/* ── Crypto Lab ─────────────────────────────────────────────────────────────
   Light "engineering manual" theme on Bootstrap 5.3: warm paper, near-black
   ink, one burnt-orange accent. The 3D view is a framed graphite display.
   Contrast (WCAG): ink 15.5, ink-2 9.0, muted 5.1 on paper; accent 5.5 on white.
   ──────────────────────────────────────────────────────────────────────────── */
:root{
  --paper:#f6f4ef; --side:#efece4; --surface:#ffffff; --surface-2:#faf8f4;
  --line:#e4dfd5; --line-strong:#d3cdc1;
  --ink:#1d1c19; --ink-2:#46433c; --muted:#6b675e;
  --accent:#b8410e; --accent-hover:#9c370c; --accent-active:#86300a;
  --accent-bright:#e8590c;            /* on dark surfaces only */
  --accent-soft:#fcf0e8;
  --ok:#2c7a4b; --danger:#b42318; --warn:#965a00; --info:#1f5fa6;
  --stage:#16171a;
  --serif:"Source Serif 4",Georgia,"Times New Roman",serif;
  --sans:"IBM Plex Sans",system-ui,-apple-system,"Segoe UI",Roboto,Arial,sans-serif;
  --mono:"IBM Plex Mono",ui-monospace,SFMono-Regular,Consolas,"Liberation Mono",monospace;
  --nav-w:272px; --panel-w:410px;

  /* Bootstrap, re-pointed at the palette above */
  --bs-body-font-family:var(--sans);
  --bs-body-font-size:.9375rem;
  --bs-body-line-height:1.6;
  --bs-body-bg:var(--paper);
  --bs-body-color:var(--ink);
  --bs-emphasis-color:var(--ink);
  --bs-secondary-color:var(--muted);
  --bs-border-color:var(--line);
  --bs-font-monospace:var(--mono);
  --bs-primary:#b8410e; --bs-primary-rgb:184,65,14;
  --bs-danger:#b42318; --bs-danger-rgb:180,35,24;
  --bs-success:#2c7a4b; --bs-success-rgb:44,122,75;
  --bs-warning:#965a00; --bs-warning-rgb:150,90,0;
  --bs-link-color:#b8410e; --bs-link-color-rgb:184,65,14;
  --bs-link-hover-color:#86300a; --bs-link-hover-color-rgb:134,48,10;
  --bs-focus-ring-color:rgba(184,65,14,.3);
  --bs-border-radius:.5rem;
  --bs-offcanvas-bg:var(--side);
}

/* ── Bootstrap component tuning ──────────────────────────────────────────── */
.btn{--bs-btn-font-weight:500;--bs-btn-border-radius:.5rem;--bs-btn-padding-y:.5rem;--bs-btn-padding-x:.9rem;--bs-btn-font-size:.9rem}
.btn-primary{
  --bs-btn-bg:#b8410e;--bs-btn-border-color:#b8410e;--bs-btn-hover-bg:#9c370c;--bs-btn-hover-border-color:#9c370c;
  --bs-btn-active-bg:#86300a;--bs-btn-active-border-color:#86300a;--bs-btn-disabled-bg:#b8410e;
  --bs-btn-disabled-border-color:#b8410e;--bs-btn-focus-shadow-rgb:184,65,14;
}
.btn-dark{
  --bs-btn-bg:#1d1c19;--bs-btn-border-color:#1d1c19;--bs-btn-hover-bg:#36332e;--bs-btn-hover-border-color:#36332e;
  --bs-btn-active-bg:#000;--bs-btn-active-border-color:#000;--bs-btn-disabled-bg:#1d1c19;
  --bs-btn-disabled-border-color:#1d1c19;--bs-btn-focus-shadow-rgb:29,28,25;
}
.btn-outline-secondary{
  --bs-btn-color:#46433c;--bs-btn-bg:#fff;--bs-btn-border-color:#d3cdc1;--bs-btn-hover-color:#1d1c19;
  --bs-btn-hover-bg:#f3f0e9;--bs-btn-hover-border-color:#bdb6a8;--bs-btn-active-color:#1d1c19;
  --bs-btn-active-bg:#e9e5dc;--bs-btn-active-border-color:#bdb6a8;--bs-btn-disabled-color:#8a857b;
  --bs-btn-disabled-bg:#fff;--bs-btn-disabled-border-color:#e4dfd5;--bs-btn-focus-shadow-rgb:70,67,60;
}
.btn-outline-danger{
  --bs-btn-color:#b42318;--bs-btn-bg:#fff;--bs-btn-border-color:#e8b9b3;--bs-btn-hover-color:#8f1c13;
  --bs-btn-hover-bg:#fdeeec;--bs-btn-hover-border-color:#b42318;--bs-btn-active-color:#fff;
  --bs-btn-active-bg:#b42318;--bs-btn-active-border-color:#b42318;--bs-btn-focus-shadow-rgb:180,35,24;
}
.btn-outline-warning{
  --bs-btn-color:#965a00;--bs-btn-bg:#fff;--bs-btn-border-color:#e3cb9c;--bs-btn-hover-color:#6f4300;
  --bs-btn-hover-bg:#fdf4e2;--bs-btn-hover-border-color:#965a00;--bs-btn-active-color:#fff;
  --bs-btn-active-bg:#965a00;--bs-btn-active-border-color:#965a00;--bs-btn-focus-shadow-rgb:150,90,0;
}
.form-control,.form-select{--bs-border-color:#d3cdc1;background-color:#fff;color:var(--ink)}
.form-control:hover,.form-select:hover{border-color:#bdb6a8}
.form-control:focus,.form-select:focus{border-color:var(--accent);box-shadow:0 0 0 .2rem rgba(184,65,14,.16)}
.form-range::-webkit-slider-thumb{background-color:var(--accent)}
.form-range::-moz-range-thumb{background-color:var(--accent)}
.form-range::-webkit-slider-thumb:active{background-color:#e9b9a0}
.form-range::-moz-range-thumb:active{background-color:#e9b9a0}
.form-range::-webkit-slider-runnable-track{background-color:#e4dfd5}
.form-range::-moz-range-track{background-color:#e4dfd5}
.form-range:focus::-webkit-slider-thumb{box-shadow:0 0 0 1px #fff,0 0 0 .25rem rgba(184,65,14,.25)}
.form-range:focus::-moz-range-thumb{box-shadow:0 0 0 1px #fff,0 0 0 .25rem rgba(184,65,14,.25)}
.text-danger{color:var(--danger)!important}
kbd{
  padding:0 .35rem;font-family:var(--mono);font-size:.75rem;line-height:1.35rem;color:var(--ink-2);
  background:var(--surface);border:1px solid var(--line-strong);border-bottom-width:2px;border-radius:.3rem;
}

/* ── Page frame ──────────────────────────────────────────────────────────── */
html,body{height:100%}
body{
  display:grid;overflow:hidden;height:100vh;height:100dvh;
  grid-template-columns:var(--nav-w) minmax(0,1fr) var(--panel-w);
  grid-template-areas:"nav main panel";
  -webkit-font-smoothing:antialiased;text-rendering:optimizeLegibility;
}
[hidden]{display:none!important}
::selection{background:#f6d2bd;color:var(--ink)}
:focus-visible{outline:2px solid var(--accent);outline-offset:2px}
button{-webkit-tap-highlight-color:transparent}

.skip{
  position:fixed;z-index:2000;top:10px;left:10px;padding:.5rem .9rem;border-radius:.5rem;
  background:var(--ink);color:#fff;font-weight:600;text-decoration:none;
  transform:translateY(-160%);transition:transform .15s ease;
}
.skip:focus{transform:none;color:#fff}

*::-webkit-scrollbar{width:10px;height:10px}
*::-webkit-scrollbar-track{background:transparent}
*::-webkit-scrollbar-thumb{background:#d6d0c4;border-radius:6px;border:2px solid transparent;background-clip:padding-box}
*::-webkit-scrollbar-thumb:hover{background-color:#bdb6a8}

/* ── Sidebar / drawer ────────────────────────────────────────────────────── */
#nav{grid-area:nav;min-height:0;--bs-offcanvas-width:min(320px,86vw)}
.nav-inner{
  display:flex;flex-direction:column;height:100%;min-height:0;background:var(--side);
  border-right:1px solid var(--line);padding-top:env(safe-area-inset-top,0px);
}
.nav-head{padding:22px 20px 16px;border-bottom:1px solid var(--line)}
.brand{display:flex;gap:12px;align-items:center}
.brand-mark{width:34px;height:34px;flex:none;color:var(--ink)}
.brand-mark .bm-lock{fill:var(--accent-bright)}
.brand-text{flex:1;min-width:0}
.brand-name{margin:0;font-family:var(--serif);font-size:1.2rem;font-weight:700;line-height:1.15;letter-spacing:-.01em}
.brand-sub{margin:2px 0 0;font-size:.8rem;color:var(--muted)}
.brand .btn-close{flex:none}

/* One segment per lesson: position and what you've opened, at a glance. */
.course-progress{display:flex;gap:3px;margin-top:18px}
.course-progress i{flex:1;height:4px;border-radius:2px;background:#dcd6ca;transition:background .3s ease}
.course-progress i.seen{background:#a39d91}
.course-progress i.cur{background:var(--accent)}
.progress-label{display:flex;justify-content:space-between;gap:8px;margin:8px 0 0;font-size:.78rem;color:var(--muted)}

#lessonList{flex:1;min-height:0;overflow-y:auto;padding:6px 12px 20px}
.act-head{display:flex;align-items:baseline;gap:8px;padding:18px 10px 6px}
.act-num{font-size:.7rem;font-weight:600;letter-spacing:.09em;text-transform:uppercase;color:var(--accent)}
.act-title{font-family:var(--serif);font-size:.98rem;font-weight:600;color:var(--ink)}
.lesson-btn{
  display:flex;gap:10px;align-items:center;width:100%;min-height:38px;text-align:left;
  padding:7px 10px;border:1px solid transparent;border-radius:.5rem;background:none;
  color:var(--ink-2);font:inherit;font-size:.875rem;line-height:1.35;cursor:pointer;
}
.lesson-btn:hover{background:rgba(29,28,25,.05);color:var(--ink)}
.lesson-btn .num{flex:0 0 20px;font-family:var(--mono);font-size:.75rem;color:var(--muted);text-align:right}
.lesson-btn .lt{flex:1;min-width:0}
.lesson-btn .tick{
  flex:none;width:15px;height:15px;opacity:0;color:var(--ok);
  fill:none;stroke:currentColor;stroke-width:2.4;stroke-linecap:round;stroke-linejoin:round;
}
.lesson-btn.seen .tick{opacity:.85}
.lesson-btn.active{
  background:var(--surface);border-color:var(--line);color:var(--ink);font-weight:600;
  box-shadow:inset 3px 0 0 var(--accent),0 1px 2px rgba(29,28,25,.06);
}
.lesson-btn.active .num{color:var(--accent);font-weight:600}
.lesson-btn.active .tick{opacity:0}
.nav-foot{padding:14px 20px calc(16px + env(safe-area-inset-bottom,0px));border-top:1px solid var(--line)}
.nav-foot p{margin:0;font-size:.75rem;color:var(--muted);line-height:1.5}
.nav-foot .keys{margin-bottom:8px}

/* ── Centre column: lesson heading + 3D display ──────────────────────────── */
#main{
  grid-area:main;display:flex;flex-direction:column;gap:16px;min-width:0;min-height:0;
  padding:24px 26px 26px;padding-top:calc(24px + env(safe-area-inset-top,0px));
}
.lesson-head{display:flex;gap:12px;align-items:flex-start;flex:none}
.lesson-head-text{min-width:0}
.kicker{margin:0 0 4px;font-size:.75rem;font-weight:600;letter-spacing:.09em;text-transform:uppercase;color:var(--accent)}
.lesson-head h1{
  margin:0;font-family:var(--serif);font-size:1.95rem;font-weight:600;line-height:1.15;
  letter-spacing:-.015em;color:var(--ink);
}
.lesson-sub{margin:6px 0 0;font-size:1rem;color:var(--ink-2);max-width:68ch}
.btn-icon{display:grid;place-items:center;width:40px;height:40px;padding:0;flex:none}
.btn-icon svg,.tool-btn svg{width:18px;height:18px;fill:none;stroke:currentColor;stroke-width:2;stroke-linecap:round;stroke-linejoin:round}

.stage-frame{
  position:relative;flex:1;min-height:0;overflow:hidden;border-radius:14px;
  background:var(--stage);border:1px solid #0d0e10;
  box-shadow:0 18px 40px -24px rgba(29,28,25,.55),0 2px 6px -2px rgba(29,28,25,.18);
}
#stage{position:absolute;inset:0}
.stage-tools{position:absolute;top:14px;right:14px;display:flex;gap:8px}
.tool-btn{
  display:flex;align-items:center;gap:7px;height:34px;padding:0 12px 0 10px;border-radius:.5rem;
  border:1px solid rgba(255,255,255,.16);background:rgba(22,23,26,.82);color:#ebe9e4;
  font:inherit;font-size:.82rem;cursor:pointer;animation:fade .25s ease;
}
.tool-btn:hover{background:rgba(40,41,46,.92);border-color:rgba(255,255,255,.28)}
.tool-btn:focus-visible{outline-color:var(--accent-bright)}
@keyframes fade{from{opacity:0}}
#stageHint{
  position:absolute;bottom:12px;left:50%;transform:translateX(-50%);white-space:nowrap;pointer-events:none;
  padding:4px 12px;border-radius:999px;background:rgba(22,23,26,.72);
  font-size:.78rem;color:#a19e96;transition:opacity .6s ease;
}
#stageHint.done{opacity:0}

/* ── Lesson panel ────────────────────────────────────────────────────────── */
#panel{
  grid-area:panel;display:flex;flex-direction:column;min-width:0;min-height:0;
  background:var(--surface);border-left:1px solid var(--line);
  padding-top:env(safe-area-inset-top,0px);
}
.panel-tabs{
  flex:none;padding:0 22px;border-bottom:1px solid var(--line);
  --bs-nav-underline-gap:1.5rem;--bs-nav-link-padding-y:.95rem;--bs-nav-link-font-weight:500;
  --bs-nav-link-color:var(--muted);--bs-nav-link-hover-color:var(--ink);--bs-nav-underline-border-width:2px;
}
.panel-tabs .nav-link{font-size:.9rem;margin-bottom:-1px}
.panel-tabs .nav-link.active{color:var(--ink);font-weight:600;border-bottom-color:var(--accent)}
.panel-tabs .nav-link:focus-visible{outline-offset:-2px;box-shadow:none}
/* Shown on Controls until it is opened once per lesson. */
.tab-dot{
  display:none;width:6px;height:6px;margin-left:5px;border-radius:50%;background:var(--accent);
  vertical-align:top;position:relative;top:3px;animation:ping 1.8s ease-out 3;
}
.nav-link.unseen .tab-dot{display:inline-block}
@keyframes ping{0%{box-shadow:0 0 0 0 rgba(184,65,14,.5)}80%,100%{box-shadow:0 0 0 7px rgba(184,65,14,0)}}

.panel-body{flex:1;min-height:0;overflow-y:auto}
.tab-pane{padding:24px 26px 34px}
.tab-pane:focus-visible{outline-offset:-3px}

.panel-foot{
  flex:none;display:flex;gap:10px;padding:12px 18px calc(14px + env(safe-area-inset-bottom,0px));
  border-top:1px solid var(--line);background:var(--surface);
}
.navbtn{
  flex:1 1 0;min-width:0;display:flex;flex-direction:column;align-items:flex-start;gap:0;
  padding:.5rem .9rem;text-align:left;border-radius:.6rem;
}
.navbtn-next{flex-grow:1.6;align-items:flex-end;text-align:right}
.navbtn .nb-k{font-size:.75rem;font-weight:500;opacity:.85}
.navbtn .nb-t{max-width:100%;font-size:.9rem;font-weight:600;line-height:1.35;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}

/* ── Reading (Learn) ─────────────────────────────────────────────────────── */
.tab-pane h3{
  margin:30px 0 10px;font-family:var(--serif);font-size:1.2rem;font-weight:600;line-height:1.3;
  letter-spacing:-.005em;color:var(--ink);
}
.tab-pane h3:first-child,.tab-pane .lead + h3{margin-top:0}
.tab-pane p,.tab-pane ul,.tab-pane ol{font-size:.95rem;line-height:1.68;color:var(--ink-2)}
.tab-pane p{margin:0 0 14px}
.tab-pane ul,.tab-pane ol{margin:0 0 16px;padding-left:1.3rem}
.tab-pane li{margin-bottom:7px;padding-left:2px}
.tab-pane li::marker{color:var(--muted)}
.tab-pane strong{color:var(--ink);font-weight:600}
.tab-pane em{color:var(--ink)}
.tab-pane code{
  font-family:var(--mono);font-size:.82rem;color:#8f320b;background:#f4f0e8;
  border:1px solid #e9e3d8;padding:1px 5px;border-radius:4px;overflow-wrap:anywhere;
}
.tab-pane .lead{display:none;margin-bottom:20px;font-family:var(--serif);font-size:1.08rem;line-height:1.5;color:var(--ink)}

.callout{
  margin:0 0 18px;padding:12px 15px;border:1px solid #ecd9ae;border-left:3px solid #b7791f;
  border-radius:.5rem;background:#fdf8ec;
}
.callout p{margin:0;font-size:.9rem;line-height:1.6;color:#4d3a12}
.callout.cy{background:var(--accent-soft);border-color:#f2d6c4;border-left-color:var(--accent)}
.callout.cy p{color:#4a2410}
.callout.rd{background:#fdefed;border-color:#f2c9c4;border-left-color:var(--danger)}
.callout.rd p{color:#5c140e}
.callout strong{color:inherit}

.kv{width:100%;margin:0 0 18px;border-collapse:collapse;font-size:.88rem;border-top:1px solid var(--line)}
.kv td{padding:8px 12px 8px 0;border-bottom:1px solid var(--line);vertical-align:top;color:var(--ink-2);line-height:1.5}
.kv td:first-child{width:1%;white-space:nowrap;color:var(--ink);font-weight:600}
.kv td:last-child{padding-right:0}

.goto{
  padding:0;border:0;background:none;font:inherit;font-weight:600;color:var(--accent);cursor:pointer;
  text-decoration:underline;text-decoration-color:rgba(184,65,14,.4);text-underline-offset:3px;
}
.goto:hover{color:var(--accent-hover);text-decoration-color:currentColor}
.learn-cta{
  display:flex;align-items:center;justify-content:space-between;gap:14px;margin-top:28px;
  padding:16px 18px;border:1px solid var(--line);border-radius:.75rem;background:var(--surface-2);
}
.learn-cta p{margin:0;font-family:var(--serif);font-size:1.02rem;color:var(--ink)}
.learn-cta .btn{flex:none;white-space:nowrap}

/* ── Controls (built by ui.js) ───────────────────────────────────────────── */
.ctl-section{margin-bottom:28px}
.ctl-section > h4{
  margin:0 0 14px;padding-bottom:8px;border-bottom:1px solid var(--line);
  font-family:var(--sans);font-size:.72rem;font-weight:600;letter-spacing:.09em;text-transform:uppercase;color:var(--muted);
}
.ctl{margin-bottom:14px}
.ctl label,.ctl-section > label{display:block;margin-bottom:6px;font-size:.85rem;font-weight:500;color:var(--ink)}
.hint{font-size:.8rem;font-weight:400;color:var(--muted)}
.ctl input[type=text],.ctl textarea{font-family:var(--mono);font-size:.875rem}
.ctl textarea{resize:vertical;min-height:64px;line-height:1.5}
.ctl input.bad{border-color:var(--danger);box-shadow:0 0 0 .2rem rgba(180,35,24,.12)}
.ctl .rowline{display:flex;justify-content:space-between;align-items:baseline;gap:10px;margin-bottom:2px;font-size:.85rem;font-weight:500;color:var(--ink)}
.ctl .rowline b{font-family:var(--mono);font-size:.85rem;font-weight:600;color:var(--accent)}
.ctl-btn{margin-bottom:8px}
.btnrow{display:flex;gap:8px}
.btnrow .btn{flex:1 1 0;min-width:0}
.chips{display:flex;flex-wrap:wrap;gap:6px;margin-bottom:12px}
.chip{
  min-height:34px;padding:5px 14px;border:1px solid var(--line-strong);border-radius:999px;
  background:var(--surface);color:var(--ink-2);font:inherit;font-size:.85rem;font-weight:500;cursor:pointer;
  transition:background .12s ease,border-color .12s ease,color .12s ease;
}
.chip:hover{border-color:#a8a196;color:var(--ink)}
.chip.on{background:var(--ink);border-color:var(--ink);color:#fff}

.readout{margin-bottom:10px;padding:10px 12px;background:var(--surface-2);border:1px solid var(--line);border-radius:.5rem}
.readout .rl{margin-bottom:4px;font-size:.7rem;font-weight:600;letter-spacing:.07em;text-transform:uppercase;color:var(--muted)}
.readout .rv{
  font-family:var(--mono);font-size:.85rem;line-height:1.55;color:var(--ink);word-break:break-all;
  white-space:pre-line;   /* several readouts are multi-line ("\n"-separated) */
}
.readout .rv.big{font-size:1.2rem;font-weight:500;letter-spacing:.08em}
.readout .rv.ok{color:var(--ok)} .readout .rv.err{color:var(--danger)} .readout .rv.am{color:var(--warn)}

.logbox{
  max-height:210px;overflow-y:auto;padding:8px 10px;background:var(--surface-2);border:1px solid var(--line);
  border-radius:.5rem;font-family:var(--mono);font-size:.78rem;line-height:1.65;color:var(--ink-2);
}
.logbox div{padding:1px 0;border-bottom:1px solid #eee9e0}
.logbox div:last-child{border-bottom:0}
.logbox .t{margin-right:8px;color:var(--muted)}
.logbox .ok{color:var(--ok)} .logbox .err{color:var(--danger)}
.logbox .am{color:var(--warn)} .logbox .cy{color:var(--info)}

.data-intro{font-size:.875rem!important;color:var(--muted)!important;margin-bottom:12px!important}
#dataOut{
  margin:0;padding:12px 14px;background:var(--surface-2);border:1px solid var(--line);border-radius:.5rem;
  font-family:var(--mono);font-size:.8rem;line-height:1.75;color:var(--ink-2);white-space:pre-wrap;word-break:break-all;
}
#dataOut b{color:var(--ink);font-weight:600}

.bits{display:flex;flex-wrap:wrap;gap:2px;margin-bottom:12px}
.bits i{
  display:grid;place-items:center;width:13px;height:17px;border-radius:2px;background:#ebe6dc;
  font-family:var(--mono);font-size:9.5px;font-style:normal;color:#8a8478;transition:.18s;
}
.bits i.one{background:#33302b;color:#f6f4ef}
.bits i.flip{background:var(--danger);color:#fff}

/* ── Boot overlay ────────────────────────────────────────────────────────── */
#boot{position:fixed;inset:0;z-index:3000;display:grid;place-items:center;background:var(--paper);transition:opacity .4s ease}
#boot.gone{opacity:0;pointer-events:none}
.boot-inner{max-width:400px;padding:24px;text-align:center}
.boot-inner .spinner-border{width:2rem;height:2rem;margin-bottom:18px;color:var(--accent);border-width:.18em}
#bootMsg{margin:0;font-family:var(--serif);font-size:1.1rem;color:var(--ink)}
.boot-hint{margin:12px 0 0;font-size:.82rem;line-height:1.6;color:var(--muted)}
.boot-hint code{color:#8f320b}

/* ── Responsive ──────────────────────────────────────────────────────────── */
@media (max-width:1279.98px){
  :root{--nav-w:248px;--panel-w:372px}
  #main{padding:20px 20px 22px}
  .lesson-head h1{font-size:1.65rem}
}
/* Below Bootstrap's lg breakpoint the sidebar becomes an offcanvas drawer. */
@media (max-width:991.98px){
  body{grid-template-columns:minmax(0,1fr);grid-template-rows:auto minmax(0,1fr);grid-template-areas:"main" "panel"}
  .nav-inner{border-right:0}
  #main{gap:10px;padding:12px 12px 12px;padding-top:calc(12px + env(safe-area-inset-top,0px))}
  .lesson-head{align-items:center}
  .lesson-head h1{font-size:1.3rem}
  .kicker{font-size:.68rem;margin-bottom:2px}
  .lesson-sub{display:none}
  .tab-pane .lead{display:block}
  .stage-frame{flex:none;height:clamp(230px,38dvh,440px);border-radius:12px}
  .stage-tools{top:10px;right:10px}
  .tool-btn{width:38px;height:38px;padding:0;justify-content:center}
  .tool-btn span{display:none}
  #panel{border-left:0;border-top:1px solid var(--line);padding-top:0}
}
@media (max-width:575.98px){
  .tab-pane{padding:20px 16px 28px}
  .panel-tabs{padding:0 16px}
  .panel-foot{padding-left:12px;padding-right:12px}
  .lesson-head h1{font-size:1.15rem}
  .learn-cta{flex-direction:column;align-items:stretch}
}
@media (pointer:coarse){
  .lesson-btn{min-height:44px}
  .chip{min-height:40px;padding:7px 16px}
  .ctl-btn,.btnrow .btn{min-height:44px}
}
/* `transition:none`, not the common `transition-duration:.01ms` trick: that one leaves
   transition-property at its default `all`, so inherited `visibility` steps down the
   tree a frame per level — the drawer's buttons stayed hidden (and unfocusable) on open. */
@media (prefers-reduced-motion:reduce){
  *,*::before,*::after{transition:none!important;scroll-behavior:auto!important}
  .tab-dot,.tool-btn{animation:none}
}