/* =========================================================
   Chương 4 · Hạt tải dư — deck styles
   Canvas: 1920 × 1080, scaled to fit.
   ========================================================= */

@property --accent { syntax: '<color>'; inherits: true; initial-value: #9ad8ff; }

:root {
  --font-display: 'Bricolage Grotesque', 'Be Vietnam Pro', system-ui, sans-serif;
  --font-body: 'Be Vietnam Pro', system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'JetBrains Mono', ui-monospace, 'SF Mono', Menlo, Consolas, monospace;
  --ease-out: cubic-bezier(.16, 1, .3, 1);
  --ease-io: cubic-bezier(.65, 0, .35, 1);
  --ease-back: cubic-bezier(.34, 1.56, .64, 1);
  /* opener colours: same in both themes (dark ink on bright fill) */
  --op0: #9ad8ff; --op1: #ffc23d; --op2: #ff7a59; --op3: #b49cff; --op4: #45e0a0; --op5: #9ad8ff;
  --ink: #0b0b10;
}

/* ---------- Dark theme (default) ---------- */
:root, :root[data-theme="dark"] {
  color-scheme: dark;
  --bg: #07080d;
  --bg-2: #0e1019;
  --panel: rgba(255, 255, 255, .035);
  --panel-2: rgba(255, 255, 255, .065);
  --line: rgba(255, 255, 255, .09);
  --line-2: rgba(255, 255, 255, .2);
  --grid: rgba(255, 255, 255, .035);
  --text: #f1f2f7;
  --text-2: #c9cedb;
  --muted: #8b93a8;
  --e: #45c8ff;
  --h: #ff4f8b;
  --ph: #ffc23d;
  --heat: #ff8a3d;
  --good: #3ddc97;
  --bad: #ff5d5d;
  --p0: #9ad8ff; --p1: #ffc23d; --p2: #ff7a59; --p3: #b49cff; --p4: #45e0a0; --p5: #9ad8ff;
  --shadow: 0 30px 80px -30px rgba(0, 0, 0, .8);
}

/* ---------- Light theme (for bright rooms / weak projectors) ---------- */
:root[data-theme="light"] {
  color-scheme: light;
  --bg: #f4f1ea;
  --bg-2: #ebe6db;
  --panel: rgba(20, 20, 35, .04);
  --panel-2: rgba(20, 20, 35, .075);
  --line: rgba(20, 20, 35, .12);
  --line-2: rgba(20, 20, 35, .26);
  --grid: rgba(20, 20, 35, .05);
  --text: #12141c;
  --text-2: #2a2f3e;
  --muted: #5d6476;
  --e: #0877b8;
  --h: #d0285f;
  --ph: #b97c00;
  --heat: #d2601a;
  --good: #0c8f5f;
  --bad: #cc3434;
  --p0: #0a6fb0; --p1: #c08400; --p2: #d9482a; --p3: #6a48dd; --p4: #0c8f5f; --p5: #0a6fb0;
  --shadow: 0 30px 70px -35px rgba(40, 30, 10, .35);
}

*, *::before, *::after { box-sizing: border-box; }
html, body { margin: 0; height: 100%; background: var(--bg); color: var(--text); overflow: hidden; }
body { font-family: var(--font-body); -webkit-font-smoothing: antialiased; text-rendering: optimizeLegibility; -webkit-tap-highlight-color: transparent; }
body.idle, body.idle * { cursor: none !important; }
button { font: inherit; color: inherit; }
kbd { font: 600 .85em var(--font-mono); padding: .15em .5em; border-radius: 6px; border: 1px solid var(--line-2); background: var(--panel-2); color: var(--text); }

/* ---------- Stage ---------- */
#viewport { position: fixed; inset: 0; overflow: hidden; background: var(--bg); }
#stage {
  position: absolute; left: 50%; top: 50%; width: 1920px; height: 1080px;
  transform: translate(-50%, -50%); transform-origin: 50% 50%;
  overflow: hidden; background: var(--bg); --accent: var(--p0);
  transition: --accent .9s ease;
}
#stage[data-part="1"] { --accent: var(--p1); }
#stage[data-part="2"] { --accent: var(--p2); }
#stage[data-part="3"] { --accent: var(--p3); }
#stage[data-part="4"] { --accent: var(--p4); }
#stage[data-part="5"] { --accent: var(--p5); }

#ambient { position: absolute; inset: 0; pointer-events: none; z-index: 0; }
.amb-glow { position: absolute; inset: -10%;
  background:
    radial-gradient(38% 42% at 90% 4%, color-mix(in oklab, var(--accent) 17%, transparent), transparent 72%),
    radial-gradient(34% 40% at 2% 104%, color-mix(in oklab, var(--accent) 11%, transparent), transparent 72%);
}
.amb-grid { position: absolute; inset: 0;
  background-image: linear-gradient(var(--grid) 1px, transparent 1px), linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: 80px 80px; background-position: -1px -1px;
  -webkit-mask-image: radial-gradient(ellipse 75% 70% at 50% 45%, #000 25%, transparent 80%);
          mask-image: radial-gradient(ellipse 75% 70% at 50% 45%, #000 25%, transparent 80%);
}
.amb-noise { position: absolute; inset: 0; opacity: .05; mix-blend-mode: overlay;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='220' height='220'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='.85' numOctaves='3' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
}
:root[data-theme="light"] .amb-noise { opacity: .07; mix-blend-mode: multiply; }

.slides { position: absolute; inset: 0; z-index: 1; }
.slide { position: absolute; inset: 0; visibility: hidden; --accent: var(--p0); --op: var(--op0); }
.slide.is-active, .slide.is-leaving { visibility: visible; }
.slide.is-leaving { z-index: 1; pointer-events: none; }
.slide.is-active { z-index: 2; }
.slide[data-part="1"] { --accent: var(--p1); --op: var(--op1); }
.slide[data-part="2"] { --accent: var(--p2); --op: var(--op2); }
.slide[data-part="3"] { --accent: var(--p3); --op: var(--op3); }
.slide[data-part="4"] { --accent: var(--p4); --op: var(--op4); }
.slide[data-part="5"] { --accent: var(--p5); --op: var(--op5); }
.slide .notes { display: none; }
.slide.no-anim, .slide.no-anim * { transition: none !important; }

/* ---------- Chrome ---------- */
#chrome { position: absolute; inset: 0; z-index: 6; pointer-events: none; transition: opacity .5s ease; }
#chrome.off .topbar, #chrome.off .stepdots { opacity: 0; transform: translateY(-10px); }
.topbar { position: absolute; left: 120px; right: 120px; top: 34px; display: flex; align-items: center; justify-content: space-between;
  font: 500 17px/1 var(--font-mono); letter-spacing: .13em; text-transform: uppercase; color: var(--muted); transition: opacity .5s, transform .5s; }
.tb-left, .tb-right { display: flex; align-items: center; gap: 16px; }
.tb-dot { width: 10px; height: 10px; border-radius: 50%; background: var(--accent); box-shadow: 0 0 0 5px color-mix(in oklab, var(--accent) 18%, transparent); }
.tb-part { color: var(--text-2); }
.tb-who { display: inline-flex; align-items: center; gap: 12px; text-transform: none; letter-spacing: 0; font: 500 20px/1 var(--font-body); color: var(--text-2); }
.tb-sep { width: 1px; height: 22px; background: var(--line-2); }
.tb-num { font-variant-numeric: tabular-nums; }
.tb-num b { color: var(--text); font-weight: 600; }
.av { width: 36px; height: 36px; border-radius: 50%; display: inline-grid; place-items: center; background: var(--accent); color: var(--ink);
  font: 800 18px/1 var(--font-display); letter-spacing: 0; flex: none; }
.progress { position: absolute; left: 0; right: 0; bottom: 0; height: 5px; display: flex; gap: 3px; }
.progress .seg { position: relative; overflow: hidden; background: var(--line); }
.progress .seg i { position: absolute; inset: 0; transform-origin: left center; transform: scaleX(var(--f, 0)); background: var(--c); transition: transform .7s var(--ease-out); }
.stepdots { position: absolute; right: 120px; bottom: 30px; display: flex; gap: 8px; transition: opacity .4s; }
.stepdots i { width: 8px; height: 8px; border-radius: 50%; background: var(--line-2); transition: background .3s, transform .3s; }
.stepdots i.on { background: var(--accent); transform: scale(1.15); }

/* ---------- Wipe overlay ---------- */
#wipe { position: absolute; inset: 0; z-index: 30; pointer-events: none; }
#wipe i { position: absolute; inset: 0; transform: translateX(101%); will-change: transform; }
#wipe .w1 { background: var(--bg-2); }
#wipe .w2 { background: var(--wc, var(--op1)); }
#wipe i.w3 { background: color-mix(in oklab, var(--wc, var(--op1)) 55%, #fff); width: 16px; inset: 0 auto 0 0; transform: translateX(1960px); }

/* ---------- Header / body ---------- */
.hd { position: absolute; left: 120px; right: 120px; top: 100px; }
.kicker { display: flex; align-items: center; gap: 16px; font: 500 20px/1 var(--font-mono); letter-spacing: .16em; text-transform: uppercase; color: var(--accent); }
.kicker::before { content: ""; width: 40px; height: 2px; background: currentColor; }
.kicker .ext { margin-left: 10px; padding: 6px 12px; border-radius: 999px; border: 1px solid currentColor; font-size: 16px; letter-spacing: .12em; }
.title { margin: 22px 0 0; font: 700 64px/1.08 var(--font-display); letter-spacing: -.022em; color: var(--text); text-wrap: balance; max-width: 1680px; }
.title .en, .title-en { font: 400 30px/1 var(--font-body); letter-spacing: 0; color: var(--muted); }
.title .en { margin-left: 14px; vertical-align: .32em; white-space: nowrap; }
.title em { font-style: normal; color: var(--accent); }
.bd { position: absolute; left: 120px; right: 120px; top: 290px; bottom: 100px; }
.bd.hi { top: 250px; }
.bd.lo { top: 320px; }

/* ---------- Typography ---------- */
.lead { margin: 0; font: 400 36px/1.5 var(--font-body); color: var(--text-2); }
.lead b, .lead strong, .pts b, .card b, .callout b { color: var(--text); font-weight: 600; }
.big { font: 600 44px/1.3 var(--font-body); color: var(--text); }
.small { font-size: 26px; line-height: 1.45; color: var(--muted); }
.en { color: var(--muted); font-weight: 400; }
.mono { font-family: var(--font-mono); }
.t-e { color: var(--e); } .t-h { color: var(--h); } .t-ph { color: var(--ph); } .t-heat { color: var(--heat); }
.t-ac { color: var(--accent); } .t-good { color: var(--good); } .t-bad { color: var(--bad); } .t-mu { color: var(--muted); } .t-tx { color: var(--text); }
.nowrap { white-space: nowrap; }

.pts { list-style: none; margin: 0; padding: 0; display: flex; flex-direction: column; gap: 30px; }
.pts > li { position: relative; padding-left: 70px; font: 400 33px/1.42 var(--font-body); color: var(--text-2); }
.pts > li::before { content: attr(data-n); position: absolute; left: 0; top: -1px; width: 48px; height: 48px; border-radius: 14px; display: grid; place-items: center;
  font: 600 21px/1 var(--font-mono); color: var(--accent); background: color-mix(in oklab, var(--accent) 13%, transparent); border: 1px solid color-mix(in oklab, var(--accent) 40%, transparent); }
.pts.tight { gap: 22px; }
.pts.sm > li { font-size: 29px; padding-left: 62px; }
.pts.sm > li::before { width: 42px; height: 42px; font-size: 18px; border-radius: 12px; }

/* ---------- Components ---------- */
.card { position: relative; background: var(--panel); border: 1px solid var(--line); border-radius: 26px; padding: 34px 38px; }
.card h3 { margin: 0 0 12px; font: 700 34px/1.18 var(--font-display); letter-spacing: -.01em; color: var(--text); }
.card p { margin: 0; font: 400 28px/1.45 var(--font-body); color: var(--text-2); }
.card .tag { margin-bottom: 16px; display: block; }
.card.ac { border-color: color-mix(in oklab, var(--accent) 45%, transparent); background: color-mix(in oklab, var(--accent) 7%, transparent); }
.tag { font: 600 17px/1 var(--font-mono); letter-spacing: .16em; text-transform: uppercase; color: var(--accent); }
.chip { display: inline-flex; align-items: center; gap: 10px; padding: 10px 18px; border-radius: 999px; border: 1px solid var(--line-2); background: var(--panel);
  font: 500 24px/1.2 var(--font-body); color: var(--text-2); }
.chip b { color: var(--text); font-weight: 600; }
.chip .dot { width: 12px; height: 12px; border-radius: 50%; background: var(--accent); }
.callout { position: relative; padding: 28px 36px; border-radius: 22px; background: color-mix(in oklab, var(--accent) 9%, transparent);
  border: 1px solid color-mix(in oklab, var(--accent) 38%, transparent); font: 400 31px/1.45 var(--font-body); color: var(--text); }
.callout .tag { display: block; margin-bottom: 12px; }
.callout.plain { background: var(--panel); border-color: var(--line-2); }
.term { position: relative; padding: 24px 30px 26px; border-radius: 20px; border: 1px dashed color-mix(in oklab, var(--accent) 55%, transparent); background: var(--panel); }
.term .tag::before { content: "◆ "; }
.term .tw { display: block; margin: 12px 0 8px; font: 700 32px/1.2 var(--font-display); color: var(--text); }
.term .tw i { font: italic 400 24px var(--font-body); color: var(--muted); margin-left: 8px; }
.term p { margin: 0; font: 400 26px/1.45 var(--font-body); color: var(--text-2); }
.arrow-r { display: inline-block; color: var(--accent); margin: 0 10px; }

/* formula boxes */
.M { font-size: 38px; color: var(--text); line-height: 1.2; }
.M.lg { font-size: 46px; } .M.xl { font-size: 56px; } .M.sm { font-size: 32px; } .M.xs { font-size: 27px; }
.M .katex-display { margin: 0; }
.M .katex-display > .katex { text-align: left; }
.M.c .katex-display > .katex { text-align: center; }
.katex { font-size: 1.12em; }
.fx { display: inline-block; padding: 22px 34px; border-radius: 22px; background: var(--panel); border: 1px solid var(--line-2); }
.fx.key { border: 2px solid var(--accent); background: color-mix(in oklab, var(--accent) 7%, var(--bg));
  box-shadow: 0 0 0 8px color-mix(in oklab, var(--accent) 10%, transparent), 0 30px 80px -30px color-mix(in oklab, var(--accent) 55%, transparent); }
.fx-lbls { display: flex; justify-content: space-around; gap: 20px; margin-top: 12px; font: 400 23px/1.3 var(--font-body); color: var(--muted); text-align: center; }
.fx-lbls span b { display: block; font: 600 17px var(--font-mono); letter-spacing: .1em; text-transform: uppercase; color: var(--accent); margin-bottom: 4px; }
.eqrow { display: flex; align-items: center; gap: 28px; }
.eqnum { font: 500 22px var(--font-mono); color: var(--muted); }
.katex .ce { color: var(--e); } .katex .ch { color: var(--h); } .katex .cp { color: var(--ph); }
.katex .ca { color: var(--accent); } .katex .cg { color: var(--good); } .katex .cm { color: var(--muted); } .katex .cb { color: var(--bad); }
.katex .chh { color: var(--heat); }

/* ---------- Step animations ---------- */
.slide [data-step] {
  opacity: 0; transform: translateY(26px);
  --dl: calc(var(--d, 0ms) + var(--b, 0ms));
  transition: opacity .65s var(--ease-out) var(--dl), transform .8s var(--ease-out) var(--dl),
              filter .7s var(--ease-out) var(--dl), clip-path .9s var(--ease-io) var(--dl),
              stroke-dashoffset 1.2s var(--ease-io) var(--dl);
}
.slide.back [data-step] { transition-delay: 0ms !important; transition-duration: .35s !important; }
.slide svg [data-step] { transform-box: fill-box; transform-origin: center; }
.slide [data-step].fx-fade { transform: none; }
.slide [data-step].fx-left { transform: translateX(-46px); }
.slide [data-step].fx-right { transform: translateX(46px); }
.slide [data-step].fx-down { transform: translateY(-26px); }
.slide [data-step].fx-scale { transform: scale(.86); }
.slide [data-step].fx-pop { transform: scale(.3); transition-timing-function: var(--ease-out), var(--ease-back), ease, ease, ease; transition-duration: .4s, .6s, .5s, .5s, .5s; }
.slide [data-step].fx-blur { transform: none; filter: blur(14px); }
.slide [data-step].fx-wipe { transform: none; clip-path: inset(0 100% 0 0); }
.slide [data-step].fx-wipe-up { transform: none; clip-path: inset(100% 0 0 0); }
.slide [data-step].fx-grow-x { transform: scaleX(0); transform-origin: left center; }
.slide [data-step].fx-grow-y { transform: scaleY(0); transform-origin: center bottom; }
.slide [data-step].fx-grow-xr { transform: scaleX(0); transform-origin: right center; }
.slide [data-step].fx-draw { opacity: 1; transform: none; stroke-dasharray: 1 1; stroke-dashoffset: 1; }
.slide [data-step].fx-none { transform: none; transition: opacity .01s var(--d, 0ms); }
.slide [data-step].is-in { opacity: 1; transform: none; filter: none; clip-path: inset(-10% -10% -10% -10%); stroke-dashoffset: 0; }
.slide [data-step].fx-wipe.is-in, .slide [data-step].fx-wipe-up.is-in { clip-path: inset(-10% -10% -10% -10%); }
.slide [data-hide] { transition: opacity .5s var(--ease-out), transform .6s var(--ease-out); }
.slide [data-hide].is-gone.is-gone { opacity: 0; transform: translateY(-18px); pointer-events: none; }
.slide svg [data-hide].is-gone.is-gone { transform: none; }
.slide [data-dim] { transition: opacity .6s ease, filter .6s ease; }
.slide [data-dim].is-dim { opacity: .2; filter: saturate(.3); }

/* marker highlight */
.mk { background-image: linear-gradient(transparent 58%, color-mix(in oklab, var(--accent) 42%, transparent) 58%, color-mix(in oklab, var(--accent) 42%, transparent) 92%, transparent 92%);
  background-repeat: no-repeat; background-size: 0% 100%; transition: background-size .9s var(--ease-out); color: var(--text); padding: 0 .05em; }
.mk.is-marked { background-size: 100% 100%; }
.katex [data-mark] { border-radius: 10px; transition: background-color .5s ease, box-shadow .5s ease; }
.katex [data-mark].is-marked { background-color: color-mix(in oklab, var(--accent) 24%, transparent); box-shadow: 0 0 0 6px color-mix(in oklab, var(--accent) 24%, transparent); }
[data-strike] { position: relative; }
[data-strike]::after { content: ""; position: absolute; left: -6%; right: -6%; top: 52%; height: 4px; border-radius: 4px; background: var(--bad);
  transform: scaleX(0) rotate(-9deg); transform-origin: left center; transition: transform .6s var(--ease-out); }
[data-strike].is-struck::after { transform: scaleX(1) rotate(-9deg); }
[data-strike].is-struck { opacity: .55; transition: opacity .6s; }

/* ---------- SVG vocabulary ---------- */
.slide svg { overflow: visible; display: block; }
.slide svg text { font-family: var(--font-body); fill: var(--text-2); font-size: 24px; }
.slide svg .lb { font-size: 26px; font-weight: 500; fill: var(--text-2); }
.slide svg .lb-b { font-size: 30px; font-weight: 700; fill: var(--text); font-family: var(--font-display); }
.slide svg .lb-s { font-size: 21px; fill: var(--muted); }
.slide svg .lb-m { font-family: var(--font-mono); font-size: 19px; fill: var(--muted); letter-spacing: .06em; }
.slide svg .v { font-family: KaTeX_Math, 'Times New Roman', serif; font-style: italic; font-size: 30px; fill: var(--text); }
.slide svg .v .sub, .slide svg .sub { font-size: 21px; font-style: normal; font-family: KaTeX_Main, 'Times New Roman', serif; }
.slide svg .vm { font-family: KaTeX_Main, 'Times New Roman', serif; font-size: 28px; fill: var(--text); }
.slide svg .f-e { fill: var(--e); } .slide svg .f-h { fill: var(--h); } .slide svg .f-ph { fill: var(--ph); } .slide svg .f-ac { fill: var(--accent); }
.slide svg .f-tx { fill: var(--text); } .slide svg .f-mu { fill: var(--muted); } .slide svg .f-good { fill: var(--good); } .slide svg .f-heat { fill: var(--heat); }
.slide svg .f-bad { fill: var(--bad); }
.slide svg .ln { stroke: var(--text-2); stroke-width: 3; fill: none; stroke-linecap: round; }
.slide svg .ln-thin { stroke: var(--line-2); stroke-width: 2; fill: none; }
.slide svg .ln-e { stroke: var(--e); } .slide svg .ln-h { stroke: var(--h); } .slide svg .ln-ph { stroke: var(--ph); }
.slide svg .ln-ac { stroke: var(--accent); } .slide svg .ln-mu { stroke: var(--muted); } .slide svg .ln-good { stroke: var(--good); } .slide svg .ln-tx { stroke: var(--text); }
.slide svg .ln-heat { stroke: var(--heat); } .slide svg .ln-bad { stroke: var(--bad); }
.slide svg .dash { stroke-dasharray: 14 10; }
.slide svg .dot2 { stroke-dasharray: 3 9; stroke-linecap: round; }
.slide svg .w2 { stroke-width: 2; } .slide svg .w4 { stroke-width: 4; } .slide svg .w5 { stroke-width: 5; } .slide svg .w6 { stroke-width: 6; }
.slide svg .el { fill: var(--e); }
.slide svg .ho { fill: var(--bg); stroke: var(--h); stroke-width: 4; }
.slide svg .el.glow, .slide svg .ho.glow { filter: url(#glow); }
.slide svg .photon { fill: none; stroke: var(--ph); stroke-width: 3.5; stroke-linecap: round; stroke-linejoin: round; }
.slide svg .heat { fill: none; stroke: var(--heat); stroke-width: 3; stroke-linecap: round; stroke-linejoin: round; }
.slide svg .cb-fill { fill: url(#g-cb); } .slide svg .vb-fill { fill: url(#g-vb); }
.slide svg .panel { fill: var(--panel); stroke: var(--line); stroke-width: 1.5; }
.slide svg .axis { stroke: var(--muted); stroke-width: 2.5; fill: none; }
.slide svg .tick { stroke: var(--muted); stroke-width: 2; }
.slide svg .gridln { stroke: var(--line); stroke-width: 1.5; }
.slide svg .curve { fill: none; stroke-width: 5; stroke-linecap: round; stroke-linejoin: round; }
.slide svg .area { stroke: none; }
.slide svg .fx-draw { fill: none; }

/* continuous motion helpers */
@keyframes spin { to { transform: rotate(360deg); } }
@keyframes pulse { 0%, 100% { opacity: .55; } 50% { opacity: 1; } }
@keyframes floaty { 0%, 100% { transform: translateY(0); } 50% { transform: translateY(-8px); } }
@keyframes dashflow { to { stroke-dashoffset: -48; } }
@keyframes jiggle { 0%, 100% { transform: translate(0, 0); } 25% { transform: translate(3px, -2px); } 50% { transform: translate(-2px, 2px); } 75% { transform: translate(2px, 3px); } }
.slide.is-active .jiggle { animation: jiggle 1.6s ease-in-out infinite; animation-delay: var(--jd, 0s); }
.slide.is-active .pulse { animation: pulse 2.2s ease-in-out infinite; }
.slide.is-active .flow { stroke-dasharray: 16 16; animation: dashflow 1s linear infinite; }
.slide.is-active .flow.rev { animation-direction: reverse; }

/* ---------- Layout helpers ---------- */
.row { display: flex; gap: 40px; }
.col { display: flex; flex-direction: column; gap: 28px; }
.g2 { display: grid; grid-template-columns: 1fr 1fr; gap: 56px; }
.g3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 34px; }
.g4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: 26px; }
.split { display: grid; grid-template-columns: 1fr 1fr; gap: 64px; height: 100%; align-items: center; }
.split.l5 { grid-template-columns: 5fr 7fr; }
.split.l7 { grid-template-columns: 7fr 5fr; }
.split.l6 { grid-template-columns: 6fr 5fr; }
.center { display: grid; place-items: center; }
.abs { position: absolute; }
.stack > * + * { margin-top: 26px; }
.stack-sm > * + * { margin-top: 16px; }
.mt-s { margin-top: 18px; } .mt { margin-top: 32px; } .mt-l { margin-top: 52px; }
.fig { position: relative; }
.fig svg { width: 100%; height: auto; }
.fig-cap { margin-top: 14px; font: 400 22px/1.4 var(--font-body); color: var(--muted); text-align: center; }
.src { position: absolute; left: 120px; bottom: 36px; font: 400 18px/1.3 var(--font-mono); letter-spacing: .04em; color: var(--muted); }
.foot { font: 400 21px/1.4 var(--font-body); color: var(--muted); }
canvas.sim { display: block; border-radius: 24px; }
.simbox { position: relative; border-radius: 26px; border: 1px solid var(--line); background: color-mix(in oklab, var(--bg-2) 70%, transparent); overflow: hidden; }
.simbox .sb-lbl { position: absolute; font: 500 19px/1 var(--font-mono); letter-spacing: .1em; text-transform: uppercase; color: var(--muted); }
.legend { display: flex; flex-wrap: wrap; gap: 26px; font: 400 23px/1.2 var(--font-body); color: var(--text-2); }
.legend span { display: inline-flex; align-items: center; gap: 10px; }
.lg-e { width: 18px; height: 18px; border-radius: 50%; background: var(--e); }
.lg-h { width: 18px; height: 18px; border-radius: 50%; border: 4px solid var(--h); }
.lg-ph { width: 30px; height: 4px; background: var(--ph); border-radius: 2px; }
.lg-line { width: 30px; height: 0; border-top: 4px solid currentColor; }
.lg-dash { width: 30px; height: 0; border-top: 4px dashed currentColor; }

/* ---------- Title slide ---------- */
.s-title .t-kick { position: absolute; left: 120px; top: 120px; }
.s-title .t-main { position: absolute; left: 112px; top: 200px; width: 980px; }
.s-title h1 { margin: 0; font: 800 176px/.9 var(--font-display); letter-spacing: -.05em; color: var(--text); }
.s-title h1 .l2 { display: block; font-size: 112px; letter-spacing: -.04em; margin-top: 14px; color: var(--text-2); }
.s-title h1 .grad { background: linear-gradient(100deg, var(--e) 0%, var(--ph) 55%, var(--h) 100%); -webkit-background-clip: text; background-clip: text; color: transparent; }
.s-title .t-en { margin-top: 34px; font: 500 30px/1.3 var(--font-mono); letter-spacing: .02em; color: var(--muted); }
.s-title .t-en b { color: var(--text-2); font-weight: 600; }
.s-title .t-team { position: absolute; left: 120px; bottom: 112px; width: 940px; }
.s-title .t-team .tag { color: var(--ph); }
.team { display: grid; grid-template-columns: 1fr 1fr; gap: 16px 30px; margin-top: 20px; }
.member { display: flex; align-items: center; gap: 16px; font: 500 28px/1.2 var(--font-body); color: var(--text); }
.member .av { width: 50px; height: 50px; font-size: 22px; }
.member small { display: block; font: 400 19px/1.3 var(--font-mono); color: var(--muted); letter-spacing: .04em; margin-top: 4px; }
.s-title .t-win { position: absolute; right: 110px; top: 110px; width: 700px; height: 860px; }
.s-title .t-win .simbox { position: absolute; inset: 0; }
.bandlbl { position: absolute; font: 500 21px/1 var(--font-mono); letter-spacing: .08em; color: var(--muted); text-transform: uppercase; }
.bandlbl.v { font-family: KaTeX_Math, serif; text-transform: none; letter-spacing: 0; font-size: 30px; font-style: italic; color: var(--text-2); }
.bandlbl.v sub { font-family: KaTeX_Main, serif; font-style: normal; font-size: 20px; }

/* ---------- TOC ---------- */
.toc { display: flex; flex-direction: column; gap: 18px; }
.toc-row { display: grid; grid-template-columns: 120px 1fr 380px; align-items: center; gap: 30px; padding: 22px 34px 22px 28px; border-radius: 24px;
  background: var(--panel); border: 1px solid var(--line); position: relative; overflow: hidden; }
.toc-row::before { content: ""; position: absolute; left: 0; top: 0; bottom: 0; width: 6px; background: var(--c); }
.toc-row .num { font: 800 64px/1 var(--font-display); letter-spacing: -.04em; color: var(--c); }
.toc-row h3 { margin: 0; font: 700 34px/1.15 var(--font-display); color: var(--text); letter-spacing: -.01em; }
.toc-row p { margin: 8px 0 0; font: 400 23px/1.35 var(--font-body); color: var(--muted); }
.toc-row p .sec { font-family: var(--font-mono); color: var(--text-2); margin-right: 10px; }
.toc-who { display: flex; align-items: center; gap: 16px; justify-self: end; }
.toc-who .av { width: 54px; height: 54px; font-size: 24px; background: var(--c); }
.toc-who b { display: block; font: 600 28px/1.2 var(--font-body); color: var(--text); }
.toc-who small { font: 500 17px/1 var(--font-mono); letter-spacing: .12em; text-transform: uppercase; color: var(--muted); }
.toc-mini { display: flex; justify-content: space-between; font: 400 23px/1.3 var(--font-body); color: var(--muted); padding: 0 8px; }
.toc-mini b { color: var(--text-2); font-weight: 600; }

/* ---------- Opener (section transition) ---------- */
.opener { background: var(--op); color: var(--ink); overflow: hidden; }
.opener .op-motif { position: absolute; inset: 0; width: 100%; height: 100%; opacity: .9; }
.opener .op-motif * { vector-effect: non-scaling-stroke; }
.opener .op-num { position: absolute; right: -40px; bottom: -150px; font: 800 820px/.8 var(--font-display); letter-spacing: -.07em;
  color: transparent; -webkit-text-stroke: 3px rgba(11, 11, 16, .28); user-select: none; }
.opener .op-num.fill { color: rgba(11, 11, 16, .07); -webkit-text-stroke: 0; transform: translate(18px, 18px); }
.opener .op-done { position: absolute; left: 120px; top: 92px; display: inline-flex; align-items: center; gap: 14px; padding: 12px 22px 12px 14px; border-radius: 999px;
  background: rgba(11, 11, 16, .1); font: 600 22px/1 var(--font-body); color: var(--ink); }
.opener .op-done i { width: 34px; height: 34px; border-radius: 50%; display: grid; place-items: center; background: var(--ink); color: var(--op); font-style: normal; font-size: 20px; }
.opener .op-main { position: absolute; left: 120px; top: 228px; width: 1220px; }
.opener .op-label { font: 600 22px/1 var(--font-mono); letter-spacing: .18em; text-transform: uppercase; color: rgba(11, 11, 16, .7); }
.opener .op-title { margin: 26px 0 0; font: 800 124px/.95 var(--font-display); letter-spacing: -.04em; color: var(--ink); }
.opener .op-en { margin-top: 26px; font: 500 32px/1.2 var(--font-mono); color: rgba(11, 11, 16, .62); }
.opener .op-topics { list-style: none; padding: 0; margin: 50px 0 0; display: flex; flex-wrap: wrap; gap: 14px; max-width: 1180px; }
.opener .op-topics li { padding: 12px 22px; border-radius: 999px; border: 2px solid rgba(11, 11, 16, .78); font: 600 25px/1.2 var(--font-body); color: var(--ink); }
.opener .op-who { position: absolute; left: 120px; bottom: 150px; display: flex; align-items: center; gap: 24px; }
.opener .op-av { width: 104px; height: 104px; border-radius: 50%; display: grid; place-items: center; background: var(--ink); color: var(--op);
  font: 800 50px/1 var(--font-display); box-shadow: 0 0 0 10px rgba(11, 11, 16, .1); }
.opener .op-who small { display: block; font: 600 19px/1 var(--font-mono); letter-spacing: .18em; text-transform: uppercase; color: rgba(11, 11, 16, .62); }
.opener .op-who b { display: block; margin-top: 10px; font: 800 52px/1 var(--font-display); letter-spacing: -.02em; color: var(--ink); }
.opener .op-track { position: absolute; left: 120px; right: 120px; bottom: 64px; display: grid; grid-template-columns: repeat(4, 1fr); gap: 12px; }
.opener .op-track span { position: relative; padding-top: 18px; font: 600 18px/1.2 var(--font-mono); letter-spacing: .08em; text-transform: uppercase; color: rgba(11, 11, 16, .5); }
.opener .op-track span::before { content: ""; position: absolute; left: 0; right: 0; top: 0; height: 6px; border-radius: 3px; background: rgba(11, 11, 16, .16); }
.opener .op-track span.done { color: rgba(11, 11, 16, .75); }
.opener .op-track span.done::before { background: rgba(11, 11, 16, .55); }
.opener .op-track span.cur { color: var(--ink); }
.opener .op-track span.cur::before { background: var(--ink); }
.opener .op-hint { position: absolute; right: 120px; bottom: 150px; font: 600 20px/1 var(--font-mono); letter-spacing: .14em; text-transform: uppercase; color: rgba(11, 11, 16, .55); }

/* ---------- Quiz ---------- */
.quiz-q { font: 600 46px/1.32 var(--font-body); color: var(--text); max-width: 1600px; }
.quiz-q .m-inl { white-space: nowrap; }
.opts { display: grid; grid-template-columns: repeat(var(--cols, 3), 1fr); gap: 28px; margin-top: 54px; }
.opt { position: relative; display: flex; align-items: center; gap: 22px; padding: 30px 32px; border-radius: 24px; border: 2px solid var(--line-2); background: var(--panel);
  font: 500 34px/1.3 var(--font-body); color: var(--text); transition: border-color .5s, background .5s, opacity .5s, transform .5s var(--ease-back); }
.opt .ol { flex: none; width: 60px; height: 60px; border-radius: 16px; display: grid; place-items: center; font: 700 28px/1 var(--font-display); background: var(--panel-2); color: var(--text-2); transition: background .5s, color .5s; }
.opt small { display: block; font-size: 23px; color: var(--muted); margin-top: 4px; }
.opt.is-right.is-marked { border-color: var(--good); background: color-mix(in oklab, var(--good) 14%, transparent); transform: scale(1.03); }
.opt.is-right.is-marked .ol { background: var(--good); color: var(--ink); }
.opt.is-right::after { content: "✓"; position: absolute; right: 26px; top: 50%; transform: translateY(-50%) scale(0); width: 50px; height: 50px; border-radius: 50%; display: grid; place-items: center;
  background: var(--good); color: var(--ink); font: 800 28px/1 var(--font-body); transition: transform .5s var(--ease-back) .2s; }
.opt.is-right.is-marked::after { transform: translateY(-50%) scale(1); }
.quiz-badge { position: absolute; right: 120px; top: 96px; width: 150px; height: 150px; border-radius: 50%; display: grid; place-items: center;
  background: var(--accent); color: var(--ink); font: 800 96px/1 var(--font-display); transform: rotate(8deg); box-shadow: 0 0 0 14px color-mix(in oklab, var(--accent) 16%, transparent); }
.slide.is-active .quiz-badge { animation: floaty 3s ease-in-out infinite; }

/* ---------- Recap ---------- */
.recap { display: grid; grid-template-columns: repeat(var(--cols, 3), 1fr); gap: 28px; }
.recap .card { padding: 34px 34px 38px; }
.recap .card .rn { font: 800 54px/1 var(--font-display); color: var(--accent); letter-spacing: -.03em; }
.recap .card p { margin-top: 18px; font-size: 28px; color: var(--text-2); }
.recap .card .M { margin-top: 18px; }
.nextbar { position: absolute; left: 0; right: 0; bottom: 0; display: flex; align-items: center; gap: 22px; padding: 24px 30px; border-radius: 22px;
  background: var(--panel); border: 1px solid var(--line); font: 500 28px/1.2 var(--font-body); color: var(--text-2); }
.nextbar .tag { color: var(--muted); }
.nextbar .av { width: 50px; height: 50px; font-size: 22px; background: var(--nc); }
.nextbar b { color: var(--text); }
.nextbar .go { margin-left: auto; font: 600 20px var(--font-mono); letter-spacing: .12em; color: var(--nc); text-transform: uppercase; }

/* ---------- Example / data chips ---------- */
.given { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 16px; }
.given .gv { padding: 18px 22px; border-radius: 18px; background: var(--panel); border: 1px solid var(--line); }
.given .gv small { display: block; font: 500 17px/1.2 var(--font-mono); letter-spacing: .1em; text-transform: uppercase; color: var(--muted); margin-bottom: 8px; }
.given .gv .M { font-size: 30px; }
.solve { display: flex; flex-direction: column; gap: 22px; }
.solve .sv { display: grid; grid-template-columns: 64px 1fr; gap: 18px; align-items: start; }
.solve .sv .sn { width: 52px; height: 52px; border-radius: 50%; display: grid; place-items: center; background: var(--accent); color: var(--ink); font: 800 24px/1 var(--font-display); }
.solve .sv .sh { font: 600 27px/1.3 var(--font-body); color: var(--text); }
.solve .sv .M { font-size: 32px; margin-top: 6px; }

/* energy bar for Example 4-1 */
.ebar { position: relative; height: 96px; border-radius: 20px; overflow: hidden; display: flex; border: 1px solid var(--line-2); }
.ebar > div { display: grid; place-items: center; font: 700 28px/1.1 var(--font-body); color: var(--ink); text-align: center; }
.ebar .eb1 { background: var(--e); flex: 1.43; }
.ebar .eb2 { background: var(--heat); flex: .57; }
.ebar small { display: block; font: 600 18px/1.2 var(--font-body); }

/* ---------- Thank-you ---------- */
.s-end .end-main { position: absolute; left: 120px; top: 170px; width: 1100px; }
.s-end h1 { margin: 0; font: 800 150px/.92 var(--font-display); letter-spacing: -.05em; color: var(--text); }
.s-end h1 .grad { background: linear-gradient(100deg, var(--e), var(--ph) 55%, var(--h)); -webkit-background-clip: text; background-clip: text; color: transparent; }
.s-end .qa { margin-top: 40px; display: inline-flex; align-items: center; gap: 18px; padding: 16px 30px; border-radius: 999px; border: 2px solid var(--line-2);
  font: 700 38px/1 var(--font-display); color: var(--text); }
.s-end .qa i { width: 18px; height: 18px; border-radius: 50%; background: var(--good); box-shadow: 0 0 0 7px color-mix(in oklab, var(--good) 25%, transparent); }
.s-end .refs { position: absolute; left: 120px; bottom: 96px; width: 1080px; font: 400 22px/1.5 var(--font-body); color: var(--muted); }
.s-end .refs b { color: var(--text-2); font-weight: 600; }

/* ---------- Overlays ---------- */
#nav { position: fixed; right: 22px; bottom: 22px; z-index: 50; display: flex; gap: 8px; opacity: 0; transform: translateY(8px); transition: opacity .35s, transform .35s; }
body.show-ui #nav { opacity: 1; transform: none; }
#nav button { width: 46px; height: 46px; border-radius: 14px; border: 1px solid var(--line-2); background: color-mix(in oklab, var(--bg-2) 85%, transparent);
  -webkit-backdrop-filter: blur(10px); backdrop-filter: blur(10px); display: grid; place-items: center; cursor: pointer; color: var(--text-2); }
#nav button:hover { color: var(--text); border-color: var(--text-2); }
#nav svg { width: 22px; height: 22px; fill: none; stroke: currentColor; stroke-width: 2; stroke-linecap: round; stroke-linejoin: round; }
#hint { position: fixed; left: 50%; bottom: 26px; transform: translateX(-50%); z-index: 50; padding: 12px 22px; border-radius: 999px; background: color-mix(in oklab, var(--bg-2) 85%, transparent);
  border: 1px solid var(--line); font: 400 14px/1.4 var(--font-body); color: var(--muted); white-space: nowrap; transition: opacity .6s, transform .6s; -webkit-backdrop-filter: blur(10px); backdrop-filter: blur(10px); }
#hint.gone { opacity: 0; transform: translate(-50%, 10px); pointer-events: none; }
#hint kbd { font-size: 12px; }
.overlay { position: fixed; inset: 0; z-index: 80; display: grid; place-items: center; padding: 4vh 4vw; background: rgba(4, 5, 9, .62);
  -webkit-backdrop-filter: blur(8px); backdrop-filter: blur(8px); opacity: 0; pointer-events: none; transition: opacity .3s; }
.overlay.on { opacity: 1; pointer-events: auto; }
.ov-card { width: min(720px, 100%); max-height: 92vh; overflow: auto; border-radius: 22px; background: var(--bg-2); border: 1px solid var(--line-2); padding: 26px 30px 30px; box-shadow: var(--shadow); }
.ov-card.ov-wide { width: min(1280px, 100%); }
.ov-head { display: flex; align-items: center; justify-content: space-between; margin-bottom: 14px; }
.ov-head h3 { margin: 0; font: 700 24px/1.2 var(--font-display); }
.ov-x { width: 38px; height: 38px; border-radius: 12px; border: 1px solid var(--line-2); background: transparent; cursor: pointer; }
.keys { display: grid; grid-template-columns: auto 1fr; gap: 12px 22px; margin: 0; font-size: 15px; }
.keys dt { white-space: nowrap; } .keys dd { margin: 0; color: var(--text-2); }
.menu-cols { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 18px; }
.menu-part h4 { margin: 0 0 8px; display: flex; align-items: center; gap: 10px; font: 600 12px/1.2 var(--font-mono); letter-spacing: .12em; text-transform: uppercase; color: var(--c); }
.menu-part h4 i { width: 9px; height: 9px; border-radius: 50%; background: var(--c); }
.menu-part h4 small { color: var(--muted); letter-spacing: 0; text-transform: none; font-family: var(--font-body); }
.menu-part ol { list-style: none; margin: 0; padding: 0; }
.menu-part li button { width: 100%; text-align: left; display: flex; gap: 10px; padding: 7px 10px; border-radius: 9px; border: 0; background: transparent; cursor: pointer;
  font: 400 14px/1.3 var(--font-body); color: var(--text-2); }
.menu-part li button span { font: 500 12px/1.6 var(--font-mono); color: var(--muted); min-width: 22px; }
.menu-part li button:hover { background: var(--panel-2); color: var(--text); }
.menu-part li button.cur { background: color-mix(in oklab, var(--c) 18%, transparent); color: var(--text); }
#notes-pane { position: fixed; left: 50%; bottom: 18px; transform: translate(-50%, 140%); width: min(1100px, 92vw); max-height: 34vh; overflow: auto; z-index: 60; border-radius: 18px;
  background: color-mix(in oklab, var(--bg-2) 94%, transparent); border: 1px solid var(--line-2); padding: 16px 22px; transition: transform .45s var(--ease-out); box-shadow: var(--shadow);
  -webkit-backdrop-filter: blur(10px); backdrop-filter: blur(10px); }
#notes-pane.on { transform: translate(-50%, 0); }
.np-head { display: flex; justify-content: space-between; font: 600 12px/1 var(--font-mono); letter-spacing: .12em; text-transform: uppercase; color: var(--accent); margin-bottom: 10px; }
.np-body { font: 400 18px/1.55 var(--font-body); color: var(--text); }
.np-body p { margin: 0 0 8px; }
#blackout { position: fixed; inset: 0; background: #000; z-index: 95; opacity: 0; pointer-events: none; transition: opacity .4s; }
#blackout.on { opacity: 1; pointer-events: auto; }
#laser { position: fixed; left: 0; top: 0; width: 26px; height: 26px; margin: -13px 0 0 -13px; border-radius: 50%; pointer-events: none; z-index: 90; display: none;
  background: radial-gradient(circle, #fff 0 16%, #ff2a4f 28%, rgba(255, 42, 79, .4) 52%, transparent 72%); }
body.laser, body.laser * { cursor: none !important; }
body.laser #laser { display: block; }
#jump { position: fixed; left: 50%; top: 50%; transform: translate(-50%, -50%); z-index: 70; padding: 18px 34px; border-radius: 20px; background: var(--bg-2); border: 1px solid var(--line-2);
  font: 700 54px/1 var(--font-mono); color: var(--text); opacity: 0; pointer-events: none; transition: opacity .2s; }
#jump.on { opacity: 1; }
#loader { position: fixed; inset: 0; z-index: 200; display: grid; place-content: center; justify-items: center; gap: 22px; background: var(--bg); font: 400 15px var(--font-body); color: var(--muted); transition: opacity .6s; }
#loader.gone { opacity: 0; pointer-events: none; }
.ld-bands { width: 120px; height: 60px; position: relative; }
.ld-bands i { position: absolute; left: 0; right: 0; height: 6px; border-radius: 3px; }
.ld-bands i:first-child { top: 6px; background: var(--e); animation: pulse 1.2s infinite; }
.ld-bands i:last-child { bottom: 6px; background: var(--h); animation: pulse 1.2s .6s infinite; }

/* ---------- Presenter mode ---------- */
#presenter { display: none; }
body.presenter { background: #05060a; }
body.presenter #viewport { left: 18px; top: 86px; right: auto; bottom: auto; width: calc(64vw - 27px); height: calc((64vw - 27px) * 9 / 16); border-radius: 14px; border: 1px solid var(--line-2); }
body.presenter #presenter { display: block; }
body.presenter #nav, body.presenter #hint { display: none; }
.pv-top { position: fixed; left: 18px; right: 18px; top: 14px; height: 58px; display: flex; align-items: center; justify-content: space-between; }
.pv-part { display: flex; align-items: center; gap: 14px; }
.pv-part .av { width: 46px; height: 46px; font-size: 20px; background: var(--accent); }
.pv-part small { display: block; font: 600 12px/1 var(--font-mono); letter-spacing: .14em; text-transform: uppercase; color: var(--accent); }
.pv-part b { display: block; margin-top: 6px; font: 700 21px/1 var(--font-display); color: var(--text); }
.pv-clock { display: flex; align-items: center; gap: 14px; font: 700 34px/1 var(--font-mono); color: var(--text); }
.pv-clock small { font: 500 15px var(--font-mono); color: var(--muted); }
.pv-clock button { width: 36px; height: 36px; border-radius: 10px; border: 1px solid var(--line-2); background: transparent; cursor: pointer; color: var(--text-2); font-size: 18px; }
.pv-side { position: fixed; top: 86px; right: 18px; bottom: 18px; width: calc(36vw - 27px); display: flex; flex-direction: column; gap: 12px; }
.pv-meta { display: flex; justify-content: space-between; font: 500 14px var(--font-mono); color: var(--muted); }
.pv-meta b { color: var(--text); }
.pv-notes { flex: 1; overflow: auto; padding: 18px 20px; border-radius: 14px; background: var(--bg-2); border: 1px solid var(--line); font: 400 clamp(16px, 1.45vw, 24px)/1.55 var(--font-body); color: var(--text); }
.pv-notes p { margin: 0 0 12px; }
.pv-notes b { color: var(--accent); }
.pv-next { padding: 14px 18px; border-radius: 14px; background: var(--panel); border: 1px solid var(--line); }
.pv-next small { display: block; font: 600 11px/1 var(--font-mono); letter-spacing: .14em; text-transform: uppercase; color: var(--muted); margin-bottom: 6px; }
.pv-next b { font: 600 17px/1.3 var(--font-body); color: var(--text-2); }
.pv-btns { display: grid; grid-template-columns: 1fr 2fr; gap: 10px; }
.pv-btns button { height: 54px; border-radius: 12px; border: 1px solid var(--line-2); background: var(--panel-2); cursor: pointer; font: 600 17px var(--font-body); color: var(--text); }
.pv-btns #pv-go { background: var(--accent); color: var(--ink); border: 0; }

/* ---------- Embedded / small screens ---------- */
@media (max-aspect-ratio: 1/1) {
  #hint { white-space: normal; width: 90vw; text-align: center; }
}
@media (prefers-reduced-motion: reduce) {
  .slide [data-step] { transition-duration: .01s !important; }
}

/* ---------- Roadmap ---------- */
.rm { display: flex; flex-direction: column; align-items: center; text-align: center; }
.rm-ico { width: 230px; height: 230px; border-radius: 50%; display: grid; place-items: center; background: var(--bg-2); position: relative; z-index: 1;
  border: 2px solid color-mix(in oklab, var(--c) 65%, transparent); box-shadow: 0 0 0 12px color-mix(in oklab, var(--c) 10%, transparent), 0 30px 60px -30px color-mix(in oklab, var(--c) 60%, transparent); }
.rm-ico svg { width: 160px; height: 160px; }
.rm-n { margin-top: 34px; font: 600 18px/1 var(--font-mono); letter-spacing: .16em; text-transform: uppercase; color: var(--c); }
.rm h3 { margin: 14px 0 20px; font: 700 34px/1.15 var(--font-display); color: var(--text); letter-spacing: -.01em; }
.rm .M { font-size: 30px; color: var(--text-2); }

/* =========================================================
   Diagram & scene styles
   ========================================================= */
.katex .text, .katex .text * { font-family: var(--font-body) !important; }
.slide.is-active .flow { stroke-dasharray: 16 8; }
.slide svg .halo { fill: none; stroke: var(--accent); stroke-width: 2.5; stroke-dasharray: 4 6; }
.slide.is-active svg .halo { animation: spin 9s linear infinite; transform-box: fill-box; transform-origin: center; }

/* opener motifs */
@keyframes opwave { to { transform: translateX(-120px); } }
.slide.is-active .op-motif .mv { animation: opwave 3s linear infinite; }
@keyframes opring { 0% { transform: scale(.25); opacity: 0; } 20% { opacity: 1; } 100% { transform: scale(1.7); opacity: 0; } }
.op-motif .ring { transform-box: fill-box; transform-origin: center; opacity: 0; }
.slide.is-active .op-motif .ring { animation: opring 4.2s ease-out infinite; animation-delay: var(--rd, 0s); }
@keyframes opup { 0%, 100% { transform: translateY(0); } 50% { transform: translateY(-46px); } }
@keyframes opdn { 0%, 100% { transform: translateY(0); } 50% { transform: translateY(46px); } }
.slide.is-active .op-motif .up { animation: opup 6s ease-in-out infinite; }
.slide.is-active .op-motif .dn { animation: opdn 6s ease-in-out infinite; }
@keyframes opstream { to { stroke-dashoffset: -140; } }
.op-motif .stream { stroke-dasharray: 60 40 20 20; }
.slide.is-active .op-motif .stream { animation: opstream 2.6s linear infinite; }
.opener .op-topics { max-width: 1000px; }

/* absorption cards */
.absorb { display: flex; flex-direction: column; }
.absorb svg { width: 100%; height: auto; margin-top: 8px; }
.ab-h { display: flex; align-items: center; justify-content: space-between; }
.ab-h .m { font-size: 34px; }
.ab-tag { font: 600 16px/1 var(--font-mono); letter-spacing: .12em; text-transform: uppercase; padding: 9px 14px; border-radius: 999px; }
.ab-tag.good { color: var(--good); background: color-mix(in oklab, var(--good) 15%, transparent); }
.ab-tag.bad { color: var(--bad); background: color-mix(in oklab, var(--bad) 15%, transparent); }
.ab-cap { margin: 6px 0 0; font: 400 25px/1.4 var(--font-body); color: var(--text-2); text-align: center; }

/* Fig 4-1 motions */
.slide svg .hmove { transition: transform 1.5s var(--ease-io) .3s; }
.slide svg .hmove.is-marked { transform: translateX(280px); }
.slide svg .vanish { transition: opacity .3s ease .7s !important; }
.slide svg .edrop { transition: transform .6s cubic-bezier(.55,0,.9,.45), opacity .25s ease .55s; }
.slide svg .edrop.is-marked { transform: translateY(246px); opacity: 0; }

/* luminescence */
.lum { display: flex; flex-direction: column; }
.lum .lum-ico { width: 100%; height: auto; margin-bottom: 18px; }
.lum h3 { margin: 10px 0 10px; }

/* fluorescence vs phosphorescence */
.glowbox { position: relative; height: 660px; border-radius: 28px; border: 1px solid var(--line); background: radial-gradient(120% 80% at 50% 0%, var(--panel-2), transparent 70%); padding: 34px 36px; }
.lamp { display: flex; align-items: center; gap: 20px; }
.lamp svg { width: 160px; height: 96px; }
.lamp-bulb { fill: var(--ph); transition: fill .3s; }
.lamp-rays line { stroke: var(--ph); stroke-width: 6; stroke-linecap: round; transition: opacity .25s; }
.lamp.is-marked .lamp-bulb { fill: var(--line-2); }
.lamp.is-marked .lamp-rays line { opacity: 0; }
.lamp-l b { font: 600 22px/1.2 var(--font-mono); letter-spacing: .08em; text-transform: uppercase; }
.lamp-l .on-t { color: var(--ph); }
.lamp-l .off-t { display: none; color: var(--muted); }
.lamp.is-marked .on-t { display: none; }
.lamp.is-marked .off-t { display: inline; }
.orbs { display: grid; grid-template-columns: 1fr 1fr; gap: 30px; margin-top: 70px; }
.orb-w { display: flex; flex-direction: column; align-items: center; text-align: center; }
.orb-w b { margin-top: 44px; font: 700 34px/1.1 var(--font-display); color: var(--text); }
.orb-w small { margin-top: 8px; font: 400 21px var(--font-mono); color: var(--muted); }
.orb { width: 210px; height: 210px; border-radius: 50%; }
.orb.fl { background: radial-gradient(circle at 42% 38%, #fff 0 6%, var(--e) 40%, color-mix(in oklab, var(--e) 35%, transparent) 70%, transparent 72%);
  box-shadow: 0 0 90px 24px color-mix(in oklab, var(--e) 55%, transparent); transition: opacity .25s ease, box-shadow .25s ease; }
.orb.ph { background: radial-gradient(circle at 42% 38%, #fff 0 6%, var(--ph) 40%, color-mix(in oklab, var(--ph) 35%, transparent) 70%, transparent 72%);
  box-shadow: 0 0 90px 24px color-mix(in oklab, var(--ph) 55%, transparent); transition: opacity 9s cubic-bezier(.1,.55,.3,1), box-shadow 9s cubic-bezier(.1,.55,.3,1); }
.orb.is-marked { opacity: .08; box-shadow: 0 0 0 0 transparent; }

/* spectrum labels */
.slide svg .mat .mat-bg { fill: var(--bg); stroke: transparent; stroke-width: 2.5; transition: fill .5s, stroke .5s; }
.slide svg .mat.is-marked .mat-bg { fill: color-mix(in oklab, var(--accent) 24%, var(--bg)); stroke: var(--accent); }

/* indirect recombination & trap */
.slide svg .rc-a { transition: transform .7s cubic-bezier(.55,0,.9,.45) .2s, opacity .3s ease .85s; }
.slide svg .rc-a.is-marked { transform: translateY(162px); opacity: 0; }
.slide svg .rc-hole { transition: opacity .3s ease .85s; }
.slide svg .rc-hole.is-marked { opacity: 0; }
.slide svg .rc-b { transition: transform .7s cubic-bezier(.55,0,.9,.45) .2s; }
.slide svg .rc-b.is-marked { transform: translateY(162px); }
.slide svg .tr-e { transition: transform .9s var(--ease-io) .9s; }
.slide svg .tr-e.is-marked { transform: translateY(92px); transition: transform .6s cubic-bezier(.55,0,.9,.45) .15s; }

/* decay */
.decay-wrap { position: relative; }
.slide svg .decay-ghost { fill: none; stroke: var(--line-2); stroke-width: 3; stroke-dasharray: 6 8; }
.decay-box { width: 290px; height: 230px; display: grid; grid-template-columns: repeat(10, 1fr); gap: 7px; padding: 16px; border-radius: 16px; border: 1px solid var(--line-2); background: var(--bg-2); align-content: start; box-sizing: border-box; }
.decay-box i { width: 18px; height: 18px; border-radius: 50%; background: var(--e); box-shadow: 0 0 10px color-mix(in oklab, var(--e) 60%, transparent); transition: opacity .35s, transform .35s; }
.decay-box i.gone { opacity: 0; transform: scale(2.2); }
.decay-read { position: absolute; right: 26px; top: 300px; display: flex; flex-direction: column; gap: 8px; font: 500 25px var(--font-mono); color: var(--muted); text-align: right; }
.decay-read b { color: var(--text); }

/* quasi-Fermi motions */
.slide svg .qf { transition: transform 1.3s var(--ease-io) .25s; }
.slide svg .qf-n.is-marked { transform: translateY(-6px); }
.slide svg .qf-p.is-marked { transform: translateY(210px); }
.slide svg .qf-up.is-marked { transform: translateY(-239px); }
@keyframes efq { 0%, 100% { transform: translateY(0); } 25% { transform: translateY(-14px); } 75% { transform: translateY(14px); } }
.slide.is-active svg .efq { animation: efq 1.4s ease-in-out infinite; }

/* tub */
.tub-svg .tub-pipe { fill: none; stroke: var(--muted); stroke-width: 22; stroke-linecap: round; stroke-linejoin: round; }
.tub-svg .tub-pipe.thin { stroke-width: 18; }
.tub-svg .tub-nozzle { fill: var(--muted); }
.tub-svg .tub-wall { fill: none; stroke: var(--text-2); stroke-width: 6; stroke-linejoin: round; }
.tub-svg .tub-water { fill: color-mix(in oklab, var(--e) 30%, transparent); }
.tub-svg .tub-surf { fill: none; stroke: var(--e); stroke-width: 4; }
.tub-svg .tub-in { stroke: var(--ph); stroke-linecap: butt; stroke-dasharray: 28 20; opacity: .9; }
.tub-svg .tub-out { stroke: var(--h); stroke-linecap: butt; stroke-dasharray: 28 20; }
.slide.is-active .tub-svg .tub-in, .slide.is-active .tub-svg .tub-out { animation: dashflow .5s linear infinite; }

/* photoconductor */
.pc-svg .pc-bulb { fill: var(--line-2); transition: fill .4s; }
.pc-svg.on .pc-bulb { fill: var(--ph); filter: url(#glow); }
.pc-svg .pc-rays line { stroke: var(--ph); stroke-width: 4; stroke-linecap: round; stroke-dasharray: 12 12; opacity: 0; transition: opacity .4s; }
.pc-svg.on .pc-rays line { opacity: .85; animation: dashflow 1s linear infinite; }
.pc-svg .pc-wire { fill: none; stroke: var(--text-2); stroke-width: 4; stroke-linejoin: round; }
.pc-svg .pc-bat { stroke: var(--text-2); stroke-width: 4; }
.pc-svg .pc-bat.thick { stroke-width: 9; }
.pc-svg .pc-bar { fill: var(--panel-2); stroke: var(--line-2); stroke-width: 2; transition: fill .6s; }
.pc-svg.on .pc-bar { fill: color-mix(in oklab, var(--ph) 14%, var(--bg)); }
.pc-svg .pc-contact { fill: var(--muted); }
.pc-svg .pc-meter { fill: var(--bg-2); stroke: var(--text-2); stroke-width: 4; }
.pc-svg .pc-scale { fill: none; stroke: var(--muted); stroke-width: 3; stroke-dasharray: 3 9; }
.pc-svg .pc-needle { stroke: var(--bad); stroke-width: 5; stroke-linecap: round; }
.pc-svg .pc-carriers circle { transition: opacity .6s; }

/* tangent */
.tg-svg .tg-line { stroke: var(--accent); stroke-width: 4; stroke-linecap: round; }
.tg-svg .tg-drop { stroke: var(--muted); stroke-width: 2; stroke-dasharray: 6 6; }
.tg-svg .tg-dot { fill: var(--accent); }
.tg-svg .tg-flux { stroke: var(--text); stroke-width: 6; stroke-linecap: round; }

/* directions table */
.dirs { display: flex; flex-direction: column; gap: 16px; }
.dir { display: grid; grid-template-columns: 200px 1fr; gap: 24px; align-items: center; font: 400 28px/1.3 var(--font-body); color: var(--text-2); padding: 12px 22px; border-radius: 16px; background: var(--panel); border: 1px solid var(--line); }
.dir svg { width: 200px; height: 30px; }
.mech { padding: 24px 26px 30px; }
.mech p { font-size: 27px; }

/* built-in field */
.bi-svg .bi-ion circle { fill: var(--bg); stroke: var(--text-2); stroke-width: 2.5; transition: stroke .6s, fill .6s; }
.bi-svg .bi-ion text { font: 700 22px var(--font-body); fill: var(--text-2); transition: fill .6s; }
.bi-svg .bi-ions.is-marked .bi-ion.lft circle { stroke: var(--accent); fill: color-mix(in oklab, var(--accent) 25%, var(--bg)); }
.bi-svg .bi-ions.is-marked .bi-ion.lft text { fill: var(--accent); }
.bi-svg .bi-e { transition: transform 1.8s var(--ease-io); }
.bi-svg .bi-es.is-marked .bi-e { transform: translateX(var(--dx)); }
.bi-svg .bi-bal.is-marked .bi-es.is-marked .bi-e { transform: translateX(var(--dx2)); }

/* tilted bands */
.slide svg .tilt { transform-box: fill-box; transform-origin: 50% 50%; transition: transform 1.4s var(--ease-io) .2s; }
.slide svg .tilt.is-marked { transform: rotate(-6deg); }
.slide svg .tilt-l { transition: transform 1.4s var(--ease-io) .2s; }
.slide svg .tilt-l.is-marked { transform: translateY(-38px); }
.slide svg .roll-e, .slide svg .roll-h { transition: transform 2.2s cubic-bezier(.45,0,.55,1) .5s; }
.slide svg .roll-e.is-marked { transform: translate(-500px, 52px); }
.slide svg .roll-h.is-marked { transform: translate(500px, -54px); }

/* Einstein */
.einst { position: relative; display: flex; flex-direction: column; gap: 26px; padding-left: 74px; }
.einst .eqnum { min-width: 50px; }
.einst-arrow { position: absolute; left: 0; top: 30px; width: 60px; height: 400px; overflow: visible; }

/* table */
.tbl { width: 100%; border-collapse: separate; border-spacing: 0; font: 500 30px/1.2 var(--font-body); color: var(--text); }
.tbl th { font: 600 24px/1.2 var(--font-body); color: var(--text-2); padding: 14px 18px; text-align: right; border-bottom: 2px solid var(--line-2); }
.tbl th small { display: block; font: 400 16px var(--font-mono); color: var(--muted); margin-top: 4px; }
.tbl td { padding: 16px 18px; text-align: right; border-bottom: 1px solid var(--line); font-variant-numeric: tabular-nums; }
.tbl td:first-child, .tbl th:first-child { text-align: left; font-weight: 700; font-family: var(--font-display); }
.tbl tr.hl td { background: color-mix(in oklab, var(--accent) 12%, transparent); }

/* continuity */
.slide svg .badge-c { fill: var(--bg); stroke: var(--text-2); stroke-width: 2.5; }
@keyframes fd { 0% { transform: translateX(110px); opacity: 0; } 15% { opacity: 1; } 85% { opacity: 1; } 100% { transform: translateX(360px); opacity: 0; } }
@keyframes fd2 { 0% { transform: translateX(640px); opacity: 0; } 15% { opacity: 1; } 85% { opacity: 1; } 100% { transform: translateX(890px); opacity: 0; } }
.slide svg .fd { fill: var(--bg); stroke: var(--h); stroke-width: 3.5; opacity: 0; }
.slide.is-active svg .fd { animation: fd 1.8s linear infinite; animation-delay: var(--fd, 0s); }
.slide.is-active svg .out .fd { animation-name: fd2; }
.cbox { padding: 28px 32px; border-radius: 22px; background: var(--panel); border: 1px solid var(--line-2); }
.ceq { display: flex; flex-wrap: wrap; align-items: center; gap: 12px 16px; margin-top: 18px; font: 700 32px/1.2 var(--font-display); }
.ceq > span { color: var(--muted); font-weight: 500; }

/* chain */
.chain { display: flex; flex-wrap: wrap; align-items: center; gap: 12px; }
.chain > span { padding: 12px 18px; border-radius: 14px; background: var(--panel-2); border: 1px solid var(--line-2); font: 600 24px/1.2 var(--font-body); color: var(--text); }
.chain > i { font-style: normal; color: var(--accent); font: 700 26px var(--font-body); }
.chain.big > span { font-size: 28px; padding: 14px 22px; }

/* summary flow & cheat sheet */
.flow6 { position: relative; display: grid; grid-template-columns: repeat(3, 1fr); grid-template-rows: 260px 260px; gap: 40px 56px; }
.fn { position: relative; z-index: 1; padding: 26px 30px; border-radius: 24px; background: var(--bg-2); border: 1px solid color-mix(in oklab, var(--c) 55%, transparent);
  box-shadow: 0 0 0 6px color-mix(in oklab, var(--c) 8%, transparent); }
.fn .fn-n { position: absolute; right: 24px; top: 18px; font: 800 46px/1 var(--font-display); color: color-mix(in oklab, var(--c) 75%, transparent); }
.fn h4 { margin: 0 0 16px; font: 700 31px/1.15 var(--font-display); color: var(--text); max-width: 82%; }
.fn .M { font-size: 25px; color: var(--text-2); }
.fn small { display: block; margin-top: 14px; font: 600 16px var(--font-mono); letter-spacing: .12em; text-transform: uppercase; color: var(--c); }
.flow6-arrows { position: absolute; inset: 0; width: 100%; height: 100%; z-index: 0; overflow: visible; }
.cheat { display: grid; grid-template-columns: repeat(4, 1fr); gap: 24px; }
.cs { padding: 24px 26px 26px; border-radius: 22px; background: var(--panel); border: 1px solid var(--line); border-top: 6px solid var(--c); min-height: 300px; display: flex; flex-direction: column; gap: 16px; }
.cs small { font: 600 17px var(--font-mono); letter-spacing: .12em; text-transform: uppercase; color: var(--c); }
.cs .M.sm { font-size: 31px; }
.cs .M.xs { font-size: 25px; color: var(--text-2); }

/* Haynes–Shockley */
.hs-svg .hs-ghosts path { fill: none; stroke: var(--h); stroke-width: 2.5; stroke-dasharray: 6 8; opacity: .55; }

/* ---------- review fixes ---------- */
.title .en { vertical-align: baseline; font-size: 28px; }
.rm h3 { font-size: 30px; white-space: nowrap; }
.solve { gap: 40px; }
.opt.is-dim { opacity: .35; }
.recap .card { min-height: 330px; }
.recap .card p { font-size: 29px; }
.recap .card .M.xs { font-size: 28px; }
.recap[style*="--cols:4"] .card p { font-size: 27px; }
.given.one { grid-template-columns: 1fr; }
.given .gv .M { font-size: 30px; }
.opener .op-title { font-size: 116px; }
.cs .M.sm { font-size: 34px; }
.cs .M.xs { font-size: 27px; }
.cs { gap: 20px; }
#chrome:not(.off) .topbar, #chrome:not(.off) .stepdots { transition-delay: .6s; }