/* LearnML paper reader */
:root { --hl-y: #FFE58F; --hl-g: #BDEFCB; --hl-b: #CDE0FF; --hl-p: #FFD1E2; --sheet: #FFFFFF; }
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) { --hl-y: rgba(255, 214, 64, .30); --hl-g: rgba(88, 214, 141, .28); --hl-b: rgba(110, 160, 255, .30); --hl-p: rgba(255, 120, 170, .28); --sheet: #141C24; }
}
:root[data-theme="dark"] { --hl-y: rgba(255, 214, 64, .30); --hl-g: rgba(88, 214, 141, .28); --hl-b: rgba(110, 160, 255, .30); --hl-p: rgba(255, 120, 170, .28); --sheet: #141C24; }

.reader { position: fixed; inset: 0; z-index: 70; background: var(--bg); display: flex; flex-direction: column; padding-top: env(safe-area-inset-top, 0px); --rfs: 19px; }
.rbar { position: relative; display: flex; align-items: center; gap: 10px; padding: 8px 14px; border-bottom: 1px solid var(--line); background: var(--bg); }
.rbtn { display: inline-flex; align-items: center; gap: 6px; border: 1.5px solid var(--line); background: var(--surface); color: var(--ink); border-radius: 10px; padding: 7px 10px; font-weight: 700; font-size: .88rem; cursor: pointer; flex: none; }
.rbtn:hover { border-color: var(--muted); }
.rbtn svg { width: 18px; height: 18px; }
.rt-side svg { color: var(--cd); }
.rtitle { flex: 1; min-width: 0; display: flex; flex-direction: column; line-height: 1.25; }
.rtitle b { font: 700 .98rem var(--f-display); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.rsrc { font: 600 .7rem var(--f-mono); color: var(--muted); letter-spacing: .02em; }
.rtools { display: flex; gap: 6px; align-items: center; }
.rsize { display: flex; border: 1.5px solid var(--line); border-radius: 10px; overflow: hidden; }
.rsize button { border: 0; background: var(--surface); color: var(--ink); padding: 7px 10px; font-weight: 700; cursor: pointer; }
.rsize button + button { border-left: 1.5px solid var(--line); }
.rprog { position: absolute; left: 0; right: 0; bottom: -1px; height: 3px; }
.rprog i { display: block; height: 100%; width: 0; background: var(--hi); transition: width .15s linear; }

.rwrap { flex: 1; min-height: 0; display: grid; grid-template-columns: 250px minmax(0, 1fr) 410px; }
.reader:not(.side-open) .rwrap { grid-template-columns: 250px minmax(0, 1fr); }
.reader:not(.side-open) .rside { display: none; }
.rtoc { overflow-y: auto; border-right: 1px solid var(--line); padding: 18px 10px 40px; font-size: .86rem; background: var(--bg); }
.rtoc-h { font: 700 .7rem var(--f-mono); letter-spacing: .12em; text-transform: uppercase; color: var(--muted); margin: 0 8px 8px; }
.rtoc ol { list-style: none; margin: 0; padding: 0; }
.rtoc button { display: block; width: 100%; text-align: left; border: 0; background: none; padding: 5px 8px; border-radius: 8px; color: var(--muted); cursor: pointer; line-height: 1.3; font-size: inherit; }
.rtoc li.l3 button { padding-left: 20px; font-size: .82rem; }
.rtoc button:hover { color: var(--ink); }
.rtoc button.on { color: var(--ink); background: var(--surface); box-shadow: inset 3px 0 0 var(--hi); font-weight: 700; }
/* .rmain is a <main>: undo the app's page-level main{} rule (auto margins, max-width, padding) */
.rmain { overflow-y: auto; outline: none; margin: 0; max-width: none; padding: 0; min-width: 0; }
.rstage { max-width: 800px; margin: 0 auto; padding: 28px 20px 140px; }

/* the paper sheet */
.paper { background: var(--sheet); border: 1.5px solid var(--line); border-radius: 14px; padding: clamp(22px, 5vw, 60px); font: 400 var(--rfs)/1.72 "Literata", Georgia, "Times New Roman", serif; color: var(--ink); box-shadow: var(--shadow); overflow-wrap: break-word; }
.paper .ptitle { margin-bottom: 1.6em; }
.paper h1 { font: 800 clamp(1.6rem, 3.4vw, 2.35rem)/1.15 var(--f-display); letter-spacing: -.02em; margin: 0 0 .5em; text-wrap: balance; }
.paper .authors { font: 400 .78em/1.55 var(--f-body); color: var(--muted); margin: 0; }
.paper h2 { font: 800 1.32em/1.2 var(--f-display); letter-spacing: -.01em; margin: 2.1em 0 .6em; text-wrap: balance; scroll-margin-top: 18px; }
.paper h3 { font: 700 1.1em/1.25 var(--f-display); margin: 1.7em 0 .5em; scroll-margin-top: 18px; }
.paper h4, .paper h5 { font: 700 1em/1.3 var(--f-display); margin: 1.4em 0 .4em; scroll-margin-top: 18px; }
.paper .abs { background: color-mix(in srgb, var(--hi) 12%, transparent); border-radius: 12px; padding: 4px 20px 6px; margin: 0 0 1.4em; }
.paper .abs h2 { margin-top: .8em; font-size: 1.05em; }
.paper .kw { font: .8em/1.5 var(--f-body); color: var(--muted); }
.paper p { margin: 0 0 1em; }
.paper .ptag { font-family: var(--f-mono); font-size: .78em; color: var(--muted); margin-right: .35em; }
.paper .sc { font-variant: small-caps; }
.paper .runin { margin-right: .4em; }
.paper em { font-style: italic; }
.paper code { font-family: var(--f-mono); font-size: .82em; }
.paper pre { font: .78em/1.5 var(--f-mono); background: var(--surface2); padding: 12px; border-radius: 10px; overflow-x: auto; }
.paper blockquote, .paper .thm { margin: 1em 0; padding: .2em 1em; border-left: 3px solid var(--line); }
.paper ul.items, .paper ol.items { padding-left: 0; margin: 0 0 1em; }
.paper ul.items > li, .paper ol.items > li { list-style: none; position: relative; padding-left: 1.4em; margin: .35em 0; }
.paper li > .ptag:first-child { position: absolute; left: 0; top: .15em; margin: 0; }
.paper li > p { margin: 0 0 .4em; }
.paper figure { margin: 2em 0; text-align: center; position: relative; }
.paper figure img { max-width: 100%; height: auto; border-radius: 6px; background: #fff; cursor: zoom-in; }
.paper .subfigs { display: flex; flex-wrap: wrap; gap: 14px; justify-content: center; align-items: flex-end; }
.paper .subfig { flex: 1 1 200px; max-width: 100%; }
.paper figcaption { font: .8em/1.55 var(--f-body); color: var(--muted); text-align: left; margin-top: .7em; }
.paper figcaption .ptag { color: var(--ink); font-weight: 700; }
.tscroll { overflow-x: auto; margin: .6em 0; }
table.data { border-collapse: collapse; font: .74em/1.4 var(--f-body); margin: 0 auto; }
table.data td, table.data th { border-bottom: 1px solid var(--line); padding: 4px 8px; text-align: left; vertical-align: top; }
table.data th { font-weight: 700; }
.peq { position: relative; overflow-x: auto; margin: 1.1em 0; padding: .3em 0; }
.eqt { margin: 0 auto; border-collapse: collapse; }
.eqt td { padding: 0 .12em; }
.eqt td.eqno { text-align: right; color: var(--muted); font: .78em var(--f-mono); padding-left: 1.2em; white-space: nowrap; }
.eqt td.pad { width: 0; padding: 0; }
.paper math { font-size: 1.04em; }
.paper .pmb { display: block; overflow-x: auto; text-align: center; margin: 1em 0; position: relative; }
.paper cite { font-style: normal; }
.paper a.cref { font: .78em var(--f-mono); color: var(--ca); text-decoration: none; background: color-mix(in srgb, var(--ca) 10%, transparent); border-radius: 4px; padding: 0 .2em; }
.paper a.cref:hover { background: color-mix(in srgb, var(--ca) 22%, transparent); }
.paper a.xref { color: var(--ca); text-decoration: none; border-bottom: 1px solid color-mix(in srgb, var(--ca) 40%, transparent); }
.paper a.ext { color: var(--ca); }
.paper .fn { border: 0; background: none; color: var(--ca); font: 700 .72em var(--f-mono); cursor: pointer; padding: 0 .12em; }
.paper .gl { border-bottom: 2px dotted color-mix(in srgb, var(--cc) 75%, transparent); cursor: help; }
.paper .gl:hover, .paper .gl:focus-visible { background: color-mix(in srgb, var(--cc) 12%, transparent); }
.paper mark.nm { color: inherit; border-radius: 2px; cursor: pointer; padding: .05em 0; }
.paper mark.hl-yellow { background: var(--hl-y); }
.paper mark.hl-green { background: var(--hl-g); }
.paper mark.hl-blue { background: var(--hl-b); }
.paper mark.hl-pink { background: var(--hl-p); }
.paper mark.asked { background: color-mix(in srgb, var(--cd) 14%, transparent); box-shadow: inset 0 -2px 0 var(--cd); }
.flash { animation: rflash 1.4s ease-out; }
@keyframes rflash { 0%, 40% { background: color-mix(in srgb, var(--hi) 55%, transparent); } }

/* ✦ buttons on headings, equations and figures */
.htools { display: inline-flex; margin-left: .55em; vertical-align: middle; opacity: 0; transition: opacity .15s; }
.paper h2:hover .htools, .paper h3:hover .htools, .paper h4:hover .htools, .htools:focus-within { opacity: 1; }
.hbtn { display: inline-flex; align-items: center; gap: 5px; border: 1.5px solid var(--line); background: var(--surface); color: var(--cd); border-radius: 999px; padding: 3px 10px; font: 700 .72rem/1.3 var(--f-body); cursor: pointer; letter-spacing: 0; }
.hbtn:hover { border-color: var(--cd); }
.hbtn svg { width: 13px; height: 13px; }
.etools { position: absolute; top: 2px; right: 0; opacity: 0; transition: opacity .15s; }
.peq:hover .etools, .pmb:hover .etools, .etools:focus-within { opacity: 1; }
.ftools { margin-top: .6em; text-align: left; }
@media (hover: none) { .htools, .etools { opacity: 1; } .etools { position: static; text-align: right; } }

.refs details { margin-top: 2em; }
.refs summary { cursor: pointer; list-style: none; }
.refs summary::-webkit-details-marker { display: none; }
.refs summary h2 { display: inline; margin: 0; }
.refs summary::after { content: "Show"; font: 700 .7rem var(--f-mono); color: var(--muted); margin-left: .8em; text-transform: uppercase; letter-spacing: .1em; }
.refs details[open] summary::after { content: "Hide"; }
.reflist { font: .78em/1.5 var(--f-body); padding: 0; list-style: none; margin: 1em 0 0; }
.reflist li, .reflist p { margin: .45em 0; }

.pdfflow .cap { font: .8em/1.55 var(--f-body); color: var(--muted); background: var(--surface2); padding: .5em .8em; border-radius: 8px; }
.pdfflow .small { font-size: .8em; color: var(--muted); }
.pdfflow .peqi { font: .8em var(--f-mono); background: var(--surface2); padding: .05em .4em; border-radius: 5px; color: var(--ink); }
.pdfflow .frag { font: .72em/1.5 var(--f-mono); color: var(--muted); border-left: 2px dashed var(--line); padding-left: .9em; }

.rend { margin-top: 3em; padding: 22px; border: 2px dashed var(--line); border-radius: 14px; text-align: center; font-family: var(--f-body); font-size: 1rem; }
.rend h3 { margin: 0 0 .3em; font: 800 1.2rem var(--f-display); }
.rend-acts { display: flex; gap: 10px; justify-content: center; flex-wrap: wrap; margin-top: 12px; }

.rmsg { max-width: 580px; margin: 8vh auto; text-align: center; font-family: var(--f-body); font-size: 1rem; padding: 20px; border-radius: 16px; }
.rmsg h2 { font: 800 1.5rem var(--f-display); margin: 0 0 .5em; }
.rmsg p { margin: 0 0 .8em; }
.rspin { width: 40px; height: 40px; border-radius: 50%; border: 4px solid var(--surface2); border-top-color: var(--hi); animation: rspin 1s linear infinite; margin: 0 auto 14px; }
@keyframes rspin { to { transform: rotate(360deg); } }
.rmsg-acts { display: flex; flex-wrap: wrap; gap: 10px; justify-content: center; margin: 16px 0; }
.rmsg.drag { outline: 3px dashed var(--ca); outline-offset: 6px; }
.upl { cursor: pointer; }
.upl svg, .rmsg-acts svg { width: 18px; height: 18px; }

/* ---------- select text → ask bar, and the answer bubble (lessons and the reader) ---------- */
::highlight(lm-pending), ::highlight(lm-asked) { background-color: color-mix(in srgb, var(--cd) 28%, transparent); }
.askbar { position: fixed; z-index: 92; width: min(500px, calc(100vw - 16px)); background: var(--ink); color: var(--bg); border-radius: 14px; padding: 6px; box-shadow: 0 14px 38px rgba(0, 0, 0, .32); font-family: var(--f-body); }
.ab-row { display: flex; align-items: center; gap: 2px; }
.ab-form { flex: 1; min-width: 0; display: flex; align-items: center; gap: 6px; background: color-mix(in srgb, var(--bg) 13%, transparent); border-radius: 10px; padding: 0 4px 0 10px; }
.ab-form > svg { width: 16px; height: 16px; color: var(--hi); flex: none; }
.ab-in { flex: 1; min-width: 0; border: 0; background: none; color: inherit; font: inherit; font-size: .95rem; padding: 9px 2px; outline: none; }
.ab-in::placeholder { color: color-mix(in srgb, var(--bg) 62%, transparent); }
.ab-go { border: 0; width: 32px; height: 32px; border-radius: 9px; background: var(--hi); color: var(--hi-ink); display: grid; place-items: center; cursor: pointer; flex: none; }
.ab-go svg { width: 16px; height: 16px; }
.ab-x { border: 0; background: none; color: inherit; height: 36px; min-width: 32px; border-radius: 9px; display: inline-flex; align-items: center; justify-content: center; gap: 5px; cursor: pointer; padding: 0 6px; flex: none; font: 700 .85rem var(--f-body); }
.ab-x:hover { background: color-mix(in srgb, var(--bg) 16%, transparent); }
.ab-x svg { width: 17px; height: 17px; }
.ab-x.swb { min-width: 26px; padding: 0 4px; }
.ab-chips { display: flex; flex-wrap: wrap; gap: 5px; padding: 7px 2px 2px; }
.ab-chip { border: 1px solid color-mix(in srgb, var(--bg) 28%, transparent); background: none; color: inherit; border-radius: 999px; padding: 4px 10px; font-weight: 700; font-size: .78rem; cursor: pointer; }
.ab-chip:hover { background: color-mix(in srgb, var(--bg) 14%, transparent); }
.ab-suggest { display: flex; align-items: flex-start; gap: 9px; width: 100%; margin-bottom: 6px; border: 0; border-radius: 10px; background: var(--hi); color: var(--hi-ink); padding: 9px 11px; font: 700 .92rem/1.35 var(--f-body); text-align: left; cursor: pointer; }
.ab-suggest:hover { filter: brightness(1.06); }
.ab-suggest svg { width: 16px; height: 16px; flex: none; margin-top: 2px; }
.ab-suggest small { display: block; font-size: .68rem; font-weight: 800; letter-spacing: .06em; text-transform: uppercase; opacity: .72; margin-bottom: 1px; }
@media (max-width: 560px) { .ab-x.hlb span { display: none; } }

.abubble { position: fixed; z-index: 91; width: min(430px, calc(100vw - 16px)); display: flex; flex-direction: column; background: var(--surface); color: var(--ink); border: 1.5px solid var(--line); border-radius: 16px; box-shadow: 0 18px 50px rgba(0, 0, 0, .26); font-family: var(--f-body); }
.abubble::before { content: ""; position: absolute; left: calc(var(--ax, 50%) - 8px); width: 14px; height: 14px; background: var(--surface); border: 1.5px solid var(--line); transform: rotate(45deg); }
.abubble[data-side="below"]::before { top: -8.5px; border-right: 0; border-bottom: 0; }
.abubble[data-side="above"]::before { bottom: -8.5px; border-left: 0; border-top: 0; }
.abubble.dock::before { display: none; }
.bb-top { display: flex; align-items: center; gap: 8px; padding: 10px 8px 4px 14px; }
.bb-top > svg { width: 15px; height: 15px; color: var(--cd); flex: none; }
.bb-title { flex: 1; min-width: 0; font: 700 .7rem var(--f-mono); letter-spacing: .08em; text-transform: uppercase; color: var(--muted); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.bb-x { border: 0; background: none; width: 30px; height: 30px; border-radius: 8px; display: grid; place-items: center; color: var(--muted); cursor: pointer; flex: none; }
.bb-x:hover { background: var(--surface2); color: var(--ink); }
.bb-x svg { width: 16px; height: 16px; }
.bb-body { flex: 1; min-height: 0; overflow-y: auto; padding: 2px 14px 10px; }
.bb-thread { display: flex; flex-direction: column; gap: 6px; }
.bb-q { align-self: flex-end; max-width: 88%; margin: 6px 0 0; background: var(--ca); color: #fff; padding: 6px 11px; border-radius: 12px 12px 4px 12px; font-size: .86rem; font-weight: 700; }
.bb-a { font-size: .95rem; line-height: 1.55; }
.bb-a p, .bb-a ul, .bb-a ol { margin: 0 0 .55em; }
.bb-a ul, .bb-a ol { padding-left: 1.2em; }
.bb-extra { display: grid; gap: 8px; padding-top: 8px; }
.bb-extra .sws { margin: 0; }
.bb-note { width: 100%; font: inherit; font-size: .92rem; padding: 8px 10px; border-radius: 10px; border: 1.5px solid var(--line); background: var(--bg); color: var(--ink); resize: vertical; }
.bb-chips { display: flex; flex-wrap: wrap; gap: 6px; align-items: center; }
.bb-chips .linkb { margin-left: auto; font-size: .82rem; }
.bb-form { display: flex; gap: 6px; align-items: center; border-top: 1px solid var(--line); padding: 8px 8px 8px 12px; }
.bb-in { flex: 1; min-width: 0; border: 1.5px solid var(--line); background: var(--bg); color: var(--ink); border-radius: 10px; padding: 8px 10px; font: inherit; font-size: .92rem; }
.bb-in:focus, .bb-note:focus { outline: none; border-color: var(--ca); }
.askbar.dock, .abubble.dock { left: 8px !important; right: 8px; width: auto; top: auto !important; bottom: calc(10px + env(safe-area-inset-bottom, 0px)) !important; }
.abubble.dock { max-height: 64vh; }
.sw { display: inline-block; width: 15px; height: 15px; border-radius: 50%; border: 2px solid rgba(255, 255, 255, .75); }
.sw.yellow { background: #FFD84D; } .sw.green { background: #6ED492; } .sw.blue { background: #86B2FF; } .sw.pink { background: #FF94BC; }
.rpop.dock { left: 50% !important; right: auto; top: auto !important; bottom: calc(14px + env(safe-area-inset-bottom, 0px)); transform: translateX(-50%); }
.rpop { position: fixed; z-index: 91; width: min(390px, calc(100vw - 16px)); max-height: 62vh; overflow: auto; background: var(--surface); color: var(--ink); border: 1.5px solid var(--line); border-radius: 14px; padding: 14px; box-shadow: 0 16px 44px rgba(0, 0, 0, .28); font-family: var(--f-body); font-size: .95rem; }
.rpop .pk { font: 700 .68rem var(--f-mono); letter-spacing: .1em; text-transform: uppercase; color: var(--muted); margin: 0 0 6px; }
.rpop h4 { margin: 0 0 6px; font: 800 1.1rem var(--f-display); }
.rpop p { margin: 0 0 8px; }
.rpop textarea, .rside textarea { width: 100%; font: inherit; font-size: .95rem; padding: 9px 11px; border-radius: 12px; border: 1.5px solid var(--line); background: var(--bg); color: var(--ink); resize: vertical; }
.rpop textarea:focus, .rside textarea:focus { outline: none; border-color: var(--ca); }
.pacts { display: flex; gap: 6px; flex-wrap: wrap; margin-top: 8px; align-items: center; }
.askpop .aq { margin: 0 0 10px; padding: 8px 11px; border-left: 4px solid var(--cd); background: var(--surface2); border-radius: 8px; font: italic .9rem/1.5 "Literata", Georgia, serif; }
.chips, .nmore, .quick { display: flex; flex-wrap: wrap; gap: 6px; }
.askpop .chips { margin-bottom: 10px; }
.rchip { border: 1.5px solid var(--line); background: var(--bg); color: var(--ink); border-radius: 999px; padding: 5px 11px; font-weight: 700; font-size: .82rem; cursor: pointer; }
.rchip:hover { border-color: var(--cd); color: var(--cd); }
.askf { display: flex; gap: 8px; align-items: flex-end; }
.askf textarea { flex: 1; }
.sws { display: flex; gap: 4px; margin-bottom: 8px; }
.sws .swb { border: 2px solid transparent; border-radius: 50%; background: none; padding: 3px; cursor: pointer; display: grid; }
.sws .swb.on { border-color: var(--ink); }
.sws .sw { width: 22px; height: 22px; border-color: transparent; }

/* side panel */
.rside { border-left: 1px solid var(--line); background: var(--bg); display: flex; flex-direction: column; min-height: 0; font-family: var(--f-body); }
.rtabs { display: flex; align-items: center; gap: 2px; padding: 8px 10px 0; border-bottom: 1px solid var(--line); }
.rtab { border: 0; background: none; padding: 9px 10px; font-weight: 700; font-size: .92rem; color: var(--muted); cursor: pointer; border-bottom: 3px solid transparent; margin-bottom: -1px; }
.rtab[aria-selected="true"] { color: var(--ink); border-bottom-color: var(--hi); }
.rtab b { font: 700 .7rem var(--f-mono); background: var(--surface2); color: var(--ink); border-radius: 99px; padding: 1px 6px; margin-left: 2px; }
.rside-x { margin-left: auto; padding: 5px; border: 0; background: none; }
.rsbody { flex: 1; overflow-y: auto; padding: 14px; display: grid; gap: 12px; align-content: start; }
.rsfoot { border-top: 1px solid var(--line); padding: 10px 14px calc(10px + env(safe-area-inset-bottom, 0px)); font-size: .8rem; display: grid; gap: 3px; }
.rnotes-tools { display: flex; justify-content: flex-end; }
.rnotes-tools svg { width: 15px; height: 15px; }
.ncard { background: var(--surface); border: 1.5px solid var(--line); border-radius: 14px; padding: 10px 12px 12px; display: grid; gap: 8px; box-shadow: inset 4px 0 0 var(--cd); }
.ncard.c-yellow { box-shadow: inset 4px 0 0 #FFD84D; } .ncard.c-green { box-shadow: inset 4px 0 0 #6ED492; } .ncard.c-blue { box-shadow: inset 4px 0 0 #86B2FF; } .ncard.c-pink { box-shadow: inset 4px 0 0 #FF94BC; }
.ncard.flash { animation: rflash 1.2s; }
.nhead { display: flex; align-items: center; gap: 4px; }
.nk { flex: 1; font: 700 .68rem var(--f-mono); letter-spacing: .06em; text-transform: uppercase; color: var(--muted); overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.iconbtn { border: 0; background: none; width: 32px; height: 32px; border-radius: 8px; display: grid; place-items: center; color: var(--muted); cursor: pointer; flex: none; }
.iconbtn:hover { background: var(--surface2); color: var(--ink); }
.iconbtn svg { width: 17px; height: 17px; }
.nquote { margin: 0; padding: 4px 10px; border-left: 3px solid var(--line); color: var(--muted); font: italic .9rem/1.5 "Literata", Georgia, serif; }
.nquote.eqq { font-style: normal; overflow-x: auto; }
.nq, .nnote { margin: 0; font-size: .9rem; }
.nans { font-size: .95rem; line-height: 1.55; }
.nans p, .nans ul, .nans ol { margin: 0 0 .6em; }
.nans ul, .nans ol, .md ul, .md ol { padding-left: 1.2em; }
.md h4 { font: 800 1rem var(--f-display); margin: 1em 0 .4em; }
.dmath { overflow-x: auto; text-align: center; margin: .4em 0; }
code.tex { font: .85em var(--f-mono); background: var(--surface2); padding: 1px 4px; border-radius: 4px; }
.rempty { color: var(--muted); font-size: .92rem; text-align: center; padding: 18px 8px; }
.rempty b { color: var(--ink); }
.rempty p { margin: 0 0 .6em; }
.rprep { background: var(--surface); border: 1.5px solid var(--line); border-radius: 14px; padding: 12px 14px; }
.rprep p { margin: 0 0 8px; }
.rprep .pk, .rquiz .pk { font: 700 .68rem var(--f-mono); letter-spacing: .1em; text-transform: uppercase; color: var(--muted); }
.rguide { font-size: .95rem; }
.qrow { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; }
.qrow select { flex: 1; min-width: 0; font: inherit; font-size: .9rem; padding: 8px; border-radius: 10px; border: 1.5px solid var(--line); background: var(--surface); color: var(--ink); }
.rquiz { display: grid; gap: 16px; }
.qq { display: grid; gap: 6px; }
.qq .qt { font-weight: 700; margin: 0 0 4px; }
.opt.sm { padding: 9px 12px; font-size: .92rem; box-shadow: 0 2px 0 var(--line); border-radius: 12px; }
.qres { font-weight: 700; margin: 0; }
.rside .chat { display: grid; gap: 10px; }
.rside .msg { font-size: .94rem; max-width: 100%; }
.rside .msg.ai p { margin: 0 0 .5em; }

/* figure zoom and PDF page view */
.zoom { position: fixed; inset: 0; z-index: 95; background: rgba(8, 12, 16, .86); display: grid; place-items: center; padding: 20px; cursor: zoom-out; }
.zoom img { max-width: 100%; max-height: 100%; background: #fff; border-radius: 8px; }
.zx { position: absolute; top: calc(14px + env(safe-area-inset-top, 0px)); right: 14px; }
.pages { display: grid; gap: 16px; }
.pvnote { margin: 0; font: .85em/1.5 var(--f-body); color: var(--muted); text-align: center; }
.pg { position: relative; background: #fff; border-radius: 6px; box-shadow: var(--shadow); overflow: hidden; width: 100%; }
.pg canvas { position: absolute; inset: 0; width: 100%; height: 100%; }
.textLayer { position: absolute; text-align: initial; inset: 0; overflow: hidden; opacity: 1; line-height: 1; -webkit-text-size-adjust: none; text-size-adjust: none; forced-color-adjust: none; transform-origin: 0 0; z-index: 2; }
.textLayer :is(span, br) { color: transparent; position: absolute; white-space: pre; cursor: text; transform-origin: 0% 0%; }
.textLayer span.markedContent { top: 0; height: 0; }
.textLayer ::selection { background: rgba(0, 90, 255, .28); }
.textLayer br::selection { background: transparent; }

/* narrower screens */
@media (min-width: 1181px) { .rt-toc { display: none; } }
@media (max-width: 1180px) {
  .rwrap, .reader:not(.side-open) .rwrap { grid-template-columns: minmax(0, 1fr) 390px; }
  .reader:not(.side-open) .rwrap { grid-template-columns: minmax(0, 1fr); }
  .rtoc { position: fixed; top: 0; left: 0; bottom: 0; width: min(310px, 86vw); z-index: 86; transform: translateX(-104%); transition: transform .2s ease-out; box-shadow: 10px 0 40px rgba(0, 0, 0, .2); padding-top: calc(18px + env(safe-area-inset-top, 0px)); }
  .reader.toc-open .rtoc { transform: none; }
}
@media (max-width: 900px) {
  .rwrap, .reader:not(.side-open) .rwrap { grid-template-columns: minmax(0, 1fr); }
  .rside, .reader:not(.side-open) .rside { display: flex; position: fixed; left: 0; right: 0; bottom: 0; height: min(74vh, 660px); z-index: 85; border-left: 0; border-top: 1.5px solid var(--line); border-radius: 18px 18px 0 0; box-shadow: 0 -12px 40px rgba(0, 0, 0, .25); transform: translateY(105%); transition: transform .22s ease-out; }
  .reader.side-open .rside { transform: none; }
  .rtools .rbtn span, .rback span { display: none; }
  .rsize { display: none; }
  .rstage { padding: 12px 8px 140px; }
  .paper { border-radius: 10px; padding: 20px 16px; }
}
@media (prefers-reduced-motion: reduce) { .rtoc, .rside { transition: none; } }

/* ---------- circle to ask (circle.js): a loop drawn over the screen, kept while its answer is open ---------- */
.circle-layer { position: fixed; inset: 0; z-index: 90; pointer-events: none; }
.circle-layer.drawing { pointer-events: auto; cursor: crosshair; touch-action: none; background: color-mix(in srgb, var(--ink) 6%, transparent); }
.circle-layer svg { position: absolute; inset: 0; width: 100%; height: 100%; overflow: visible; transition: opacity .25s; }
.circle-layer.gone svg { opacity: 0; }
.cl-halo { fill: color-mix(in srgb, var(--hi) 16%, transparent); stroke: color-mix(in srgb, var(--hi) 40%, transparent); stroke-width: 14; stroke-linejoin: round; stroke-linecap: round; }
.cl-line { fill: none; stroke: color-mix(in srgb, var(--hi) 80%, var(--ink)); stroke-width: 3.5; stroke-linejoin: round; stroke-linecap: round; }
.cl-hint { position: absolute; top: calc(14px + env(safe-area-inset-top, 0px)); left: 50%; transform: translateX(-50%); display: flex; align-items: center; gap: 12px; width: max-content; max-width: calc(100vw - 24px); background: var(--ink); color: var(--bg); padding: 6px 6px 6px 16px; border-radius: 99px; font: 600 .9rem var(--f-body); box-shadow: 0 10px 30px rgba(0, 0, 0, .25); }
.cl-x { border: 0; background: color-mix(in srgb, var(--bg) 20%, transparent); color: inherit; border-radius: 99px; padding: 0 16px; min-height: 44px; font: inherit; cursor: pointer; flex: none; }
.circleb svg { color: var(--cb) !important; }
/* a lesson's header on a small phone: Circle is its icon alone, so Close, the progress, Circle and Tutor fit */
@media (max-width: 420px) { .player > .phead .circleb { width: 44px; padding: 0; justify-content: center; flex: none; } .player > .phead .circleb span { display: none; } }