/* GroundUp Lab reader — one stylesheet, light and dark by token swap.
   Shared design system with the lesson pages: nothing below hard-codes a colour. */

:root{
  --paper:#fdfdfb; --ink:#151a1d; --ink-2:#4b555b; --ink-3:#7d868b;
  --rule:#dde1dd; --surface:#f4f6f3; --surface-2:#eaeee9;
  --grid:#e3e7e3; --axis:#a8b0aa;
  --u:#bf3b22; --v:#166b7b; --w:#9d7310;
  --accent:#166b7b; --accent-soft:#dfeaec; --warn:#a8491a;
  --shadow:0 1px 2px rgba(20,30,28,.06), 0 8px 24px rgba(20,30,28,.05);
  --serif:"Spectral",Iowan Old Style,Georgia,serif;
  --sans:"IBM Plex Sans",-apple-system,BlinkMacSystemFont,Segoe UI,sans-serif;
  --mono:"IBM Plex Mono",ui-monospace,SFMono-Regular,Menlo,monospace;
  color-scheme:light;
}
@media (prefers-color-scheme:dark){
  :root:not([data-theme="light"]){
    --paper:#0f1214; --ink:#e7eae6; --ink-2:#9ba4a7; --ink-3:#6c7579;
    --rule:#262b2d; --surface:#161a1c; --surface-2:#1e2325;
    --grid:#222829; --axis:#3f4749;
    --u:#e8674a; --v:#4fb4c5; --w:#d6a542;
    --accent:#4fb4c5; --accent-soft:#12292e; --warn:#dd8a4e;
    --shadow:0 1px 2px rgba(0,0,0,.4), 0 8px 24px rgba(0,0,0,.3);
    color-scheme:dark;
  }
}
:root[data-theme="dark"]{
  --paper:#0f1214; --ink:#e7eae6; --ink-2:#9ba4a7; --ink-3:#6c7579;
  --rule:#262b2d; --surface:#161a1c; --surface-2:#1e2325;
  --grid:#222829; --axis:#3f4749;
  --u:#e8674a; --v:#4fb4c5; --w:#d6a542;
  --accent:#4fb4c5; --accent-soft:#12292e; --warn:#dd8a4e;
  --shadow:0 1px 2px rgba(0,0,0,.4), 0 8px 24px rgba(0,0,0,.3);
  color-scheme:dark;
}

*{box-sizing:border-box}
[hidden]{display:none!important}
html,body{margin:0}
body{background:var(--paper);color:var(--ink);font-family:var(--serif);font-size:17px;line-height:1.62;-webkit-font-smoothing:antialiased}
img{max-width:100%}
a{color:var(--accent);text-underline-offset:4px}
:focus-visible{outline:2px solid var(--accent);outline-offset:2px}

/* ------------------------------------------------------------ chrome -- */
/* site header, footer, landing and status pages: see site.css */
.layout{display:grid;grid-template-columns:288px minmax(0,1fr)}
aside{padding:26px 20px;border-right:1px solid var(--rule);background:var(--surface);position:sticky;top:0;max-height:100vh;overflow:auto;font-family:var(--sans)}
aside h1{font-family:var(--serif);font-size:23px;line-height:1.2;letter-spacing:-.015em;margin:0 0 4px}
aside .muted{margin:0 0 18px}
nav h2{font-size:10.5px;letter-spacing:.11em;text-transform:uppercase;color:var(--ink-3);font-weight:600;margin:22px 0 6px}
nav a{display:block;font-size:13px;line-height:1.45;padding:7px 9px;text-decoration:none;border-radius:5px;color:var(--ink-2)}
nav a:hover{background:var(--surface-2);color:var(--ink)}
nav a[aria-current=page]{background:var(--accent-soft);color:var(--ink);font-weight:500}
main{min-width:0;max-width:1000px;padding:30px 28px 90px}
.toolbar{position:sticky;top:0;z-index:12;display:flex;gap:8px;flex-wrap:wrap;align-items:center;
  font-family:var(--sans);font-size:13px;margin:0 -28px 26px;padding:10px 28px;
  background:color-mix(in srgb,var(--paper) 92%,transparent);backdrop-filter:blur(6px);
  border-bottom:1px solid var(--rule)}
#status,.muted,#saved{color:var(--ink-3);font-family:var(--sans);font-size:12.5px}
#status{margin:0 0 14px;letter-spacing:.02em}

button{font-family:var(--sans);font-size:12px;font-weight:500;padding:6px 11px;border:1px solid var(--rule);background:var(--paper);color:var(--ink);border-radius:5px;cursor:pointer}
button:hover{border-color:var(--accent);color:var(--accent)}
button:disabled{opacity:.45;cursor:default}
button.primary{background:var(--accent);color:var(--paper);border-color:var(--accent)}
button.primary:hover{opacity:.88;color:var(--paper)}
input,textarea,select{font-family:var(--sans)}
input[type=search],textarea{width:100%;background:var(--paper);color:var(--ink);border:1px solid var(--rule);border-radius:5px;padding:9px 10px;font-size:13px}
input[type=checkbox]{accent-color:var(--accent);margin-right:8px}
aside label{display:block;font-size:11.5px;letter-spacing:.06em;text-transform:uppercase;color:var(--ink-3);margin:0 0 6px}

/* ------------------------------------------------------------ article -- */
article{max-width:680px}
article h1{font-family:var(--serif);font-weight:700;font-size:clamp(28px,4.4vw,42px);line-height:1.1;letter-spacing:-.018em;margin:0 0 20px;text-wrap:balance}
article h2{font-family:var(--serif);font-weight:600;font-size:clamp(22px,3.2vw,29px);line-height:1.22;letter-spacing:-.012em;margin:52px 0 18px;padding-top:26px;border-top:1px solid var(--rule);text-wrap:balance}
article h3{font-family:var(--sans);font-weight:600;font-size:15px;margin:30px 0 10px}
article h4{font-family:var(--sans);font-weight:600;font-size:13px;letter-spacing:.05em;text-transform:uppercase;color:var(--ink-3);margin:26px 0 8px}
article p{margin:0 0 16px}
article ul,article ol{margin:0 0 16px;padding-left:22px}
article li{margin-bottom:7px}
article hr{border:none;border-top:1px solid var(--rule);margin:34px 0}
article strong{font-weight:600}
code{font-family:var(--mono);font-size:.87em;background:var(--surface-2);padding:1px 5px;border-radius:3px}
article pre{font-family:var(--mono);font-size:12.5px;line-height:1.62;background:var(--surface-2);border:1px solid var(--rule);border-radius:6px;padding:13px 15px;overflow-x:auto;margin:0 0 16px}
article pre code{background:none;padding:0;font-size:inherit}
.katex{font-size:1.02em}
.katex-display{overflow-x:auto;overflow-y:hidden;padding-block:4px}
article table{display:block;overflow-x:auto;border-collapse:collapse;width:100%;font-size:14.5px;margin:0 0 18px}
article th,article td{text-align:left;padding:8px 10px;border-bottom:1px solid var(--rule);vertical-align:top}
article th{font-family:var(--sans);font-size:11.5px;letter-spacing:.06em;text-transform:uppercase;color:var(--ink-3);font-weight:600}
article img,article svg{max-width:100%;height:auto;border-radius:8px}

/* practice prompts and asides arrive as blockquotes; treat them as callouts */
article blockquote{margin:22px 0;padding:14px 18px;border:none;border-left:2px solid var(--rule);background:var(--surface);border-radius:0 5px 5px 0;font-size:15.5px;color:var(--ink-2)}
article blockquote > :last-child{margin-bottom:0}
article blockquote strong{font-family:var(--sans);font-size:12.5px;letter-spacing:.02em}

details{margin:14px 0;border:1px solid var(--rule);border-radius:5px;background:var(--surface)}
summary{cursor:pointer;padding:8px 12px;font-family:var(--sans);font-size:12px;font-weight:500;color:var(--ink-2);list-style:none}
summary::-webkit-details-marker{display:none}
summary::before{content:"▸ ";color:var(--accent)}
details[open] summary::before{content:"▾ "}
details[open] summary{border-bottom:1px solid var(--rule)}
details > :not(summary){padding-inline:14px}
details > :last-child{padding-bottom:12px}
.inline-lab-button{margin:2px}

/* --------------------------------------------------------------- labs -- */
.lab{position:relative;margin:30px 0;border:1px solid var(--rule);border-radius:8px;background:var(--surface);overflow:hidden;box-shadow:var(--shadow)}
.lab-head{padding:13px 16px;border-bottom:1px solid var(--rule);display:flex;align-items:baseline;gap:10px;flex-wrap:wrap}
.lab-title{font-family:var(--sans);font-weight:600;font-size:13.5px}
.lab-hint{font-family:var(--sans);font-size:12px;color:var(--ink-3)}
.lab-body{display:grid;grid-template-columns:minmax(0,1.45fr) minmax(0,1fr)}
.stage{position:relative;background:var(--paper);min-height:320px;aspect-ratio:1/1;max-width:100%}
.stage canvas{display:block;width:100%;height:100%;touch-action:none;cursor:crosshair}
.panel{padding:16px;border-left:1px solid var(--rule);font-family:var(--sans);font-size:13px;display:flex;flex-direction:column;gap:14px}
.ctl label{display:flex;justify-content:space-between;align-items:baseline;gap:8px;margin-bottom:5px;color:var(--ink-2);font-size:12px}
.ctl .val{font-family:var(--mono);font-size:12px;color:var(--ink);font-variant-numeric:tabular-nums}
input[type=range]{width:100%;accent-color:var(--accent);margin:0}
.readout{font-family:var(--mono);font-size:12.5px;line-height:1.75;font-variant-numeric:tabular-nums;background:var(--surface-2);border-radius:5px;padding:10px 12px;overflow-x:auto;white-space:pre-wrap}
.readout .k{color:var(--ink-3)}
.swatch{display:inline-block;width:9px;height:9px;border-radius:2px;margin-right:6px}
.verdict{font-size:12.5px;padding:9px 11px;border-radius:5px;line-height:1.45;background:var(--accent-soft);color:var(--ink)}
.verdict.bad{background:color-mix(in srgb,var(--warn) 16%,transparent)}
.btnrow{display:flex;gap:7px;flex-wrap:wrap}
.togg{display:flex;align-items:center;gap:7px;font-size:12px;color:var(--ink-2)}
.togg input{accent-color:var(--accent)}
.lab-missing{font-family:var(--sans);font-size:13px;color:var(--warn);padding:16px;margin:22px 0;border:1px dashed var(--rule);border-radius:8px}
@media (max-width:760px){.lab-body{grid-template-columns:1fr}.stage{aspect-ratio:1/.92}.panel{border-left:none;border-top:1px solid var(--rule)}}

/* the elimination bench is a DOM lab rather than a canvas one */
.elim-body{display:grid;grid-template-columns:minmax(0,1.3fr) minmax(0,1fr)}
.elim-stage{padding:18px 16px;background:var(--paper);display:flex;flex-direction:column;gap:14px;min-width:0}
.mat{display:flex;align-items:stretch;gap:9px;font-family:var(--mono);overflow-x:auto;padding-bottom:2px}
.mat .rail{width:8px;border:1.6px solid var(--ink-3);border-right:none;border-radius:3px 0 0 3px;flex:none}
.mat .rail.r{border:1.6px solid var(--ink-3);border-left:none;border-radius:0 3px 3px 0}
.cells{display:grid;gap:5px 7px;flex:none}
.cells input{width:62px;padding:5px 4px;text-align:center;font-family:var(--mono);font-size:13.5px;color:var(--ink);
  background:var(--surface);border:1px solid var(--rule);border-radius:4px;font-variant-numeric:tabular-nums}
.cells input.aug{background:var(--accent-soft);border-color:color-mix(in srgb,var(--accent) 35%,var(--rule))}
.cells input.piv{border-color:var(--u);color:var(--u);font-weight:600}
.oprow{display:flex;gap:6px;align-items:center;flex-wrap:wrap;font-family:var(--sans);font-size:12px;color:var(--ink-2)}
.oprow select,.oprow input[type=number]{font-family:var(--mono);font-size:12px;padding:4px 6px;border:1px solid var(--rule);
  border-radius:4px;background:var(--paper);color:var(--ink)}
.oprow input[type=number]{width:64px}
.log{font-family:var(--mono);font-size:11.5px;color:var(--ink-3);line-height:1.6;max-height:96px;overflow-y:auto;
  border-top:1px dashed var(--rule);padding-top:8px}
.log div:first-child{color:var(--ink-2)}
.verdict.warnish{background:color-mix(in srgb,var(--w) 18%,transparent)}
@media (max-width:760px){.elim-body{grid-template-columns:1fr}}

/* -------------------------------------------------- anchored ask notes -- */
.anch{position:relative}
.askchip{display:inline-flex;align-items:center;justify-content:center;width:20px;height:20px;margin-left:7px;vertical-align:-4px;padding:0;border:1px solid var(--rule);border-radius:5px;background:var(--paper);color:var(--ink-3);font-family:var(--sans);font-size:11px;font-weight:600;line-height:1;cursor:pointer;opacity:.3;transition:opacity .15s,border-color .15s,color .15s}
.anch:hover > .askchip,.askchip:focus-visible{opacity:1}
.askchip:hover{border-color:var(--w);color:var(--w)}
.askchip.has{opacity:1;border-color:var(--w);color:var(--w);background:color-mix(in srgb,var(--w) 12%,transparent)}
.anch-block > .askchip{position:absolute;top:9px;right:9px;margin:0;z-index:2}
.lab.anch-block > .askchip{top:11px;right:12px}
.gu-note{max-width:680px;margin:14px 0 22px;border:1px solid var(--rule);border-left:3px solid var(--w);border-radius:0 7px 7px 0;background:color-mix(in srgb,var(--w) 7%,var(--surface));font-family:var(--sans);font-size:14px;overflow:hidden}
.note-h{display:flex;align-items:center;gap:8px;padding:8px 11px;border-bottom:1px solid var(--rule)}
.note-h .lbl{font-size:10.5px;letter-spacing:.11em;text-transform:uppercase;font-weight:600;color:var(--w)}
.note-h .exc{flex:1;min-width:0;font-size:11.5px;color:var(--ink-3);white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.note-h .close{border:none;background:none;color:var(--ink-3);font-size:15px;padding:2px 6px}
.note-h .close:hover{color:var(--warn);border:none}
.note-thread{display:flex;flex-direction:column;gap:11px;padding:12px 13px}
.note-thread:empty{display:none}
.turn{font-size:14.5px;line-height:1.55}
.turn .who{font-size:10.5px;letter-spacing:.1em;text-transform:uppercase;font-weight:600;display:block;margin-bottom:3px}
.turn.me .who{color:var(--v)}
.turn.cl .who{color:var(--u)}
.turn .body{white-space:pre-wrap;color:var(--ink)}
.turn.me .body{color:var(--ink-2)}
.note-compose{padding:11px 13px;border-top:1px solid var(--rule);display:flex;flex-direction:column;gap:8px}
.note-compose textarea{min-height:62px;resize:vertical;font-size:14px;line-height:1.5}
.note-actions{display:flex;align-items:center;gap:8px;flex-wrap:wrap}
.note-status{font-size:12px;color:var(--ink-3)}
.note-status.err{color:var(--warn)}
.flash{animation:fl 1.4s ease-out}
@keyframes fl{0%{background:color-mix(in srgb,var(--w) 26%,transparent)}100%{background:transparent}}

#guRail{position:fixed;right:14px;bottom:14px;z-index:40;font-family:var(--sans);padding-bottom:env(safe-area-inset-bottom,0px)}
#guRail .pill{display:flex;align-items:center;gap:7px;font-size:12.5px;font-weight:500;padding:8px 13px;border-radius:100px;border:1px solid var(--rule);background:var(--surface);color:var(--ink);box-shadow:var(--shadow)}
#guRail .pill .n{font-family:var(--mono);color:var(--w)}
#guList{position:absolute;right:0;bottom:48px;width:min(320px,calc(100vw - 32px));max-height:52vh;overflow-y:auto;background:var(--surface);border:1px solid var(--rule);border-radius:8px;box-shadow:var(--shadow);padding:6px}
#guList a{display:block;padding:7px 9px;border-radius:5px;font-size:12.5px;line-height:1.4;color:var(--ink-2);text-decoration:none}
#guList a:hover{background:var(--surface-2);color:var(--ink)}

.gu-modal{width:min(460px,92vw);border:1px solid var(--rule);border-radius:10px;background:var(--paper);color:var(--ink);box-shadow:var(--shadow);padding:20px;font-family:var(--sans)}
.gu-modal::backdrop{background:rgba(10,14,16,.5)}
.gu-modal h2{font-family:var(--sans);font-size:16px;font-weight:600;margin:0 0 6px}
.gu-modal .fine{font-size:12px;color:var(--ink-3);line-height:1.5;margin:0 0 16px}
.gu-modal label{display:block;font-size:12px;color:var(--ink-2);margin:12px 0 4px}
.gu-modal label.inline{display:flex;align-items:center;gap:8px;margin-top:10px}
.gu-modal input,.gu-modal select{width:100%;font-size:13px;padding:7px 9px;border:1px solid var(--rule);border-radius:5px;background:var(--surface);color:var(--ink)}
.gu-modal .row{display:flex;gap:7px;align-items:stretch}
.gu-modal .row button{white-space:nowrap}
.gu-modal-actions{display:flex;justify-content:flex-end;gap:8px;margin-top:20px}
.tutor-connect{font-size:12px}
.progress-line{margin-left:auto;font-size:12px;color:var(--ink-3);font-variant-numeric:tabular-nums}
button.mini{font-size:11.5px;padding:4px 9px}
.list-tools{display:flex;gap:6px;flex-wrap:wrap;padding:8px 9px 4px;border-top:1px solid var(--rule);margin-top:6px}
.list-empty{margin:0;padding:10px 9px;font-size:12.5px;color:var(--ink-3);line-height:1.45}

/* --------------------------------------------------------- python lab -- */
.practice{border-top:1px solid var(--rule);margin-top:52px;padding-top:24px;max-width:680px}
.practice h2{font-family:var(--serif);font-weight:600;font-size:24px;margin:0 0 8px}
.practice label{display:block;margin:12px 0;font-family:var(--sans);font-size:13px;color:var(--ink-2)}
.python-lab{position:fixed;z-index:30;inset:0 0 0 auto;width:min(94vw,620px);margin:0;padding:24px;border:0;border-left:1px solid var(--rule);background:var(--surface);box-shadow:var(--shadow);overflow-y:auto;overscroll-behavior:contain;font-family:var(--sans)}
.python-lab-heading{display:flex;justify-content:space-between;gap:20px;align-items:start}
.python-lab-heading h2{font-family:var(--serif);font-size:22px;margin:0}
.python-lab-heading .eyebrow{margin:0 0 4px;color:var(--ink-3);font-size:10.5px;font-weight:600;letter-spacing:.11em;text-transform:uppercase}
.python-lab-meta{display:flex;align-items:center;gap:8px;flex-wrap:wrap;justify-content:flex-end}
.python-lab-heading span{background:var(--accent-soft);color:var(--ink);border-radius:999px;padding:4px 10px;font:12px/1.4 var(--mono)}
.python-lab-meta #python-close{display:grid;place-items:center;width:32px;height:32px;padding:0;border-radius:50%;font-size:20px;line-height:1}
.python-lab p{font-size:13px;color:var(--ink-2)}
.python-tabs{display:flex;gap:7px;overflow-x:auto;margin:18px 0 4px;padding-bottom:5px}
.python-tabs button{white-space:nowrap}
.python-tabs button[aria-pressed=true]{background:var(--accent-soft);border-color:var(--accent);color:var(--ink)}
.python-lab label{display:block;margin:14px 0 6px;font-size:11.5px;letter-spacing:.06em;text-transform:uppercase;color:var(--ink-3)}
.python-lab textarea{min-height:360px;resize:vertical;tab-size:4;font:13px/1.55 var(--mono);white-space:pre;background:var(--paper)}
.python-actions{display:flex;gap:8px;flex-wrap:wrap;margin-top:12px}
.python-actions button span{font-size:11px;color:var(--ink-3);margin-left:4px}
.python-actions .danger-muted{margin-left:auto;border-color:color-mix(in srgb,var(--warn) 45%,var(--rule));color:var(--warn)}
.python-lab pre{min-height:100px;max-height:360px;overflow:auto;margin:6px 0 0;background:var(--surface-2);border:1px solid var(--rule);padding:13px 15px;border-radius:6px;font:12.5px/1.6 var(--mono);color:var(--ink);white-space:pre-wrap}
.python-lab pre.pass{border-color:color-mix(in srgb,var(--accent) 55%,var(--rule))}
.python-lab pre.fail{border-color:color-mix(in srgb,var(--warn) 55%,var(--rule));color:var(--warn)}
body.lab-open{overflow-x:hidden}
.mermaid{text-align:center}

@media(min-width:1300px){body.lab-open .layout{padding-right:clamp(420px,38vw,620px)}.python-lab{width:clamp(420px,38vw,620px)}}
@media(max-width:850px){.layout{display:block}.toolbar{margin-inline:-20px;padding-inline:20px}aside{position:static;max-height:none;border-right:0;border-bottom:1px solid var(--rule)}main{padding:24px 20px 70px}}
@media(max-width:600px){.python-lab{padding:16px}.python-lab-heading{display:block}.python-lab-meta{justify-content:flex-start;margin-top:10px}.python-actions .danger-muted{margin-left:0}}
@media (prefers-reduced-motion:reduce){*{animation:none !important;transition:none !important}}
@media print{
  header,footer,aside,.toolbar,.practice,.python-lab,#status,#guRail,.askchip,.gu-modal,.panel,#lesson-banner{display:none}
  .layout{display:block}main{max-width:none;padding:0}
  article pre{white-space:pre-wrap}
  .stage{aspect-ratio:auto;height:320px}
}


/* ------------------------------------------------------------ exercises -- */
.exgrid{margin:22px 0;border:1px solid var(--rule);border-radius:8px;background:var(--surface);overflow:hidden}
.ex{padding:18px 20px;margin:0;border-top:1px solid var(--rule)}
.ex:first-child{border-top:none}
.ex-head{display:flex;align-items:baseline;flex-wrap:wrap;gap:8px;margin-bottom:9px}
.ex-h.ex-id{font-family:var(--mono);font-size:12px;font-weight:600;letter-spacing:.04em;color:var(--accent)}
.ex-tag{font-family:var(--sans);font-size:10px;letter-spacing:.09em;text-transform:uppercase;font-weight:600;
  padding:2px 7px;border-radius:100px;border:1px solid var(--rule);color:var(--ink-3);background:var(--paper)}
.ex-tag.lvl-foundation{color:var(--v);border-color:color-mix(in srgb,var(--v) 40%,var(--rule))}
.ex-tag.lvl-core{color:var(--accent);border-color:color-mix(in srgb,var(--accent) 40%,var(--rule))}
.ex-tag.lvl-stretch{color:var(--w);border-color:color-mix(in srgb,var(--w) 45%,var(--rule))}
.ex-tag.lvl-checkpoint{color:var(--u);border-color:color-mix(in srgb,var(--u) 40%,var(--rule))}
.ex-name{font-family:var(--sans);font-size:12.5px;color:var(--ink-2);flex:1 1 auto;min-width:0}
.ex > p{margin:0 0 10px}
.ex > :last-child{margin-bottom:0}
.ex pre,.ex details{margin:10px 0 0}
.ex ul,.ex ol{margin:0 0 10px;padding-left:20px}

/* per-section practice, in the same vocabulary as the exercise bank */
.practice-set{margin:22px 0;padding:14px 16px;border:1px solid var(--rule);border-left:2px solid var(--accent);
  border-radius:0 6px 6px 0;background:var(--surface)}
.practice-cap{display:block;font-family:var(--sans);font-size:10.5px;letter-spacing:.11em;text-transform:uppercase;
  font-weight:600;color:var(--accent);margin-bottom:10px}
.practice-row{display:grid;grid-template-columns:92px minmax(0,1fr);gap:12px;align-items:baseline;margin-bottom:10px}
.practice-row:last-child{margin-bottom:0}
.practice-row > p{margin:0;font-size:15.5px;line-height:1.55}
.practice-row .ex-tag{justify-self:start;align-self:start}
.hintchip{margin-left:6px;padding:1px 8px;border:1px solid var(--rule);border-radius:100px;background:var(--paper);
  color:var(--ink-3);font-family:var(--sans);font-size:10.5px;letter-spacing:.06em;text-transform:uppercase;
  font-weight:600;line-height:1.6;vertical-align:1px;opacity:.45;transition:opacity .15s,color .15s,border-color .15s}
.practice-row:hover .hintchip,.hintchip:focus-visible{opacity:1}
.hintchip:hover{border-color:var(--accent);color:var(--accent)}
.practice-row .gu-note{grid-column:1/-1;margin-top:10px}
.practice-hint{grid-column:2;margin:0;font-size:14px;line-height:1.55}
.practice-hint summary{width:fit-content;cursor:pointer;color:var(--accent);font-family:var(--sans);font-size:12px}
.practice-hint p{margin:8px 0 0;padding:10px 12px;border-left:2px solid var(--accent);background:var(--surface)}
@media (max-width:520px){.practice-hint{grid-column:1}}
@media (max-width:520px){.practice-row{grid-template-columns:1fr;gap:5px}}

/* ------------------------------------------------------- answer checking -- */
.chk{margin-top:14px;padding-top:13px;border-top:1px dashed var(--rule);font-family:var(--sans);font-size:13px}
.chk-fields{display:grid;grid-template-columns:minmax(110px,max-content) minmax(0,1fr) 18px;gap:8px 10px;align-items:center;margin-bottom:12px}
.chk-f{display:contents}
@media (max-width:520px){.chk-fields{grid-template-columns:minmax(0,1fr) 18px}
  .chk-f label{grid-column:1/-1;margin-bottom:-4px}}
.chk-f label{font-size:12.5px;color:var(--ink-2)}
.chk-f [data-in]{font-family:var(--mono);font-size:12.5px;padding:5px 8px;border:1px solid var(--rule);
  border-radius:4px;background:var(--paper);color:var(--ink);width:100%;min-width:0}
.chk-f select[data-in]{font-family:var(--sans)}
.chk-f .chk-mk{font-size:14px;font-weight:700;text-align:center}
.chk-f.ok [data-in]{border-color:var(--v)} .chk-f.ok .chk-mk{color:var(--v)}
.chk-f.no [data-in]{border-color:var(--warn)} .chk-f.no .chk-mk{color:var(--warn)}
.chk-actions{display:flex;gap:7px;align-items:center;flex-wrap:wrap}
.chk-msg{font-size:12.5px;color:var(--ink-3);flex:1 1 180px;min-width:0}
.chk-msg.ok{color:var(--v)} .chk-msg.no{color:var(--warn)}
.chk-msg .h{color:var(--ink-2);display:block;margin-top:2px}
.chk-skip{border:none;background:none;color:var(--ink-3);font-size:11.5px;text-decoration:underline;padding:4px 2px}
.chk-skip:hover{border:none;color:var(--warn)}
.chk-work{margin-top:10px}
.chk-work textarea{width:100%;font-family:var(--sans);font-size:13.5px;line-height:1.5;padding:9px 10px;
  border:1px solid var(--rule);border-radius:5px;background:var(--paper);color:var(--ink);resize:vertical}
.chk-out{margin-top:10px;padding:11px 12px;border-radius:5px;background:var(--surface-2);
  white-space:pre-wrap;font-size:13.5px;line-height:1.55}
.chk-solution{margin-top:12px;padding:14px 16px;border-radius:5px;border-left:2px solid var(--v);
  background:var(--surface);font-family:var(--serif);font-size:15.5px;line-height:1.6}
.chk-solution .sol-tag{font-family:var(--sans);font-size:10.5px;letter-spacing:.11em;text-transform:uppercase;
  font-weight:600;color:var(--v);display:block;margin-bottom:8px}
.chk-solution p{margin:0 0 12px} .chk-solution > :last-child{margin-bottom:0}
.chk-solution ul{margin:0 0 12px;padding-left:20px}
.chk-solution pre{font-size:12px;margin-bottom:12px}
.sol-note{margin-top:14px;padding:11px 13px;border-radius:5px;background:var(--surface-2);
  font-family:var(--sans);font-size:13px;line-height:1.55;color:var(--ink-2)}
.sol-note strong{color:var(--ink)}

/* Linked data and observation views in the projection module. */
.lsq-views{display:grid;grid-template-columns:repeat(2,minmax(0,1fr))}
.lab-view-caption{padding:10px 14px;font:12px/1.5 var(--sans);color:var(--ink-3);border-bottom:1px solid var(--rule)}
.lsq-views .stage{min-height:280px}
.lsq-views + .panel{border-left:none;border-top:1px solid var(--rule)}
.lab .panel input[type="range"]{max-width:100%;display:block;width:100%}
@media(max-width:760px){.lsq-views{grid-template-columns:1fr}}

.qr-controls label{display:flex;align-items:center;gap:6px}
.qr-controls select{padding:4px 6px;border:1px solid var(--rule);border-radius:4px;background:var(--paper);color:var(--ink)}
.lab[data-lab="la-gramschmidt"] .readout table{margin:0;font-size:12px;white-space:normal}

/* Linked quadratic-form views keep chart captions and traces compact. */
.quadform-views .quadform-caption{font:12px/1.6 var(--sans);color:var(--ink-2);padding:10px 14px;margin:0}
.quadform-views .quadform-trace{aspect-ratio:auto;height:260px;min-height:260px}

/* SVD experiments share compact captions, charts, and accessible matrix entry. */
.lab .lab-caption{font:12px/1.6 var(--sans);color:var(--ink-2);padding:10px 14px;margin:0}
.svd-views .stage{aspect-ratio:auto;height:290px;min-height:290px}
.svd-cells{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1fr);gap:6px;margin-top:8px}
.svd-cells input{min-width:0;width:100%}
.chart-stage{height:260px;min-width:0}
.chart-stage canvas{display:block;width:100%;height:100%}
.approx-maps{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:8px;padding:8px}
.approx-maps canvas{display:block;width:100%;height:240px}
.matrix-values{font:11px/1.7 var(--mono);overflow-x:auto;max-width:100%}
@media(max-width:560px){.approx-maps{grid-template-columns:1fr}.approx-maps canvas{height:260px}}