/* Site redesign round 3, step B4: the reading pages (notes, unit and chapter pages, the course books) in
   the R10 system. Markup from scripts/lib/r3-reading.mjs; boards docs/redesign-r3/r10/boards/R10-Notes,
   R10-Notes-Phone, R10-Unit, R10-Learn. Loaded after assets/course/r3.css, which supplies the band, the
   type and the course colour (data-cover).
   Layout: the short cover band, then the shell as cards overlapping it: contents rail | reading card |
   side column (notes pages). Colours come from theme tokens and the course variables, so dark mode follows. */

/* ---- the band over a reading page ---- */
.r3-read-top{padding-bottom:0;background-image:none}
.r3-read-top .band.short .hwrap{padding-bottom:86px;grid-template-columns:1.55fr 1fr;align-items:center}
.r3-read-top .band .art{max-width:280px}
.r3-read-top .band [class*="crumb"]{margin:0 0 12px;font:800 13px var(--font-ui);color:rgba(255,255,255,.82)}
.r3-read-top .band [class*="crumb"] a{color:#fff;text-decoration:none}
.r3-read-top .band [class*="crumb"] a:hover{text-decoration:underline}
.r3-read-top .band [class*="crumb"] [aria-current]{color:#fff;font-weight:900}
.r3-read-top .band .issue{margin:0 0 10px}
.r3-read-top .band .issue .bio-beta,.r3-read-top .band .issue [class*="beta"]{text-transform:none;letter-spacing:0}
.r3-read-top .band h1.deck{font:900 clamp(40px,4.6vw,56px)/1 var(--display);letter-spacing:-.04em;margin:4px 0 8px;color:#fff;max-width:none;padding:0}
.r3-read-top .band h1.deck span{display:block;color:var(--bac)}
.r3-read-top .band .hand{margin:0 0 18px;font-size:clamp(19px,2vw,23px)}
.r3-read-top .band .hero-ctas{margin:0 0 16px}
.r3-read-top .band .hero-ctas a,.r3-read-top .band .hero-ctas button{font-size:15.5px;padding:12px 18px;border:0;cursor:pointer}
.r3-read-top .band .hero-ctas > *{display:inline-flex;align-items:center;gap:8px;line-height:1.2}
.r3-read-top .band .hero-ctas i{font-style:normal;display:inline;width:auto;height:auto;background:none;border:0;margin:0;font-size:12px;line-height:1}
.r3-read-top .band .btn-chan{background:#FFD23F;color:#0B1A33}
.r3-read-top .band .btn-ghost{background:transparent;color:#fff;box-shadow:inset 0 0 0 1.5px rgba(255,255,255,.45)}
.r3-read-top .band .btn-ghost:hover{box-shadow:inset 0 0 0 1.5px #fff}
.r3-read-top .band .r3-chips{display:flex;flex-wrap:wrap;gap:8px;margin:0 0 12px;padding:0;font:800 12.5px var(--font-ui);color:#fff}
.r3-read-top .band .r3-chips > span,.r3-read-top .band .r3-chips .bk-small,.r3-read-top .band .r3-chips .bk-chip{display:inline-block;background:rgba(255,255,255,.14);color:#fff;border-radius:999px;padding:4px 11px;font:800 12.5px var(--font-ui);border:0;margin:0}
.r3-read-top .band .r3-links{display:flex;flex-wrap:wrap;gap:6px 16px;margin:0;font:800 13.5px var(--font-ui)}
.r3-read-top .band .r3-links a,.r3-read-top .band .r3-links button{background:none;border:0;padding:0;color:#fff;font:inherit;cursor:pointer;text-decoration:none;box-shadow:none;min-height:0}
.r3-read-top .band .r3-links a:hover,.r3-read-top .band .r3-links button:hover{text-decoration:underline}
.r3-read-top .band .r3-links .sr-only{position:absolute}
.r3-read-top .band .r3-links > *{margin:0 !important;padding:0 !important}
.r3-read-top .band .r3-links .bk-action::before{display:none}

/* ---- the shell as cards over the band ---- */
.tb-shell.r3-read{display:grid;grid-template-columns:230px minmax(0,1fr);gap:24px;align-items:start;max-width:1180px;margin:-56px auto 0;padding:0 24px 40px;position:relative;z-index:2;background-image:none}
.tb-shell.r3-read.bk-notes,.tb-shell.r3-read.bk-book:has(.r3-side){grid-template-columns:230px minmax(0,1fr) 260px}
.tb-shell.r3-read > .tb-rail{background:var(--white);border-radius:20px;box-shadow:0 0 0 1px var(--line),0 18px 40px -26px rgba(11,26,51,.35);padding:18px 14px 20px;top:calc(var(--site-header-h,112px) + 16px)}
.tb-shell.r3-read > .tb-rail .tb-rail-title{color:var(--accent);padding:0 6px}
.tb-shell.r3-read .bk-toc-chap{border-radius:12px}
.tb-shell.r3-read > .tb-main{background:var(--white);border-radius:22px;box-shadow:0 0 0 1px var(--line),0 22px 50px -30px rgba(11,26,51,.4);padding:30px clamp(22px,3.2vw,40px) 36px;max-width:none;min-width:0}
.tb-shell.r3-read.bk-chapter > .tb-main{padding-top:24px}
/* The reading card is the one card: the prose inside it loses the old inner box and its narrow cap. */
.tb-shell.r3-read .tb-main > .bk-prose,.tb-shell.r3-read .tb-main > article{border:0;box-shadow:none;background:none;padding:0;border-radius:0;max-width:none;margin-left:0;margin-right:0}
.tb-shell.r3-read > .tb-main > .bk-lede{margin:0 0 20px;font:500 17px/1.7 var(--font-body,var(--font-ui));color:var(--ink);max-width:none}
.tb-shell.r3-read h2{font:900 clamp(22px,2.3vw,27px)/1.18 var(--display);letter-spacing:-.025em;margin:0 0 10px}
.tb-shell.r3-read h2 span{display:inline;color:inherit}
.tb-shell.r3-read .bk-sec-head{display:flex;flex-wrap:wrap;align-items:baseline;gap:4px 12px;margin:0 0 14px}
.tb-shell.r3-read .bk-sec-head h2{margin:0;flex:1 1 300px;display:flex;align-items:baseline;gap:12px}
.tb-shell.r3-read .bk-sec-head .bk-toc-n{background:none;color:var(--accent);font:900 26px/1 var(--display);letter-spacing:-.04em;padding:0;min-width:0;height:auto;border-radius:0}
.tb-shell.r3-read .bk-sec{border:0;border-top:2px solid var(--ink);border-radius:0;box-shadow:none;background:none;padding:20px 0 0;margin:28px 0 0}
.tb-shell.r3-read .bk-sec .domain-tag{background:none;padding:0;color:var(--muted);font:700 12.5px var(--font-ui);flex-basis:100%}
.tb-shell.r3-read .bk-h{color:var(--ink)}
.tb-shell.r3-read .bk-h::after{content:"";display:inline-block}
/* the course book (R10-Learn): the band names the book, so its contents heading and intro are kept for
   screen readers and the outline only */
.tb-shell.r3-read .tb-static-toc > h1,.tb-shell.r3-read .tb-static-toc > h1 + p{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}
.r3-learn .band .lede{color:rgba(255,255,255,.82);margin:0 0 18px}
.tb-shell.r3-read .tb-static-toc h2,.tb-shell.r3-read .tb-static-toc h3{font:900 18px/1.25 var(--display);letter-spacing:-.015em;margin:22px 0 8px;color:var(--ink)}
.tb-shell.r3-read .tb-static-toc ol{margin:0;padding:0;list-style:none;display:grid;grid-template-columns:repeat(auto-fill,minmax(260px,1fr));gap:0 22px}
.tb-shell.r3-read .tb-static-toc li{border-bottom:1px solid var(--line);padding:9px 0}
.tb-shell.r3-read .tb-static-toc li a{font:800 15px/1.35 var(--font-ui);color:var(--ink);text-decoration:none}
.tb-shell.r3-read .tb-static-toc li a b{display:inline-block;min-width:34px;font:900 20px/1 var(--display);color:var(--accent);letter-spacing:-.04em}
.tb-shell.r3-read .tb-static-toc li a:hover{color:var(--accent)}

/* unit and chapter pages (R10-Unit) */
.tb-shell.r3-read h2#h-topics span{color:var(--accent)}
.tb-shell.r3-read.bk-chapter h2.bk-h:not(#h-topics){display:flex;align-items:center;gap:12px;font:900 12.5px var(--font-ui);letter-spacing:.12em;text-transform:uppercase;color:var(--accent);margin:30px 0 12px}
.tb-shell.r3-read.bk-chapter h2.bk-h:not(#h-topics)::after{content:"";flex:1;height:2px;background:var(--ink);display:block}
.tb-shell.r3-read .bk-list{border:0;box-shadow:none;background:none;padding:0;border-radius:0}
.tb-shell.r3-read .bk-row{border-radius:0;border:0;border-bottom:1px solid var(--line);background:none;padding:12px 0}
.tb-shell.r3-read .bk-row:last-child{border-bottom:0}
.tb-shell.r3-read .bk-row-n{background:none;color:var(--accent);font:900 22px/1 var(--display);letter-spacing:-.04em;min-width:52px;padding:0;height:auto;border-radius:0;text-align:left}
.tb-shell.r3-read .bk-row-title{font:900 16px/1.3 var(--display);letter-spacing:-.01em;color:var(--ink)}
.tb-shell.r3-read .bk-row-btns .bk-btn{background:var(--ctint);color:var(--accent);border:0;box-shadow:none;font:900 13.5px var(--font-ui);padding:7px 13px;border-radius:9px}
.tb-shell.r3-read .bk-row-btns .bk-btn:hover{filter:brightness(.96)}
.tb-shell.r3-read .tb-chapter-nav{margin-top:26px}
.tb-shell.r3-read .tb-chapter-link{background:var(--white);border:1px solid var(--line);border-radius:16px}

/* ---- the side column on notes pages ---- */
.r3-side{position:sticky;top:calc(var(--site-header-h,112px) + 16px);display:flex;flex-direction:column;gap:14px;min-width:0}
.r3-side-card{background:var(--white);border-radius:18px;box-shadow:0 0 0 1px var(--line);padding:16px 16px 18px;font:600 14px/1.5 var(--font-ui);color:var(--muted)}
.r3-side-card p{margin:0 0 10px}
.r3-side-card .k{font:900 11.5px var(--font-ui);letter-spacing:.1em;text-transform:uppercase;color:var(--accent);margin:0 0 6px}
.r3-side-go{display:inline-block;font:900 14.5px var(--font-ui);color:var(--accent);text-decoration:none}
.r3-side-go:hover{text-decoration:underline}
.r3-side-card.navy{background:#0B1A33;box-shadow:none;color:rgba(255,255,255,.8)}
.r3-side-card.navy .k{color:var(--bac)}
.r3-side-card.navy .r3-side-go{color:#fff;font-size:16px}
.r3-side-card .h{font:900 17px/1.25 var(--display);color:#fff;margin:0 0 6px}
.r3-side-tools .chapter-tools{display:flex;flex-direction:column;align-items:stretch;text-align:left;gap:10px;margin:0;padding:0;background:none;border:0;box-shadow:none}
.r3-side-tools .chapter-tools__k{font:900 11.5px var(--font-ui);letter-spacing:.1em;text-transform:uppercase;color:var(--accent);text-align:left}
.r3-side-tools .chapter-tools a{display:block;font:900 14.5px var(--font-ui);color:var(--ink);text-decoration:none;padding:9px 0 0;margin:0;border:0;border-top:1px solid var(--line);border-radius:0;background:none;box-shadow:none;text-align:left}
.r3-side-tools .chapter-tools a small{display:block;font:600 12.5px var(--font-ui);color:var(--muted)}
:root[data-theme="dark"] .r3-side-card.navy{background:#16294A}

/* ---- glossary and course search (R10-Glossary, R10-Search) ---- */
.r3.r3-page{background-image:none;padding-bottom:32px}
.r3.r3-page > [class*="crumb"]{display:none}
.r3-pagetop .band .lede{color:rgba(255,255,255,.82);margin:0;max-width:40em}
.r3-glossary .gx{margin-top:-60px;position:relative;z-index:2}
.r3-glossary .gx-tools,.r3-glossary .gx-status,.r3-glossary .gx-rail{background:var(--white);margin:0;box-shadow:0 0 0 1px var(--line)}
.r3-glossary .gx-tools{border-radius:22px 22px 0 0;padding:22px 24px 10px;display:grid;grid-template-columns:minmax(0,1fr) 240px;gap:16px;align-items:end}
.r3-glossary .gx-tools::before{content:"Find a term";grid-column:1/-1;font:900 12px var(--font-ui);letter-spacing:.1em;text-transform:uppercase;color:var(--accent);margin:0 0 -8px}
.r3-glossary .gx-tools > *{min-width:0}
.r3-glossary .gx-ch,.r3-glossary .gx-ch select{width:100%;max-width:100%;box-sizing:border-box}
.r3-glossary .gx-status{padding:0 24px;min-height:0;clip-path:inset(0 -1px)}
.r3-glossary .gx-rail{border-radius:0 0 22px 22px;padding:8px 24px 20px;display:flex;flex-wrap:wrap;gap:6px;position:static;clip-path:inset(0 -1px -1px -1px)}
.r3-glossary .gx-rail a,.r3-glossary .gx-rail span{display:inline-grid;place-items:center;min-width:30px;height:30px;border-radius:8px;background:var(--ctint);color:var(--accent);font:900 13px var(--font-ui);text-decoration:none}
.r3-glossary .gx-rail a:hover{background:var(--accent);color:var(--white)}
.r3-glossary .gx-rail .gx-off{background:none;color:var(--muted);opacity:.5}
.r3-glossary .gx-group{margin:34px 0 0;border-top:2px solid var(--ink);padding-top:14px}
.r3-glossary .gx-group h2{font:900 40px/1 var(--display);letter-spacing:-.04em;color:var(--accent);display:flex;align-items:baseline;gap:10px;margin:0 0 14px}
.r3-glossary .gx-group h2 .gx-n{font:700 13px var(--font-ui);letter-spacing:0;color:var(--muted)}
.r3-glossary .gx-terms{display:grid;grid-template-columns:minmax(0,1fr);gap:0;background:none;border:0;box-shadow:none;padding:0;margin:0}
/* One term per row, like a dictionary (Olivier, 2026-10-26): the term on the left, its definition beside it. */
.r3-glossary .gx-t{display:grid;grid-template-columns:minmax(180px,280px) minmax(0,1fr);gap:4px 28px;padding:14px 0;border:0;border-top:1px solid var(--line);background:none;min-width:0}
.r3-glossary .gx-t > dd{max-width:72ch}
.r3-glossary .gx-t dt{font:900 16px/1.3 var(--display);color:var(--ink)}
.r3-glossary .gx-t dd{margin:0;font:500 14px/1.5 var(--font-ui);color:var(--muted)}
.r3-glossary .gx-src{display:block;margin-top:6px;font:800 13px var(--font-ui);color:var(--accent)}
.r3-glossary .gx-src a{color:var(--accent)}
.r3-search #app,.r3-search .bio-app-mount{position:relative;z-index:2;margin-top:-60px;background:var(--white);border-radius:22px;box-shadow:0 0 0 1px var(--line),0 22px 50px -30px rgba(11,26,51,.4);padding:24px clamp(18px,3vw,30px) 28px}
@media (max-width:900px){
  .r3-glossary .gx-tools{grid-template-columns:1fr}
  .r3-glossary .gx-terms{grid-template-columns:minmax(0,1fr)}
  .r3-glossary .gx-t{grid-template-columns:minmax(0,1fr)}
  .r3-glossary .gx,.r3-search #app,.r3-search .bio-app-mount{margin-top:-44px}
}

/* ---- lessons (R10-Lesson): the hero is the band, the steps are the card over it ---- */
.r3.r3-lesson{background-image:none;padding-bottom:28px}
.r3-lesson > .hero,.r3-lesson > [class$="-ls-hero"]{position:relative;background-color:var(--bbg);color:#fff;box-shadow:0 0 0 100vmax var(--bbg);clip-path:inset(0 -100vmax);border:0;border-radius:0;margin:0 0 0;padding:30px min(34%,330px) 96px 0;background-repeat:no-repeat;background-position:right 0 center;background-size:min(30%,300px) auto}
.r3-lesson[data-cover="nremt"] > .hero,.r3-lesson[data-cover="nremt"] > [class$="-ls-hero"]{background-image:url(../covers/art/nremt.svg)}
.r3-lesson[data-cover="ochem"] > .hero,.r3-lesson[data-cover="ochem"] > [class$="-ls-hero"]{background-image:url(../covers/art/ochem.svg)}
.r3-lesson[data-cover="anp"] > .hero,.r3-lesson[data-cover="anp"] > [class$="-ls-hero"]{background-image:url(../covers/art/anp.svg)}
.r3-lesson[data-cover="apbio"] > [class$="-ls-hero"]{background-image:url(../covers/art/apbio.svg)}
.r3-lesson[data-cover="apchem"] > [class$="-ls-hero"]{background-image:url(../covers/art/apchem.svg)}
.r3-lesson[data-cover="apphys"] > [class$="-ls-hero"]{background-image:url(../covers/art/apphys.svg)}
.r3-lesson[data-cover="apcalc"] > [class$="-ls-hero"]{background-image:url(../covers/art/apcalc.svg)}
.r3-lesson[data-cover="apstat"] > [class$="-ls-hero"]{background-image:url(../covers/art/apstat.svg)}
.r3-lesson[data-cover="apenv"] > [class$="-ls-hero"]{background-image:url(../covers/art/apenv.svg)}
.r3-lesson[data-cover="appsych"] > [class$="-ls-hero"]{background-image:url(../covers/art/appsych.svg)}
.r3-lesson > .hero .eyebrow,.r3-lesson > [class$="-ls-hero"] .eyebrow{border:0;padding:0;color:rgba(255,255,255,.76);font:800 13px var(--font-ui);letter-spacing:.1em;text-transform:uppercase;background:none}
.r3-lesson > .hero h1,.r3-lesson > [class$="-ls-hero"] h1{color:#fff;font:900 clamp(40px,4.6vw,56px)/1 var(--display) !important;letter-spacing:-.04em;margin:10px 0 10px !important}
.r3-lesson > .hero .lede,.r3-lesson > [class$="-ls-hero"] .lede{color:rgba(255,255,255,.84) !important;font-size:17px;max-width:36em}
.r3-lesson > [class$="-ls-hero"] [class$="-tags"] span{background:rgba(255,255,255,.14);color:#fff;border:0}
.r3-lesson > .hero .lpv,.r3-lesson > [class$="-ls-hero"] .lpv{background:var(--white);color:var(--ink);border-radius:16px;max-width:560px}
.r3-lesson > .hero + *,.r3-lesson > [class$="-ls-hero"] + *{position:relative;z-index:2;margin-top:-56px}
.r3-lesson > [class$="-ls-card"],.r3-lesson > [class$="-ls-card"] + [class$="-ls-card"]{background:var(--white);border-radius:22px;box-shadow:0 0 0 1px var(--line),0 22px 50px -30px rgba(11,26,51,.4)}
:root[data-theme="dark"] .r3-lesson > .hero .lpv{background:var(--white)}
/* ochem lessons with the steps rail: the band spans both columns, the rail is a card over it */
.r3-lesson.lesson-shell:has(.lesson-rail) > .hero{grid-column:1 / -1;grid-row:1;padding-bottom:96px}
.r3-lesson.lesson-shell > .lesson-rail{grid-row:2 / span 30;margin-top:-56px;z-index:3;background:var(--white);border-radius:20px;box-shadow:0 0 0 1px var(--line),0 18px 40px -26px rgba(11,26,51,.35);padding:18px 14px 20px}
.r3-lesson.lesson-shell > .lesson-rail .lesson-rail-k{color:var(--accent)}
.r3-lesson .lesson-card{border-radius:22px;box-shadow:0 0 0 1px var(--line),0 22px 50px -30px rgba(11,26,51,.4)}
@media (max-width:900px){
  .r3-lesson > .hero,.r3-lesson > [class$="-ls-hero"]{padding:150px 0 76px;background-position:left 0 top 24px;background-size:150px auto}
  .r3-lesson > .hero + *,.r3-lesson > [class$="-ls-hero"] + *{margin-top:-44px}
}

/* ---- narrower screens ---- */
@media (max-width:1080px){
  .tb-shell.r3-read.bk-notes,.tb-shell.r3-read.bk-book:has(.r3-side){grid-template-columns:230px minmax(0,1fr)}
  .tb-shell.r3-read .r3-side{grid-column:2;position:static;display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr))}
}
@media (max-width:900px){
  .r3-read-top .band.short .hwrap{grid-template-columns:1fr;padding-bottom:70px}
  .r3-read-top .band .art{max-width:200px;order:-1;justify-self:start}
  .tb-shell.r3-read,.tb-shell.r3-read.bk-notes,.tb-shell.r3-read.bk-book:has(.r3-side){display:block;margin-top:-44px;padding:0 14px 32px}
  .tb-shell.r3-read > .tb-toc-btn{background:var(--white);margin:0 0 12px;position:relative;z-index:3}
  .tb-shell.r3-read > .tb-rail{margin:0 0 12px}
  .tb-shell.r3-read > .tb-main{padding:22px 18px 26px;border-radius:18px}
  .tb-shell.r3-read .r3-side{display:flex;margin-top:14px}
}
@media (max-width:560px){
  .r3-read-top .band.short .hwrap{padding-left:16px;padding-right:16px}
  .r3-read-top .band h1.deck{font-size:38px}
  .r3-read-top .band .art{max-width:150px}
}
@media print{
  .r3-read-top .band{background:none !important;color:#000}
  .r3-read-top .band::after,.r3-read-top .band .art,.r3-read-top .band .hero-ctas,.r3-read-top .band .r3-links,.r3-read-top .band .hand,.r3-side{display:none !important}
  .r3-read-top .band h1.deck,.r3-read-top .band h1.deck span{color:#000}
  .tb-shell.r3-read{margin-top:0}
  .tb-shell.r3-read > .tb-main{box-shadow:none;padding:0}
}

/* Round 3 notes column is narrower (the side rail sits beside it), so a 700-unit figure shrinks to the column
   instead of scrolling sideways, as lesson cards already do (theme.css); a sideways scroller also fails axe's
   keyboard rule. */
.r3-read .notes-figure svg{min-width:min(calc(var(--vb,420) * 0.92px), 100%);}

/* Phone reader: the Contents button stays pinned under the header while you read, so jumping to another lesson
   never means scrolling back to the top (Olivier, 2026-10-26). It already opens the full contents sheet. */
@media (max-width:860px){
  .tb-shell > .tb-toc-btn{position:sticky;top:calc(env(safe-area-inset-top,0px) + 78px);z-index:20;box-shadow:0 10px 24px -14px rgba(11,26,51,.45)}
  .tb-shell.r3-read > .tb-toc-btn{position:sticky}
}
@media (max-width:860px){
  /* Opened from anywhere in the chapter, the contents appear over the page where you are, not at the top. */
  body.tb-toc-open .tb-shell .tb-rail{position:fixed;left:12px;right:12px;top:calc(env(safe-area-inset-top,0px) + 128px);
    bottom:calc(env(safe-area-inset-bottom,0px) + 78px);z-index:19;overflow:auto;overscroll-behavior:contain;
    background:var(--white);border:1px solid var(--line);border-radius:18px;padding:14px;box-shadow:0 24px 60px -24px rgba(11,26,51,.55)}
  body.tb-toc-open .tb-shell .tb-rail .tb-contents{max-height:none}
}

/* Read | Interactive (assets/course/read-toggle.js): one switch at the top of the textbook and of each
   interactive lesson, in place of the per-section Lesson button (Olivier, 2026-10-26). On the textbook it
   stays in view while reading, so the section being read is one tap from its lesson. On a phone it sits on
   the same line as the sticky Contents button, to the right of it. */
.rt-bar{display:flex;justify-content:flex-end;align-items:flex-start;margin:0 0 18px;pointer-events:none}
.rt-bar.rt-book{position:sticky;top:calc(var(--site-header-h,112px) + 10px);z-index:6;height:0;margin:0;overflow:visible}
.rt-bar.rt-book + *{margin-top:0}
.rt-pill{pointer-events:auto;flex:none;display:inline-flex;align-items:center;gap:4px;max-width:100%;background:var(--white);border:1px solid var(--line);border-radius:999px;padding:4px;box-shadow:0 10px 24px -16px rgba(11,26,51,.45)}
.rt-cap{font:700 12.5px var(--font-ui);color:var(--muted);padding:0 8px 0 10px;max-width:22em;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.rt-cap:empty{display:none}
.rt-opt{display:inline-flex;align-items:center;gap:6px;min-height:36px;padding:0 14px;border-radius:999px;font:900 13.5px var(--font-ui);color:var(--ink);text-decoration:none;white-space:nowrap}
a.rt-opt:hover{background:var(--ctint,#EEF2F8);color:var(--ink)}
a.rt-opt:focus-visible{outline:3px solid var(--accent,var(--cink,#0B1A33));outline-offset:2px}
.rt-opt.on{background:var(--accent,var(--cink,#0B1A33));color:var(--paper,#fff)}
.rt-opt.off{color:var(--muted);opacity:.6;cursor:not-allowed}
.rt-tag{font:800 10.5px var(--font-ui);letter-spacing:.04em;text-transform:uppercase;padding:2px 6px;border-radius:6px;background:#FFD23F;color:#0B1A33}
/* the book's first block makes room under the floating switch */
.tb-main > .rt-book + *{padding-top:52px}
/* in the hero band, above the eyebrow */
.rt-bar.rt-inhero{justify-content:flex-start;margin:0 0 18px}
.r3-lesson > .rt-lesson{justify-content:flex-start;margin:0 0 16px}
html.rt-leaving .tb-main{visibility:hidden}
@media (max-width:860px){
  .rt-bar.rt-book{top:calc(env(safe-area-inset-top,0px) + 78px);z-index:21}
  .rt-cap{display:none}
  .rt-bar.rt-inhero{margin:0 0 14px}
  .rt-opt{min-height:34px;padding:0 12px;font-size:13px}
  .tb-main > .rt-book + *{padding-top:0}
  /* ochem's "In this chapter" menu sticks below the Contents row instead of under it (it used to sit at the
     header, behind the pinned Contents button) */
  .tb-shell:has(> .tb-toc-btn) .tb-jump{top:calc(env(safe-area-inset-top,0px) + 128px);z-index:19}
  .rt-bar.rt-book{margin-top:-52px;margin-bottom:52px}
}
/* a section opened from the contents or a link lands below the floating switch, not under it */
.tb-main:has(> .rt-book) .bk-sec{scroll-margin-top:calc(var(--site-header-h,112px) + 64px)}
@media (max-width:860px){.tb-main:has(> .rt-book) .bk-sec{scroll-margin-top:calc(env(safe-area-inset-top,0px) + 130px)}
  .tb-main:has(.tb-jump) .bk-sec{scroll-margin-top:calc(env(safe-area-inset-top,0px) + 186px)}}

/* AP® and A&P lessons on a wide screen: the hero band bleeds the full width, so the steps rail beside it is a
   card above the band (as ochem's lesson rail already is), instead of dark text hidden under the band. */
@media (min-width:901px){
  .cx-ls > aside{position:sticky;z-index:3;align-self:start;background:var(--white);border-radius:20px;box-shadow:0 0 0 1px var(--line),0 18px 40px -26px rgba(11,26,51,.35);padding:18px 14px 20px}
}