/* AutoXiv Learn — walkthrough kit
   Grammar borrowed from "Deep Learning, Animated": a dark viewer around a fixed 1280×720 slide,
   navy openers, cream content slides with a full-width interactive stage, then the caption (left)
   beside a dark math card with a plain-words symbol legend and a light "In words" card (right).
   Orange = active / being changed, blue = recorded / reference, green = good, red = bad. */
:root {
  color-scheme: dark;
  --chrome: #F4F2EE; --chrome-2: #FBFAF7; --chrome-3: #EAE9E6; --chrome-ink: #13161C; --chrome-mute: #6D727A;
  --paper: #FBFAF7; --paper-2: #FFFFFF; --card: #FFFFFF; --rule: #DFE1E5; --rule-2: #CED1D6;
  --ink: #13161C; --ink-2: #494D55; --ink-3: #6D727A;
  --navy: #10141A; --navy-2: #1B2028; --navy-ink: #FBFAF7; --navy-mute: #B9BDC5;
  --kick: #285CC2; --kick-on-navy: #6991DC; --say: #285CC2; --say-on-navy: #9DB5F5;
  --q: #E07A2A; --k: #285CC2; --v: #137738; --h: #7B4FB2; --bad: #BE222A; --mask: #9FA3AB;
  --f-display: 'Source Serif 4', 'Source Serif Pro', Charter, Georgia, 'Times New Roman', serif;
  --f-body: 'IBM Plex Sans', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  --f-mono: 'IBM Plex Mono', ui-monospace, 'SFMono-Regular', Menlo, Consolas, monospace;
  --sbw: 248px;
}
* { box-sizing: border-box; }
html, body { height: 100%; }
body { margin: 0; background: var(--chrome); color: var(--chrome-ink); font-family: var(--f-body); font-size: 14px; -webkit-font-smoothing: antialiased; overflow: hidden; }
.mono { font-family: var(--f-mono); font-variant-numeric: tabular-nums; }
button { font-family: inherit; }
a { color: inherit; }
:focus-visible { outline: 2px solid var(--say); outline-offset: 2px; }

/* ---------- app shell ---------- */
#app { display: grid; grid-template-columns: var(--sbw) minmax(0, 1fr); height: 100%; }
#app.sb-collapsed { grid-template-columns: 0 minmax(0, 1fr); }
#sidebar { background: var(--chrome-2); border-right: 1px solid var(--rule); overflow-y: auto; overflow-x: hidden; display: flex; flex-direction: column; min-width: 0; }
#app.sb-collapsed #sidebar { visibility: hidden; }
.sb-home { display: block; padding: 12px 18px 0; font: 500 12px var(--f-body); color: var(--chrome-mute); text-decoration: none; }
.sb-home:hover { color: var(--chrome-ink); }
.sb-brand { padding: 12px 18px 16px; border-bottom: 1px solid var(--chrome-3); }
.sb-brand .kick { font: 600 10.5px/1.4 var(--f-body); letter-spacing: .14em; text-transform: uppercase; color: var(--kick); }
.sb-brand h1 { font: 700 20px/1.15 var(--f-display); margin: 6px 0 0; color: var(--chrome-ink); }
.sb-brand .meta { font: 400 11.5px var(--f-mono); color: var(--chrome-mute); margin-top: 8px; }
.sb-list { list-style: none; margin: 0; padding: 10px 0 16px; }
.sb-list button { width: 100%; background: none; border: 0; color: var(--chrome-mute); text-align: left; padding: 6px 16px 6px 18px; font-size: 13px; line-height: 1.35; cursor: pointer; display: flex; gap: 9px; align-items: flex-start; }
.sb-list button:hover { color: var(--chrome-ink); background: var(--chrome-3); }
.sb-list .dot { flex: 0 0 8px; height: 8px; margin-top: 5px; border-radius: 50%; border: 1.5px solid var(--chrome-mute); }
.sb-list button.seen .dot { background: var(--say); border-color: var(--say); }
.sb-list button.here { color: var(--chrome-ink); background: var(--chrome-3); }
.sb-list button.here .dot { background: var(--kick); border-color: var(--kick); }
.sb-list .num { font: 500 11px var(--f-mono); color: var(--chrome-mute); min-width: 18px; }
.sb-series { padding: 4px 18px 14px; border-top: 1px solid var(--chrome-3); }
.sb-series h4 { font: 600 10.5px var(--f-body); letter-spacing: .14em; text-transform: uppercase; color: var(--chrome-mute); margin: 12px 0 6px; }
.sb-series a { display: block; font-size: 12.5px; line-height: 1.35; color: var(--chrome-mute); text-decoration: none; padding: 3px 0; }
.sb-series a:hover { color: var(--chrome-ink); }
.sb-series a.cur { color: var(--chrome-ink); font-weight: 600; }
.sb-foot { margin-top: auto; padding: 12px 18px 16px; border-top: 1px solid var(--chrome-3); font: 400 11px/1.8 var(--f-mono); color: var(--chrome-mute); }
.kbd { font: 500 10.5px var(--f-mono); border: 1px solid var(--rule-2); border-bottom-width: 2px; border-radius: 4px; padding: 0 4px; color: var(--chrome-ink); }

#viewport { grid-column: 2; position: relative; display: flex; flex-direction: column; min-width: 0; height: 100%; }
#frameHost { position: relative; flex: 1; min-height: 0; overflow: hidden; }
#frame { position: absolute; left: 0; top: 0; width: 1280px; height: 720px; transform-origin: 0 0; border-radius: 6px; box-shadow: 0 6px 24px rgba(20,24,36,.08), 0 0 0 1px var(--rule); overflow: hidden; background: var(--paper); }
#navbar { height: 46px; flex: 0 0 46px; display: flex; align-items: center; gap: 10px; padding: 0 16px; border-top: 1px solid var(--rule); background: var(--chrome-2); }
.nav-btn { background: var(--card); color: var(--chrome-ink); border: 1px solid var(--rule-2); border-radius: 6px; height: 30px; padding: 0 12px; font-size: 13px; cursor: pointer; display: inline-flex; align-items: center; gap: 6px; text-decoration: none; white-space: nowrap; }
.nav-btn:hover { border-color: var(--chrome-mute); }
.nav-btn:disabled { opacity: .4; cursor: default; }
.nav-pos { font: 400 12px var(--f-mono); color: var(--chrome-mute); min-width: 0; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.nav-prog { flex: 1; height: 3px; background: var(--chrome-3); border-radius: 2px; overflow: hidden; min-width: 40px; }
.nav-prog > i { display: block; height: 100%; background: var(--kick); width: 0; transition: width .3s; }

/* ---------- content slides ---------- */
.slide { position: absolute; inset: 0; background: var(--paper); color: var(--ink); color-scheme: light; overflow: hidden; }
.slide.leaving { pointer-events: none; z-index: 0; }
.s-head { position: absolute; left: 72px; right: 72px; top: 30px; }
.kicker { font: 600 12.5px/1 var(--f-body); letter-spacing: .12em; text-transform: uppercase; color: var(--kick); display: flex; gap: 8px; align-items: center; }
.kicker .slide-id { margin-left: auto; font: 400 11px var(--f-mono); letter-spacing: .02em; text-transform: none; color: var(--ink-3); }
.title { font: 700 27px/1.13 var(--f-display); margin: 9px 0 0; text-wrap: balance; max-width: 1136px; letter-spacing: -0.006em; color: var(--ink); }
.stage { position: absolute; left: 72px; right: 72px; top: 124px; height: 330px; background: var(--paper-2); border: 1px solid var(--rule); border-radius: 12px; display: flex; flex-direction: column; overflow: hidden; }
.stage svg.st { display: block; width: 1134px; height: 292px; flex: 0 0 292px; }
.stage .controls { flex: 1 1 auto; min-height: 36px; border-top: 1px solid var(--rule); display: flex; align-items: center; flex-wrap: wrap; gap: 4px 16px; padding: 3px 12px; font-size: 12.5px; color: var(--ink-2); background: var(--card); }
.band { position: absolute; left: 72px; right: 72px; top: 466px; bottom: 16px; display: grid; grid-template-columns: minmax(0, 1fr) 620px; gap: 28px; }
.band-left { display: flex; flex-direction: column; justify-content: space-between; min-width: 0; min-height: 0; gap: 10px; }
.caption { font: 400 16.5px/1.5 var(--f-body); color: var(--ink); margin: 2px 0 0; max-width: 34em; }
.caption b { font-weight: 600; }
.side { display: flex; flex-direction: column; gap: 7px; min-width: 0; min-height: 0; }
.math-card { background: var(--navy); color: var(--navy-ink); border-radius: 8px; padding: 9px 16px 9px; min-width: 0; }
.mc-row { display: flex; align-items: baseline; gap: 12px; }
.mc-prompt { font: 700 17px var(--f-mono); color: var(--q); flex: 0 0 auto; }
.mc-eq { font-size: 16px; overflow-x: auto; overflow-y: hidden; padding: 1px 0 2px; min-width: 0; flex: 1 1 auto; }
.mc-eq .katex-display { margin: 0; text-align: left; }
.mc-eq .katex-display > .katex { text-align: left; }
.mc-legend { margin-top: 6px; padding-top: 6px; border-top: 1px solid rgba(243,240,232,.14); font: 400 11px/1.55 var(--f-mono); color: #BEC2CA; }
.mc-legend .it { display: inline; }
.mc-legend .it + .it::before { content: "  ·  "; color: #646B76; white-space: pre; }
.mc-legend .sym { color: var(--navy-ink); font-size: 12.5px; }
.words-card { background: var(--card); border: 1px solid var(--rule); border-radius: 8px; padding: 8px 16px 9px; display: flex; gap: 14px; align-items: baseline; }
.wc-label { font: 600 12px/1 var(--f-mono); letter-spacing: .1em; color: var(--say); text-transform: uppercase; flex: 0 0 auto; white-space: nowrap; }
.wc-text { font: italic 400 15px/1.45 var(--f-body); color: var(--ink); margin: 0; }
.wc-text .katex { font-style: normal; }
.s-foot { display: flex; justify-content: space-between; align-items: center; gap: 14px; font: 400 13px var(--f-body); color: var(--ink-2); min-width: 0; }
.s-foot .src { white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.s-foot .src a { color: var(--say); }
.deeper-btn { font: 500 13px var(--f-body); color: var(--ink); background: var(--card); border: 1px solid var(--rule-2); border-radius: 999px; padding: 5px 14px; cursor: pointer; white-space: nowrap; }
.deeper-btn:hover { border-color: var(--q); }
.deeper-btn[aria-expanded="true"] { background: var(--navy); color: var(--navy-ink); border-color: var(--navy); }
.deeper-panel { position: absolute; right: 72px; top: 124px; bottom: 52px; width: 700px; background: var(--card); border: 1px solid var(--rule-2); border-radius: 12px; box-shadow: 0 24px 60px rgba(22,33,60,.25); padding: 22px 28px 24px; overflow: auto; opacity: 0; transform: translateY(14px); pointer-events: none; transition: opacity .25s ease, transform .25s ease; z-index: 5; color: var(--ink); }
.deeper-panel.open { opacity: 1; transform: none; pointer-events: auto; }
.deeper-panel .dp-kick { font: 600 11.5px/1 var(--f-body); letter-spacing: .12em; color: var(--kick); text-transform: uppercase; }
.deeper-panel h3 { font: 700 22px/1.2 var(--f-display); margin: 6px 0 12px; }
.deeper-panel h4 { font: 600 11.5px/1.2 var(--f-body); letter-spacing: .12em; text-transform: uppercase; color: var(--ink-3); margin: 18px 0 6px; }
.deeper-panel p, .deeper-panel li { font: 400 14.5px/1.58 var(--f-body); color: var(--ink); max-width: 66ch; }
.deeper-panel ul, .deeper-panel ol { padding-left: 20px; }
.deeper-panel code { font: 13px var(--f-mono); background: var(--paper); padding: 1px 4px; border-radius: 3px; }
.deeper-panel .m-display { margin: 8px 0; overflow-x: auto; overflow-y: hidden; }
.deeper-panel table { border-collapse: collapse; font-size: 13px; margin: 8px 0; }
.deeper-panel td, .deeper-panel th { border-bottom: 1px solid var(--rule); padding: 5px 12px 5px 0; text-align: left; vertical-align: top; }
.deeper-close { position: absolute; right: 14px; top: 10px; border: 0; background: none; font-size: 22px; color: var(--ink-3); cursor: pointer; }

/* ---------- openers and recap (navy) ---------- */
.slide.opener, .slide.recap { background: var(--navy); color: var(--navy-ink); }
.op-wrap { position: absolute; left: 88px; right: 72px; top: 84px; bottom: 70px; display: grid; grid-template-columns: minmax(0, 1fr) 420px; gap: 48px; }
.op-kick { font: 600 13px/1.3 var(--f-body); letter-spacing: .14em; text-transform: uppercase; color: var(--kick-on-navy); }
.op-title { font: 700 54px/1.06 var(--f-display); margin: 14px 0 0; text-wrap: balance; letter-spacing: -0.01em; color: var(--navy-ink); }
.op-blurb { font: 400 18.5px/1.5 var(--f-body); color: var(--navy-mute); max-width: 32em; margin: 20px 0 0; }
.op-blurb b { color: var(--kick-on-navy); font-weight: 500; }
.op-blurb i { color: var(--say-on-navy); font-style: normal; }
.op-boxes { display: flex; flex-direction: column; gap: 8px; margin-top: 24px; max-width: 600px; }
.op-cmd { background: #141922; border: 1px solid #313741; border-radius: 8px; padding: 10px 16px; display: flex; gap: 12px; align-items: baseline; color: var(--navy-ink); font-size: 17px; overflow-x: auto; }
.op-cmd .mc-prompt { color: var(--kick-on-navy); }
.op-say { background: var(--navy-2); border: 1px solid #3A404A; border-radius: 8px; padding: 10px 16px; display: flex; gap: 12px; align-items: baseline; }
.op-say .wc-label { color: var(--say-on-navy); }
.op-say .wc-text { color: var(--navy-ink); font-size: 16px; }
.op-steps { list-style: none; margin: 0; padding: 0 0 0 26px; align-self: center; border-left: 1px solid #3A404A; }
.op-steps li { font: 400 14.5px/1.35 var(--f-body); color: var(--navy-ink); padding: 6px 0 6px 34px; position: relative; }
.op-steps li b { position: absolute; left: 0; top: 7px; font: 500 11.5px var(--f-mono); color: var(--navy-mute); }
.op-steps li button { all: unset; cursor: pointer; }
.op-steps li button:hover { color: #fff; text-decoration: underline; text-underline-offset: 3px; }
.op-steps .ls-head { font: 600 11.5px var(--f-body); letter-spacing: .14em; text-transform: uppercase; color: var(--navy-mute); padding: 0 0 8px; }
.op-meta { font: 400 12.5px var(--f-mono); color: var(--navy-mute); margin-top: 18px; }
.op-hint { position: absolute; left: 88px; bottom: 30px; font: 400 13px var(--f-body); color: var(--navy-mute); }
.op-hint .kbd { color: var(--navy-ink); }

.rc-wrap { position: absolute; left: 88px; right: 72px; top: 70px; bottom: 60px; display: grid; grid-template-columns: minmax(0, 1fr) 470px; gap: 52px; }
.rc-list { list-style: none; padding: 0; margin: 22px 0 0; }
.rc-list li { font: 400 17px/1.5 var(--f-body); color: var(--navy-ink); padding: 0 0 14px 30px; position: relative; max-width: 34em; }
.rc-list li::before { content: "✓"; position: absolute; left: 0; top: 0; color: var(--kick-on-navy); font-weight: 600; }
.rc-check { background: var(--navy-2); border: 1px solid #3A404A; border-radius: 10px; padding: 16px 18px; }
.rc-check h4 { font: 600 11.5px var(--f-body); letter-spacing: .14em; text-transform: uppercase; color: var(--say-on-navy); margin: 0 0 8px; }
.rc-check p.q { font: 400 15.5px/1.5 var(--f-body); color: var(--navy-ink); margin: 0 0 10px; }
.rc-opt { display: block; width: 100%; text-align: left; background: #141922; color: var(--navy-ink); border: 1px solid #3A404A; border-radius: 8px; padding: 8px 12px; margin: 6px 0; font-size: 14px; line-height: 1.4; cursor: pointer; }
.rc-opt:hover { border-color: var(--navy-mute); }
.rc-opt.right { border-color: #4FB27A; background: #133325; }
.rc-opt.wrong { border-color: #D9615A; background: #3A1A1D; }
.rc-why { font: 400 14px/1.5 var(--f-body); color: var(--navy-mute); margin: 10px 0 0; }
.rc-next { display: flex; gap: 10px; margin-top: 16px; flex-wrap: wrap; }
.rc-link { display: inline-flex; flex-direction: column; gap: 3px; text-decoration: none; background: #141922; border: 1px solid #313741; border-radius: 8px; padding: 10px 14px; color: var(--navy-ink); min-width: 200px; flex: 1; }
.rc-link:hover { border-color: var(--kick-on-navy); }
.rc-link small { font: 600 10.5px var(--f-body); letter-spacing: .12em; text-transform: uppercase; color: var(--navy-mute); }
.rc-link span { font: 600 15px/1.3 var(--f-display); }

/* ---------- controls inside the stage ---------- */
.ctl { display: inline-flex; align-items: center; gap: 8px; }
.ctl-label { color: var(--ink-2); white-space: nowrap; }
.ctl-out { font: 500 12px var(--f-mono); color: var(--ink); min-width: 44px; font-variant-numeric: tabular-nums; }
.ctl input[type=range] { -webkit-appearance: none; appearance: none; width: 150px; height: 4px; background: #D1D4D9; border-radius: 2px; margin: 0; }
.ctl input[type=range]::-webkit-slider-thumb { -webkit-appearance: none; appearance: none; width: 15px; height: 15px; border-radius: 50%; background: var(--q); border: 2px solid #fff; box-shadow: 0 0 0 1px var(--q); cursor: pointer; }
.ctl input[type=range]::-moz-range-thumb { width: 12px; height: 12px; border-radius: 50%; background: var(--q); border: 2px solid #fff; box-shadow: 0 0 0 1px var(--q); cursor: pointer; }
.ctl-seg { gap: 0; }
.ctl-seg .ctl-label { margin-right: 8px; }
.seg-btn { border: 1px solid var(--rule-2); background: var(--card); color: var(--ink-2); font-size: 12px; padding: 3px 10px; cursor: pointer; margin-left: -1px; }
.seg-btn:first-of-type { border-radius: 6px 0 0 6px; margin-left: 0; }
.seg-btn:last-of-type { border-radius: 0 6px 6px 0; }
.seg-btn.on { background: var(--navy); color: var(--navy-ink); border-color: var(--navy); position: relative; z-index: 1; }
.btn { border: 1px solid var(--rule-2); background: var(--card); color: var(--ink); font-size: 12.5px; padding: 3px 11px; border-radius: 6px; cursor: pointer; white-space: nowrap; }
.btn:hover { border-color: var(--q); }
.btn.primary { background: var(--navy); color: var(--navy-ink); border-color: var(--navy); }
.btn.reset { color: var(--ink-2); }
.ctl-spacer { flex: 1; }
.readout { font: 500 12px var(--f-mono); color: var(--ink); white-space: nowrap; }

/* ---------- SVG vocabulary ---------- */
svg text { font-family: var(--f-body); }
.grid { stroke: #E2E5EA; stroke-width: 1; }
.axis { stroke: var(--ink-3); stroke-width: 1; }
.tick { font: 400 10px var(--f-mono); fill: var(--ink-3); }
.ax-title { font: 600 11.5px var(--f-body); fill: var(--ink-2); }
.region-label { font: 600 11px var(--f-body); letter-spacing: .1em; fill: var(--ink-3); }
.hit { cursor: pointer; }
.draggable { cursor: grab; }
.draggable:active { cursor: grabbing; }
.fo-tex { font-size: 14px; color: var(--ink); line-height: 1.45; }
.fo-tex .katex { font-size: 1.04em; }
.fo-tex p { margin: 0 0 6px; }

.ax-tip { position: fixed; z-index: 1000; display: none; pointer-events: none; background: #161B24; color: #FBFAF7; font: 400 12px/1.4 var(--f-body); padding: 6px 9px; border-radius: 6px; box-shadow: 0 6px 18px rgba(0,0,0,.3); max-width: 340px; }
.tex-fallback { font-family: var(--f-mono); font-size: .9em; }
.katex { font-size: 1.05em; }

@media (prefers-reduced-motion: reduce) { *, *::before, *::after { transition-duration: 0s !important; animation-duration: 0s !important; } }

/* ---------- narrow screens: reflow the slide instead of shrinking it ---------- */
@media (max-width: 860px) {
  #app { grid-template-columns: 0 minmax(0, 1fr); }
  #sidebar { position: fixed; left: 0; top: 0; bottom: 0; width: min(300px, 86vw); z-index: 60; transform: translateX(-102%); transition: transform .25s; visibility: visible; }
  #app.sb-open #sidebar { transform: none; }
}
body.flow { overflow: auto; }
body.flow #app { height: auto; min-height: 100%; }
body.flow #viewport { height: auto; }
body.flow #frameHost { overflow: visible; padding: 12px 16px 70px; }
body.flow #frame { position: relative; width: 100%; height: auto; transform: none !important; left: auto !important; top: auto !important; }
body.flow .slide { position: relative; inset: auto; min-height: 70vh; padding-bottom: 8px; }
body.flow .slide.leaving { display: none; }
body.flow .s-head, body.flow .stage, body.flow .band { position: relative; left: auto; right: auto; top: auto; bottom: auto; height: auto; }
body.flow .s-head { padding: 18px 16px 0; }
body.flow .title { font-size: 22px; }
body.flow .stage { margin: 14px 16px 0; }
body.flow .stage svg.st { width: 100%; height: auto; flex: none; }
body.flow .band { display: flex; flex-direction: column; padding: 14px 16px; gap: 14px; }
body.flow .caption { font-size: 15px; }
body.flow .s-foot { flex-wrap: wrap; }
body.flow .deeper-panel { position: fixed; left: 8px; right: 8px; top: 8px; bottom: 60px; width: auto; }
body.flow .op-wrap, body.flow .rc-wrap { position: relative; left: auto; right: auto; top: auto; bottom: auto; display: block; padding: 28px 20px 40px; }
body.flow .op-title { font-size: 34px; }
body.flow .op-steps { border-left: 0; padding-left: 0; margin-top: 24px; }
body.flow .op-hint { position: static; padding: 0 20px 20px; }
body.flow .rc-check { margin-top: 22px; }
body.flow #navbar { position: fixed; left: 0; right: 0; bottom: 0; z-index: 40; }
body.flow .nav-pos { display: none; }
body.flow .stage { overflow-x: auto; }
body.flow .stage svg.st { min-width: 640px; }