duration: .01ms !important; scroll-behavior: auto !important; }
}