@font-face { font-family: "IBM Plex Sans"; font-weight: 400; src: url(fonts/ibm-plex-sans-latin-400-normal.woff2) format("woff2"); font-display: swap; }
@font-face { font-family: "IBM Plex Sans"; font-weight: 500; src: url(fonts/ibm-plex-sans-latin-500-normal.woff2) format("woff2"); font-display: swap; }
@font-face { font-family: "IBM Plex Sans"; font-weight: 600; src: url(fonts/ibm-plex-sans-latin-600-normal.woff2) format("woff2"); font-display: swap; }
@font-face { font-family: "IBM Plex Sans"; font-weight: 700; src: url(fonts/ibm-plex-sans-latin-700-normal.woff2) format("woff2"); font-display: swap; }
@font-face { font-family: "IBM Plex Mono"; font-weight: 500; src: url(fonts/ibm-plex-mono-latin-500-normal.woff2) format("woff2"); font-display: swap; }
@font-face { font-family: "IBM Plex Mono"; font-weight: 600; src: url(fonts/ibm-plex-mono-latin-600-normal.woff2) format("woff2"); font-display: swap; }

@font-face { font-family: "IBM Plex Sans"; font-weight: 400; src: url(fonts/ibm-plex-sans-vietnamese-400-normal.woff2) format("woff2"); font-display: swap; unicode-range: U+0102-0103,U+0110-0111,U+0128-0129,U+0168-0169,U+01A0-01A1,U+01AF-01B0,U+0300-0301,U+0303-0304,U+0308-0309,U+0323,U+0329,U+1EA0-1EF9,U+20AB; }
@font-face { font-family: "IBM Plex Sans"; font-weight: 500; src: url(fonts/ibm-plex-sans-vietnamese-500-normal.woff2) format("woff2"); font-display: swap; unicode-range: U+0102-0103,U+0110-0111,U+0128-0129,U+0168-0169,U+01A0-01A1,U+01AF-01B0,U+0300-0301,U+0303-0304,U+0308-0309,U+0323,U+0329,U+1EA0-1EF9,U+20AB; }
@font-face { font-family: "IBM Plex Sans"; font-weight: 600; src: url(fonts/ibm-plex-sans-vietnamese-600-normal.woff2) format("woff2"); font-display: swap; unicode-range: U+0102-0103,U+0110-0111,U+0128-0129,U+0168-0169,U+01A0-01A1,U+01AF-01B0,U+0300-0301,U+0303-0304,U+0308-0309,U+0323,U+0329,U+1EA0-1EF9,U+20AB; }
@font-face { font-family: "IBM Plex Sans"; font-weight: 700; src: url(fonts/ibm-plex-sans-vietnamese-700-normal.woff2) format("woff2"); font-display: swap; unicode-range: U+0102-0103,U+0110-0111,U+0128-0129,U+0168-0169,U+01A0-01A1,U+01AF-01B0,U+0300-0301,U+0303-0304,U+0308-0309,U+0323,U+0329,U+1EA0-1EF9,U+20AB; }
@font-face { font-family: "IBM Plex Mono"; font-weight: 500; src: url(fonts/ibm-plex-mono-vietnamese-500-normal.woff2) format("woff2"); font-display: swap; unicode-range: U+0102-0103,U+0110-0111,U+0128-0129,U+0168-0169,U+01A0-01A1,U+01AF-01B0,U+0300-0301,U+0303-0304,U+0308-0309,U+0323,U+0329,U+1EA0-1EF9,U+20AB; }
@font-face { font-family: "IBM Plex Mono"; font-weight: 600; src: url(fonts/ibm-plex-mono-vietnamese-600-normal.woff2) format("woff2"); font-display: swap; unicode-range: U+0102-0103,U+0110-0111,U+0128-0129,U+0168-0169,U+01A0-01A1,U+01AF-01B0,U+0300-0301,U+0303-0304,U+0308-0309,U+0323,U+0329,U+1EA0-1EF9,U+20AB; }

:root {
  color-scheme: dark;
  --bg: #0b1020;
  --panel: #121a33;
  --panel-2: #172042;
  --line: rgba(255, 255, 255, 0.10);
  --text: #e8ecf5;
  --dim: #8b96b4;
  --accent: #4dd8ff;
  --radius: 18px;
  --sans: "IBM Plex Sans", system-ui, -apple-system, "Segoe UI", sans-serif;
  --mono: "IBM Plex Mono", ui-monospace, "SF Mono", Menlo, monospace;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; background: radial-gradient(1200px 600px at 50% -10%, #17224a 0%, var(--bg) 60%) fixed; color: var(--text); font: 400 16px/1.5 var(--sans); }
.wrap { width: min(1240px, 100% - 32px); margin-inline: auto; }
.sr { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }
a { color: inherit; }

/* header */
.top { padding: 40px 0 8px; }
.brand { display: inline-flex; align-items: center; gap: 12px; font: 700 clamp(28px, 4vw, 44px)/1.1 var(--sans); text-decoration: none; letter-spacing: -0.01em; }
.mark { width: 1.1em; height: 1.1em; border-radius: 22%; box-shadow: 0 0 24px rgba(77, 216, 255, 0.35); }
.tagline { margin: 10px 0 24px; color: var(--dim); font-size: 18px; }
.controls { display: flex; flex-wrap: wrap; gap: 14px 20px; align-items: center; }
.search { flex: 1 1 320px; max-width: 520px; }
.search input { width: 100%; height: 48px; padding: 0 18px; border-radius: 999px; border: 1px solid var(--line); background: var(--panel); color: var(--text); font: 500 16px var(--sans); outline: none; }
.search input::placeholder { color: var(--dim); }
.search input:focus-visible { border-color: var(--accent); box-shadow: 0 0 0 3px rgba(77, 216, 255, 0.25); }
.tabs { display: flex; flex-wrap: wrap; gap: 8px; }
.tab { height: 40px; padding: 0 16px; border-radius: 999px; border: 1px solid var(--line); background: transparent; color: var(--text); font: 600 14px var(--sans); cursor: pointer; display: inline-flex; align-items: center; gap: 8px; }
.tab .dot { width: 9px; height: 9px; border-radius: 50%; background: var(--c, var(--accent)); }
.tab .n { color: var(--dim); font: 600 12px var(--mono); }
.tab:hover { border-color: rgba(255, 255, 255, 0.3); }
.tab[aria-current="true"] { background: var(--c, var(--accent)); border-color: transparent; color: #0b1020; }
.tab[aria-current="true"] .dot { background: #0b1020; }
.tab[aria-current="true"] .n { color: rgba(11, 16, 32, 0.7); }
.tab:focus-visible, .btn:focus-visible, .card:focus-visible, .close:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }
.stats { margin: 16px 0 0; color: var(--dim); font: 500 13px var(--mono); }

/* sections */
main { padding: 8px 0 60px; }
.field { margin-top: 44px; scroll-margin-top: 16px; }
.field-head { display: flex; align-items: baseline; flex-wrap: wrap; gap: 6px 16px; padding-bottom: 12px; border-bottom: 2px solid var(--c); }
.field-head h2 { margin: 0; font: 700 clamp(24px, 3vw, 32px)/1.2 var(--sans); }
.field-head .count { font: 600 13px var(--mono); color: var(--c); }
.field-head p { margin: 0; color: var(--dim); flex-basis: 100%; }
.series { margin-top: 26px; }
.series h3 { margin: 0 0 14px; font: 600 14px var(--mono); letter-spacing: 0.06em; text-transform: uppercase; color: var(--dim); }
.grid { display: grid; gap: 20px; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); }

/* cards */
.card { display: flex; flex-direction: column; text-align: left; padding: 0; border: 1px solid var(--line); border-radius: var(--radius); background: var(--panel); color: inherit; cursor: pointer; overflow: hidden; font: inherit; transition: transform 0.18s ease, border-color 0.18s ease, box-shadow 0.18s ease; }
.card:hover { transform: translateY(-4px); border-color: var(--c); box-shadow: 0 14px 34px rgba(0, 0, 0, 0.35); }
.thumb { position: relative; aspect-ratio: 16 / 9; background: #0e1530; }
.thumb img { width: 100%; height: 100%; object-fit: cover; display: block; }
.play { position: absolute; inset: 0; display: grid; place-items: center; background: linear-gradient(180deg, transparent 50%, rgba(5, 8, 20, 0.65)); opacity: 0; transition: opacity 0.18s; }
.play::before { content: ""; width: 58px; height: 58px; border-radius: 50%; background: var(--c); box-shadow: 0 6px 24px rgba(0, 0, 0, 0.5); }
.play::after { content: ""; position: absolute; border-style: solid; border-width: 11px 0 11px 18px; border-color: transparent transparent transparent #0b1020; margin-left: 4px; }
.card:hover .play, .card:focus-visible .play { opacity: 1; }
.dur { position: absolute; right: 10px; bottom: 10px; padding: 2px 8px; border-radius: 8px; background: rgba(5, 8, 20, 0.85); font: 600 12px var(--mono); }
.seen { position: absolute; left: 10px; top: 10px; padding: 2px 9px; border-radius: 999px; background: rgba(126, 231, 135, 0.92); color: #0b1020; font: 700 11px var(--sans); }
.info { padding: 14px 16px 16px; display: flex; flex-direction: column; gap: 6px; flex: 1; }
.info h4 { margin: 0; font: 700 18px/1.25 var(--sans); }
.info p { margin: 0; color: var(--dim); font-size: 14px; }
.tags { display: flex; flex-wrap: wrap; gap: 6px; margin-top: auto; padding-top: 8px; }
.tag { padding: 1px 9px; border-radius: 999px; background: rgba(255, 255, 255, 0.06); font: 500 12px var(--mono); color: var(--dim); }
.empty { margin: 60px 0; text-align: center; color: var(--dim); font-size: 18px; }
.foot { padding: 28px 0 48px; color: var(--dim); font-size: 14px; border-top: 1px solid var(--line); }

/* modal */
.modal { position: fixed; inset: 0; z-index: 20; display: grid; place-items: center; padding: 16px; }
.modal[hidden] { display: none; }
.modal-backdrop { position: absolute; inset: 0; background: rgba(4, 6, 16, 0.82); backdrop-filter: blur(6px); }
.modal-card { position: relative; display: flex; flex-direction: column; width: min(1100px, 100%, max(480px, calc((100dvh - 300px) * 1.7778))); max-height: calc(100dvh - 32px); overflow: auto; border-radius: 22px; background: var(--panel); border: 1px solid var(--line); box-shadow: 0 30px 80px rgba(0, 0, 0, 0.6); }
.stage { position: relative; flex: 0 1 auto; }
.modal-card video { display: block; flex: 0 1 auto; width: 100%; min-height: 160px; aspect-ratio: 16 / 9; object-fit: contain; background: #000; }
.modal-body { flex: none; padding: 14px 24px 18px; }
/* end of a video: "next up" button over the middle of the picture (the native controls stay clickable below it) */
.up-next { position: absolute; inset: 0 0 52px; display: grid; place-items: center; background: rgba(4, 6, 16, 0.62); pointer-events: none; }
.up-next[hidden] { display: none; }
.up-next-btn { pointer-events: auto; display: flex; flex-direction: column; gap: 4px; max-width: min(520px, 86%); padding: 16px 28px; border-radius: 16px; border: 2px solid var(--c, var(--accent)); background: rgba(11, 16, 32, 0.92); color: var(--text); font: 700 20px/1.25 var(--sans); text-align: center; cursor: pointer; }
.up-next-btn span { font: 600 12px var(--mono); letter-spacing: 0.06em; text-transform: uppercase; color: var(--c, var(--accent)); }
.up-next-btn:hover { background: var(--c, var(--accent)); color: #0b1020; }
.up-next-btn:hover span { color: #0b1020; }
.up-next-btn:focus-visible { outline: 3px solid var(--accent); outline-offset: 3px; }
.crumb { margin: 0 0 6px; font: 600 12px var(--mono); letter-spacing: 0.06em; text-transform: uppercase; color: var(--c, var(--accent)); }
.modal-body h2 { margin: 0 0 6px; font: 700 26px/1.2 var(--sans); }
.modal-body p { margin: 0; color: var(--dim); }
.modal-nav { display: flex; flex-wrap: wrap; align-items: center; gap: 10px; margin-top: 14px; }
.modal-nav .lang { margin-right: auto; }
.btn { height: 40px; padding: 0 16px; border-radius: 999px; border: 1px solid var(--line); background: var(--panel-2); color: var(--text); font: 600 14px var(--sans); cursor: pointer; }
.btn:hover:not(:disabled) { border-color: var(--accent); }
.btn:disabled { opacity: 0.4; cursor: default; }
.close { position: absolute; top: 10px; right: 10px; z-index: 2; width: 40px; height: 40px; border-radius: 50%; border: 0; background: rgba(5, 8, 20, 0.75); color: #fff; font-size: 26px; line-height: 1; cursor: pointer; }
.close:hover { background: rgba(5, 8, 20, 0.95); }

@media (max-width: 600px) {
  .top { padding-top: 24px; }
  .modal-body { padding: 14px 16px 18px; }
  .modal-card { border-radius: 16px; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .card, .card:hover { transition: none; transform: none; }
}

/* language switcher */
.lang { display: inline-flex; gap: 4px; padding: 4px; border: 1px solid var(--line); border-radius: 999px; background: var(--panel); }
.lang button { font: 600 13px/1 var(--mono); padding: 7px 10px; display: inline-flex; align-items: center; border: 0; border-radius: 999px; background: transparent; color: var(--dim); cursor: pointer; }
.lang button[aria-pressed="true"] { background: var(--accent); color: var(--bg); }
.lang button:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }
.top .lang { position: absolute; top: 18px; right: 0; }
.top .wrap { position: relative; }
.langs-on { font: 600 11px/1 var(--mono); letter-spacing: .06em; color: var(--dim); margin-left: 8px; }
.flag { display: inline-flex; width: 26px; height: 18px; border-radius: 3px; overflow: hidden; box-shadow: 0 0 0 1px rgba(255, 255, 255, .25); opacity: .6; transition: opacity .15s; }
.flag svg { width: 100%; height: 100%; display: block; }
.lang button:hover .flag, .lang button[aria-pressed="true"] .flag { opacity: 1; }
.lang button[aria-pressed="true"] { background: var(--accent); }

@media (max-width: 600px) {
  /* no room beside the title: put the switcher on its own row above it */
  .top .lang { position: static; display: flex; width: max-content; margin: 0 0 14px auto; }
  .lang button { min-height: 40px; padding: 0 12px; }
  /* Copy link on its own row, Previous / Next side by side below it */
  .modal-nav { display: grid; grid-template-columns: 1fr 1fr; }
  .modal-nav .btn { height: auto; min-height: 40px; padding: 8px 14px; line-height: 1.25; }
  .modal-nav #share, .modal-nav .lang { grid-column: 1 / -1; }
  .modal-nav .lang { margin: 0; justify-self: start; }
}

/* sub categories under the subject tabs */
.subtabs { margin-top: 10px; }
.subtabs[hidden] { display: none; }
.tab.sub { height: 32px; padding: 0 12px; font-size: 13px; }

/* real links (crawlable URLs) styled like the buttons they replaced */
a.tab, a.card { text-decoration: none; }
.field-head h2 a, .series h3 a { color: inherit; text-decoration: none; }
.field-head h2 a:hover, .series h3 a:hover { text-decoration: underline; }
.transcript { margin-top: 14px; color: var(--dim); }
.transcript summary { cursor: pointer; font: 600 13px var(--mono); letter-spacing: 0.06em; text-transform: uppercase; color: var(--c, var(--accent)); }
.transcript div { margin-top: 10px; display: grid; gap: 8px; max-height: 220px; overflow: auto; }
.transcript p { margin: 0; }
/* static watch page (what crawlers and no-JS visitors get; the app replaces it) */
.watch { max-width: 900px; margin: 32px auto; }
.watch video { width: 100%; aspect-ratio: 16 / 9; background: #000; border-radius: var(--radius); }
.watch h2 { font: 700 clamp(26px, 4vw, 38px)/1.2 var(--sans); margin: 8px 0; }
.watch h3 { margin: 28px 0 10px; font: 600 14px var(--mono); letter-spacing: 0.06em; text-transform: uppercase; color: var(--c); }
.watch .lead { color: var(--dim); font-size: 18px; }
.crumbs { font: 600 13px var(--mono); color: var(--dim); }
.crumbs a { color: var(--c); text-decoration: none; }

/* phones (and short landscape windows): the player fills the screen and the video stays pinned on top
   while the title, transcript and buttons scroll underneath; in landscape the video gets the whole height */
@media (max-width: 600px), (max-height: 500px) {
  .modal { padding: 0; }
  .modal-card { width: 100%; height: 100dvh; max-height: none; border: 0; border-radius: 0; }
  .stage { position: sticky; top: 0; z-index: 1; }
  .modal-card video { aspect-ratio: auto; height: min(56.25vw, 100dvh); object-fit: contain; }
  .close { position: fixed; top: 8px; right: 8px; z-index: 3; }
}
/* portrait phones: park the close button at the bottom right, within thumb reach (the video controls are up top) */
@media (max-width: 600px) and (min-height: 501px) {
  .close { top: auto; right: max(16px, env(safe-area-inset-right)); bottom: max(16px, env(safe-area-inset-bottom)); width: 52px; height: 52px; background: rgba(5, 8, 20, 0.92); border: 1px solid var(--line); box-shadow: 0 6px 20px rgba(0, 0, 0, 0.55); }
  .modal-body { padding-bottom: 88px; }
}

/* interactive examples: /examples/, the Try it block in the player, and the widgets themselves */
.ex-page { max-width: 900px; margin: 32px auto; --c: #7ee787; }
.ex-page h2 { font: 700 clamp(26px, 4vw, 38px)/1.2 var(--sans); margin: 8px 0; }
.ex-page h3 { margin: 28px 0 10px; font: 600 14px var(--mono); letter-spacing: 0.06em; text-transform: uppercase; color: var(--c); }
.ex-lead { color: var(--dim); font-size: 18px; margin: 0 0 16px; }
.ex-grid { display: grid; gap: 16px; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); margin-top: 20px; }
.ex-card { display: flex; flex-direction: column; gap: 6px; padding: 18px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--panel); text-decoration: none; transition: transform 0.18s, border-color 0.18s; }
.ex-card:hover { transform: translateY(-3px); border-color: var(--c); }
.ex-card h3 { margin: 0; font: 700 18px/1.25 var(--sans); letter-spacing: 0; text-transform: none; color: var(--text); }
.ex-card p { margin: 0; color: var(--dim); font-size: 14px; }
.ex-from { margin-top: auto; padding-top: 8px; color: var(--c); font: 600 12px var(--mono); }
.ex-teaser { margin-top: 36px; padding-top: 14px; border-top: 1px solid var(--line); color: var(--dim); }
.ex-teaser summary, .m-ex summary { cursor: pointer; font: 600 13px var(--mono); letter-spacing: 0.06em; text-transform: uppercase; color: #7ee787; }
.ex-teaser[open] summary { margin-bottom: 8px; }
.ex-teaser p { margin: 0 0 10px; }
.ex-links { margin: 0 0 10px; padding-left: 20px; color: var(--dim); }
.ex-links a { color: var(--text); font-weight: 600; }
.m-examples[hidden] { display: none; }
.m-ex { margin-top: 14px; color: var(--dim); }
.m-ex[open] summary { margin-bottom: 4px; }
.m-ex .m-example { margin-top: 12px; }
.m-example { padding: 14px 16px 16px; border: 1px solid var(--line); border-radius: 14px; background: rgba(255, 255, 255, 0.03); --c: #7ee787; }
.m-example h3 { margin: 0 0 4px; font: 600 13px var(--mono); letter-spacing: 0.06em; text-transform: uppercase; color: var(--c); }
.m-example .ex-lead { font-size: 14px; margin-bottom: 12px; }
.example { display: grid; gap: 14px; padding: 18px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--panel); --on: #4dd8ff; }
.m-example .example { padding: 12px; background: transparent; border: 0; }
.ex-row { display: flex; gap: 8px; justify-content: center; flex-wrap: wrap; }
.ex-sw { display: grid; justify-items: center; gap: 6px; width: 64px; padding: 8px 0; border: 1px solid var(--line); border-radius: 12px; background: var(--panel-2); color: var(--text); cursor: pointer; font: 600 14px var(--mono); }
.ex-sw:focus-visible, .ex-card:focus-visible, .ex-fields input:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }
.ex-place { color: var(--dim); }
.ex-track { position: relative; width: 44px; height: 24px; border-radius: 999px; border: 2px solid var(--dim); }
.ex-knob { position: absolute; top: 2px; left: 2px; width: 16px; height: 16px; border-radius: 50%; background: var(--dim); transition: transform 0.15s; }
.ex-sw[aria-checked="true"] { border-color: var(--on); background: rgba(77, 216, 255, 0.12); }
.ex-sw[aria-checked="true"] .ex-track { border-color: var(--on); }
.ex-sw[aria-checked="true"] .ex-knob { background: var(--on); transform: translateX(20px); }
.ex-digit { font-size: 20px; }
.ex-sw[aria-checked="true"] .ex-digit { color: #ffd166; }
.ex-result { display: flex; gap: 40px; justify-content: center; }
.ex-result > div { display: grid; justify-items: center; }
.ex-cap { display: block; color: var(--dim); font: 600 12px var(--mono); letter-spacing: 0.06em; text-transform: uppercase; }
.ex-big { font: 700 48px/1.2 var(--mono); color: #ffd166; }
.ex-letter.dim { color: var(--dim); }
.ex-note { margin: 0; text-align: center; color: var(--dim); font: 500 16px var(--mono); }
.ex-actions { display: flex; gap: 10px; justify-content: center; flex-wrap: wrap; }
.ex-fields { display: flex; flex-wrap: wrap; gap: 14px; align-items: end; }
.ex-fields label, label.ex-fields { display: grid; gap: 6px; }
.ex-fields input { height: 48px; padding: 0 14px; width: 100%; min-width: 180px; border-radius: 12px; border: 1px solid var(--line); background: var(--bg); color: var(--text); font: 600 20px var(--mono); }
.ex-eq { font: 700 28px var(--mono); color: var(--dim); padding-bottom: 8px; }
.ex-err { margin: 0; min-height: 1.4em; color: #ff6b6b; font-size: 14px; }
.ex-places { display: grid; grid-template-columns: repeat(8, 1fr); gap: 6px; max-width: 560px; margin-inline: auto; width: 100%; }
.ex-cell { text-align: center; padding: 6px 0; color: var(--dim); font: 600 14px var(--mono); }
.ex-bitcell { border: 1px solid var(--line); border-radius: 8px; font-size: 22px; color: var(--dim); }
.ex-bitcell.on { color: #ffd166; border-color: #ffd166; background: rgba(255, 209, 102, 0.12); }
.ex-table { border-collapse: collapse; width: 100%; font: 500 16px var(--mono); }
.ex-table th { text-align: left; color: var(--dim); font: 600 12px var(--mono); letter-spacing: 0.06em; text-transform: uppercase; padding: 6px 10px; }
.ex-table td { padding: 8px 10px; border-top: 1px solid var(--line); }
.ex-table .ex-ch { font-size: 22px; font-weight: 700; color: #4dd8ff; }
.ex-table .ex-mono { color: #ffd166; letter-spacing: 0.1em; }
.ex-table .bad td { color: var(--dim); }
.ex-details summary { cursor: pointer; color: var(--dim); font: 600 13px var(--mono); }
.ex-ascii { margin-top: 10px; display: grid; grid-template-columns: repeat(auto-fill, minmax(78px, 1fr)); gap: 6px; font: 500 14px var(--mono); }
.ex-acell { padding: 4px 8px; border: 1px solid var(--line); border-radius: 8px; color: var(--dim); }
.ex-acell b { color: #4dd8ff; }
@media (max-width: 600px) {
  .ex-sw { width: 40px; font-size: 12px; }
  .ex-track { width: 28px; }
  .ex-sw[aria-checked="true"] .ex-knob { transform: translateX(8px); }
  .ex-result { gap: 24px; }
}
.ex-chans { display: grid; gap: 10px; max-width: 640px; margin-inline: auto; width: 100%; }
.ex-chan { display: grid; grid-template-columns: 70px 1fr 64px auto; gap: 12px; align-items: center; }
.ex-chan input[type="range"] { width: 100%; }
.ex-num { font: 700 18px var(--mono); color: #ffd166; text-align: right; }
.ex-mono { font: 600 16px var(--mono); color: #ffd166; letter-spacing: 0.1em; }
.ex-swatch { height: 120px; border-radius: var(--radius); border: 1px solid var(--line); }
.ex-hex { height: 48px; padding: 0 14px; width: 180px; border-radius: 12px; border: 1px solid var(--line); background: var(--bg); color: var(--text); font: 600 20px var(--mono); }
.ex-code, .ex-code-line { display: block; margin: 0; padding: 10px 14px; border-radius: 10px; background: var(--bg); border: 1px solid var(--line); color: #4dd8ff; font: 500 16px/1.5 var(--mono); white-space: pre-wrap; }
.ex-code-line { display: inline-block; padding: 12px 14px; }
.ex-bm-stage { display: flex; justify-content: center; overflow-x: auto; padding: 6px 0; }
.ex-bm-margin { background: rgba(224, 138, 90, 0.18); outline: 2px dashed #e08a5a; width: max-content; }
.ex-bm-border { border: 4px solid #ffd166; background: rgba(126, 231, 135, 0.22); }
.ex-bm-content { width: 160px; height: 70px; display: grid; place-items: center; background: rgba(77, 216, 255, 0.35); font: 700 22px var(--sans); }
.ex-legend { display: flex; gap: 16px; justify-content: center; flex-wrap: wrap; font: 600 13px var(--mono); }
.ex-key::before { content: ""; display: inline-block; width: 12px; height: 12px; margin-right: 6px; border-radius: 3px; background: var(--k); }
.ex-flex { --i0: #ffd166; --i1: #7ee787; --i2: #ff6b6b; --i3: #4dd8ff; --i4: #d2a8ff; min-height: 240px; border: 2px dashed #4dd8ff; border-radius: 12px; padding: 8px; overflow: auto; }
.ex-fitem { min-width: 64px; display: grid; place-items: center; border-radius: 10px; color: #1a1f33; font: 700 22px var(--mono); flex: 0 0 64px; }
.ex-props { display: grid; gap: 10px; }
.ex-prop { display: grid; gap: 6px; }
.ex-left { justify-content: flex-start; }
.ex-opt { height: 34px; padding: 0 12px; font: 600 13px var(--mono); }
.ex-opt[aria-pressed="true"] { border-color: #ffd166; background: rgba(255, 209, 102, 0.14); color: #ffd166; }
.ex-ta { width: 100%; padding: 12px 14px; border-radius: 12px; border: 1px solid var(--line); background: var(--bg); color: var(--text); font: 500 16px/1.5 var(--mono); resize: vertical; }
.ex-status { margin: 0; font: 600 16px var(--mono); }
.ex-status.good { color: #7ee787; }
.ex-status.bad { color: #ff6b6b; }
.ex-sub { margin: 4px 0 0; color: var(--dim); font: 600 12px var(--mono); letter-spacing: 0.06em; text-transform: uppercase; }
.ex-term { margin: 0; height: 240px; overflow: auto; padding: 12px 14px; border-radius: 10px; background: #05080f; border: 1px solid var(--line); color: var(--text); font: 500 15px/1.5 var(--mono); white-space: pre-wrap; }
.ex-gfiles { display: grid; gap: 8px; }
.ex-gfile { display: grid; grid-template-columns: 1fr auto auto auto; gap: 10px; align-items: center; padding: 8px 12px; border: 1px solid var(--line); border-radius: 12px; }
.ex-gfile.modified { border-color: #ffd166; }
.ex-gfile.staged { border-color: #7ee787; }
.ex-gname { font: 600 16px var(--mono); }
.ex-gbadge { color: var(--dim); font: 600 12px var(--mono); text-transform: uppercase; }
.ex-gfile .btn { height: 34px; padding: 0 12px; font-size: 13px; }
.ex-msg { height: 40px; padding: 0 12px; width: min(340px, 100%); border-radius: 12px; border: 1px solid var(--line); background: var(--bg); color: var(--text); font: 500 15px var(--mono); }
.ex-cols { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }
.ex-tree { display: grid; gap: 4px; justify-items: start; margin-top: 6px; }
.ex-tnode { padding: 4px 10px; border-radius: 8px; border: 1px solid transparent; background: transparent; color: #4dd8ff; font: 600 15px var(--mono); cursor: pointer; }
.ex-tnode.on { border-color: #ffd166; background: rgba(255, 209, 102, 0.14); color: #ffd166; }
.ex-prev { margin-top: 6px; padding: 12px 16px 16px; border-radius: 12px; background: #f4f6fb; color: #1a1f33; min-height: 170px; }
.ex-prev h1 { margin: 6px 0; font: 700 28px var(--sans); }
.ex-prev p { margin: 6px 0 12px; }
.ex-tab { margin: -12px -16px 8px; padding: 4px 16px; background: #dfe6f5; color: #586080; font: 600 12px var(--mono); border-radius: 12px 12px 0 0; }
.ex-ck { display: inline-flex; gap: 6px; align-items: center; font: 600 14px var(--mono); }
.example select { height: 40px; padding: 0 10px; border-radius: 10px; border: 1px solid var(--line); background: var(--bg); color: var(--text); font: 500 15px var(--mono); }
.ex-lanes { display: grid; gap: 8px; }
.ex-lane { padding: 10px 14px; border: 1px solid var(--line); border-radius: 12px; color: var(--dim); font: 600 14px var(--mono); }
.ex-lane.on { border-color: #ffd166; background: rgba(255, 209, 102, 0.14); color: #ffd166; }
.ex-checks { display: grid; gap: 8px; }
.ex-check { display: flex; gap: 10px; align-items: flex-start; padding: 8px 12px; border: 1px solid var(--line); border-radius: 12px; cursor: pointer; }
.ex-check input { margin-top: 4px; width: 18px; height: 18px; }
.ex-check .ex-cap { display: inline; margin-right: 4px; }
@media (max-width: 600px) {
  .ex-chan { grid-template-columns: 56px 1fr 52px; }
  .ex-chan .ex-mono { grid-column: 2 / -1; }
  .ex-cols { grid-template-columns: 1fr; }
  .ex-gfile { grid-template-columns: 1fr auto; }
}

/* home entry points, and the course path (numbered steps, start link, previous / next) */
.collections { display: grid; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); gap: 16px; margin-top: 28px; }
.collection { display: flex; flex-direction: column; gap: 8px; padding: 20px; border: 1px solid var(--line); border-top: 3px solid var(--c); border-radius: var(--radius); background: var(--panel); text-decoration: none; transition: transform 0.18s ease, border-color 0.18s ease; }
.collection:hover { transform: translateY(-3px); border-color: var(--c); }
.collection:focus-visible, .start:focus-visible, .path-nav a:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }
.collection h3 { margin: 0; font: 700 22px/1.2 var(--sans); }
.collection p { margin: 0; color: var(--dim); font-size: 15px; flex: 1; }
.collection .count { color: var(--c); font: 600 13px var(--mono); }
.step { display: inline-grid; place-items: center; min-width: 1.6em; height: 1.6em; margin-right: 8px; padding: 0 4px; border-radius: 999px; background: var(--c); color: #0b1020; font: 700 12px var(--mono); vertical-align: 2px; }
.start { display: inline-block; margin-top: 4px; padding: 8px 16px; border-radius: 999px; background: var(--c); color: #0b1020; font: 700 14px var(--sans); text-decoration: none; }
.start:hover { filter: brightness(1.1); }
.field-head .start { flex-basis: auto; }
.path-nav { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 12px; margin-top: 16px; }
.path-nav a { padding: 10px 16px; border: 1px solid var(--line); border-radius: 999px; background: var(--panel-2); text-decoration: none; font: 600 14px var(--sans); }
.path-nav a:hover { border-color: var(--c); }

/* workbook-style Q&A examples (web/js/examples/workbook-view.js) */
.wb { display: grid; gap: 16px; }
.wb-score { margin: 0; text-align: center; font: 700 22px var(--mono); color: #ffd166; }
.wb-q { display: grid; gap: 10px; padding: 18px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--panel); }
.wb-q header { display: flex; align-items: center; gap: 10px; }
.wb-n { font: 700 14px var(--mono); color: #7ee787; }
.wb-topic { font: 600 12px var(--mono); letter-spacing: 0.06em; text-transform: uppercase; color: var(--dim); }
.wb-mark { margin-left: auto; font: 700 18px var(--mono); color: #ffd166; }
.wb-text { margin: 0; font: 600 20px/1.35 var(--sans); }
.wb-vi { margin: 0; color: #f2c879; font-size: 16px; }
.wb-no-vi .wb-vi { display: none; }
.wb-box { width: 100%; padding: 12px 14px; border-radius: 12px; border: 1px solid var(--line); background: var(--bg); color: var(--text); font: 500 16px/1.4 var(--sans); resize: vertical; }
.wb-box:focus-visible, .wb-points input:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }
.wb-q > .btn { justify-self: start; }
.wb-answer[hidden] { display: none; }
.wb-answer { padding: 12px 14px; border: 1px solid #7ee787; border-radius: 12px; background: rgba(126, 231, 135, 0.06); }
.wb-points { list-style: none; margin: 0; padding: 0; display: grid; gap: 10px; }
.wb-points label { display: flex; gap: 12px; align-items: flex-start; cursor: pointer; }
.wb-points input { width: 22px; height: 22px; margin-top: 2px; accent-color: #7ee787; flex: none; }
.wb-points .wb-en { display: block; font-weight: 600; }
.wb-points .wb-vi { display: block; font-size: 14px; }

/* vocabulary trainer (web/js/examples/vocab-view.js) */
.vt { display: grid; gap: 16px; }
.vt-sum { display: flex; gap: 10px; flex-wrap: wrap; justify-content: center; }
.vt-stat { display: grid; justify-items: center; min-width: 96px; padding: 10px 14px; border: 1px solid var(--line); border-radius: 12px; background: var(--panel); }
.vt-stat b { font: 700 28px var(--mono); color: #ffd166; }
.vt-bi { display: inline-flex; flex-direction: column; gap: 2px; }
.vt-vi { color: #f2c879; font-size: 0.85em; }
.vt-clue { color: var(--dim); font-size: 0.9em; }
.vt-body { display: grid; gap: 14px; justify-items: center; }
.vt-card { width: 100%; display: grid; gap: 12px; padding: 20px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--panel); }
.vt-kind { font: 600 13px var(--mono); letter-spacing: 0.04em; text-transform: uppercase; color: var(--dim); }
.vt-meaning { font: 700 34px/1.2 var(--sans); color: #f2c879; }
.vt-say { font: 500 17px var(--mono); color: var(--dim); }
.vt-text { margin: 0; font: 600 22px/1.4 var(--sans); }
.vt-big { display: flex; align-items: center; gap: 12px; font: 700 40px/1.1 var(--sans); }
.vt-play, .vt-listen { font-size: 20px; }
.vt-input { width: 100%; height: 52px; padding: 0 14px; border-radius: 12px; border: 1px solid var(--line); background: var(--bg); color: var(--text); font: 600 22px var(--mono); }
textarea.vt-input { height: auto; padding: 10px 14px; font: 500 17px/1.4 var(--sans); }
.vt-input:focus-visible, .vt .btn:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }
.vt-feedback.good { border-left: 4px solid #7ee787; padding-left: 12px; }
.vt-feedback.bad { border-left: 4px solid #ff6b6b; padding-left: 12px; }
.vt-correct { margin: 4px 0; font: 700 30px var(--mono); color: #7ee787; }
.vt-q { margin: 0 0 6px; font-weight: 700; }
.vt-word { display: grid; gap: 6px; margin-top: 8px; padding: 14px; border: 1px solid var(--line); border-radius: 12px; background: var(--panel-2); }
.vt-word p { margin: 0; }
.vt-ex { color: var(--dim); }
.vt-missed { margin: 0; padding-left: 20px; text-align: left; }
.vt-start { font-size: 18px; }
.vt-next { justify-self: start; }

/* "Check yourself" (web/js/examples/check-view.js) */
.ck-gap { width: 9em; margin: 0 6px; padding: 4px 10px; border-radius: 10px; border: 1px solid var(--line); background: var(--bg); color: var(--text); font: 600 18px var(--mono); }
.ck-gap:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }
.ck-steps { list-style: decimal; margin: 0; padding-left: 28px; display: grid; gap: 8px; }
.ck-steps li { display: flex; gap: 8px; align-items: center; }
.ck-step { flex: 1; display: grid; }
.ck-ok { color: #7ee787; font-weight: 700; }
.ck-no { color: #ff6b6b; font-weight: 700; }