:root{
  --bg:#fff;--fg:#1a1d21;--muted:#5c6570;--line:#e3e7ec;--surf:#f5f7fa;--surf2:#eef2f6;
  --brand:#0056d2;--brand-d:#00419e;--brand-s:#e8f1fc;--ok:#0f7b3a;--ok-bg:#e6f6ec;--bad:#9b1c1c;--bad-bg:#fdecea;
  --hero:#0b1f3a;--hero-fg:#fff;--hero-muted:#c9d6e8;--shadow:0 4px 18px rgba(15,42,68,.08);--radius:12px;
  --focus:#0056d2;--max:1180px;--prose:68ch;
}
html.dark{
  --bg:#0f1419;--fg:#e8eaed;--muted:#9aa3ad;--line:#2a323c;--surf:#1a222c;--surf2:#222b36;
  --brand:#6ba3ff;--brand-d:#9bc0ff;--brand-s:#1a2a44;--ok:#5ddea0;--ok-bg:#143226;--bad:#ff8a8a;--bad-bg:#3a1a1a;
  --hero:#071222;--hero-fg:#fff;--hero-muted:#a8b8cc;--shadow:0 4px 18px rgba(0,0,0,.35);--focus:#6ba3ff;
}
@media(prefers-color-scheme:dark){
  html:not(.light):not(.hc){
    --bg:#0f1419;--fg:#e8eaed;--muted:#9aa3ad;--line:#2a323c;--surf:#1a222c;--surf2:#222b36;
    --brand:#6ba3ff;--brand-d:#9bc0ff;--brand-s:#1a2a44;--ok:#5ddea0;--ok-bg:#143226;--bad:#ff8a8a;--bad-bg:#3a1a1a;
    --hero:#071222;--hero-fg:#fff;--hero-muted:#a8b8cc;--shadow:0 4px 18px rgba(0,0,0,.35);--focus:#6ba3ff;
  }
}
*{box-sizing:border-box}
html{font-size:100%;-webkit-text-size-adjust:100%}
body{margin:0;font:1rem/1.65 Inter,system-ui,-apple-system,"Segoe UI",sans-serif;color:var(--fg);background:var(--bg);-webkit-font-smoothing:antialiased}
a{color:var(--brand);text-underline-offset:2px}a:hover{color:var(--brand-d)}
img,svg{max-width:100%;height:auto}
h1,h2,h3,.h3{line-height:1.25;font-weight:700;letter-spacing:-.015em;margin:0 0 .75rem;color:var(--fg)}
h1{font-size:clamp(1.75rem,3vw,2.5rem)}h2{font-size:1.375rem;margin-top:2rem}h3,.h3{font-size:1.0625rem;margin:.75rem 0 .35rem}
p{margin:0 0 1rem}.wrap{max-width:var(--max);margin:0 auto;padding:0 1.25rem}.mut,.meta{color:var(--muted)}.meta{font-size:.875rem;margin:.25rem 0}
.sr{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap}
:focus-visible{outline:3px solid var(--focus);outline-offset:2px;border-radius:4px}
.hero :focus-visible,.dark-band :focus-visible{outline-color:#ffd166}main:focus{outline:none}
.skip{position:absolute;left:-999px;top:.5rem;background:var(--brand);color:#fff;padding:.75rem 1rem;z-index:40;border-radius:8px}.skip:focus{left:1rem}

/* header */
.hd{background:var(--bg);border-bottom:1px solid var(--line);position:sticky;top:0;z-index:30;box-shadow:0 1px 0 rgba(0,0,0,.03)}
.hdi{display:flex;align-items:center;gap:1rem;min-height:64px}
.logo{font-weight:700;font-size:1.05rem;color:var(--fg);text-decoration:none;display:flex;align-items:center;gap:.55rem;min-height:44px;white-space:nowrap}
.lm{background:var(--brand);color:#fff;font-size:.7rem;letter-spacing:.04em;width:34px;height:34px;display:grid;place-items:center;border-radius:8px;font-weight:700}
.nv ul{list-style:none;display:flex;gap:.1rem;margin:0;padding:0}
.nv a{display:flex;align-items:center;height:44px;padding:0 .65rem;color:var(--fg);text-decoration:none;font-weight:500;font-size:.9rem;border-radius:8px;white-space:nowrap}
.nv a:hover{background:var(--surf)}.nv a[aria-current]{color:var(--brand);background:var(--brand-s);font-weight:600}
.srch{flex:1;display:flex;align-items:center;position:relative;max-width:360px;margin-left:auto}
.srch input{width:100%;height:42px;padding:0 5.5rem 0 1rem;border:1px solid var(--line);border-radius:999px;font:inherit;font-size:.9rem;background:var(--surf);color:var(--fg)}
.srch input:focus{background:var(--bg);border-color:var(--brand)}.sbtn{position:absolute;right:3px;height:36px;padding:0 .9rem;border-radius:999px;border:0;background:var(--brand);color:#fff;font:inherit;font-size:.85rem;font-weight:600;cursor:pointer}
.sbtn:hover{background:var(--brand-d)}
.a11y{position:relative}.a11y summary{list-style:none;display:flex;align-items:center;height:42px;padding:0 .75rem;border:1px solid var(--line);border-radius:8px;font-size:.85rem;font-weight:500;cursor:pointer;white-space:nowrap;color:var(--fg)}
.a11y summary::-webkit-details-marker{display:none}
.a11y .tools{position:absolute;right:0;top:50px;background:var(--bg);border:1px solid var(--line);border-radius:10px;box-shadow:var(--shadow);padding:.5rem;display:flex;flex-wrap:wrap;gap:.25rem;min-width:200px;z-index:40}
.tb-btn,.menu-btn{min-height:44px;min-width:44px;padding:0 .75rem;border:1px solid var(--line);background:var(--bg);border-radius:8px;font:inherit;font-size:.85rem;font-weight:500;cursor:pointer;color:var(--fg)}
.tb-btn:hover,.menu-btn:hover{background:var(--surf)}.tb-btn[aria-pressed=true]{background:var(--fg);color:var(--bg);border-color:var(--fg)}.menu-btn{display:none}

.btn{display:inline-flex;align-items:center;justify-content:center;gap:.5rem;min-height:44px;padding:.65rem 1.2rem;border-radius:8px;font:inherit;font-size:.9375rem;font-weight:600;border:1px solid var(--brand);text-decoration:none;cursor:pointer;line-height:1.3;text-align:center}
.pri{background:var(--brand);color:#fff}.pri:hover{background:var(--brand-d);color:#fff}.out{color:var(--brand);background:transparent}.out:hover{background:var(--brand-s)}
.ghost{border-color:rgba(255,255,255,.75);color:#fff;background:transparent}.ghost:hover{background:rgba(255,255,255,.12);color:#fff}
.lg{padding:.85rem 1.4rem}.full{display:flex;width:100%;margin-top:.5rem}

/* hero Coursera-like */
.hero{position:relative;background:var(--hero);color:var(--hero-fg);overflow:hidden;min-height:320px}
.hero-bg{position:absolute;inset:0;opacity:.35;object-fit:cover;width:100%;height:100%;pointer-events:none;content-visibility:auto}
.hero-scrim{position:absolute;inset:0;background:linear-gradient(105deg,rgba(7,18,34,.95) 0%,rgba(7,18,34,.82) 48%,rgba(7,18,34,.45) 100%)}
.hero .wrap{position:relative;z-index:1;padding:3.5rem 1.25rem 3.25rem;display:grid;grid-template-columns:minmax(0,1.15fr) minmax(0,.85fr);gap:2.5rem;align-items:center}
.hero h1{color:#fff;max-width:18ch}.hero .lead{color:var(--hero-muted);font-size:1.1rem;max-width:40ch}
.eyebrow{text-transform:uppercase;font-size:.72rem;font-weight:700;letter-spacing:.12em;color:var(--hero-muted);margin:0 0 .75rem}
.hero-card{background:rgba(255,255,255,.08);border:1px solid rgba(255,255,255,.18);border-radius:var(--radius);padding:1.25rem;backdrop-filter:blur(6px)}
.hero-card h2{color:#fff;font-size:1.05rem;margin:0 0 .75rem}.hero-card ul{margin:0;padding:0;list-style:none}
.hero-card li{padding:.45rem 0 .45rem 1.6rem;position:relative;color:var(--hero-muted);font-size:.95rem;border-bottom:1px solid rgba(255,255,255,.08)}
.hero-card li:last-child{border:0}.hero-card li:before{content:"";position:absolute;left:.25rem;top:.7em;width:.45rem;height:.7rem;border:solid #7dd3a0;border-width:0 2px 2px 0;transform:rotate(45deg)}
.continue{margin-top:1.25rem;padding:1rem 1.1rem;background:rgba(0,86,210,.25);border:1px solid rgba(107,163,255,.45);border-radius:10px}
.continue[hidden]{display:none}.continue p{margin:0 0 .65rem;color:#fff;font-weight:600}

.stats{list-style:none;padding:0;margin:-1.75rem auto 0;max-width:var(--max);display:grid;grid-template-columns:repeat(4,1fr);gap:1rem;position:relative;z-index:2;padding-left:1.25rem;padding-right:1.25rem}
.stats li{background:var(--bg);border:1px solid var(--line);border-radius:var(--radius);padding:1.1rem 1.2rem;box-shadow:var(--shadow)}
.stats b{display:block;font-size:1.55rem;line-height:1.15}.stats span{color:var(--muted);font-size:.85rem}

.sec{padding:2.75rem 1.25rem}.sh{display:flex;justify-content:space-between;align-items:baseline;flex-wrap:wrap;gap:1rem;margin-bottom:1.25rem}.sh h2{margin:0}
.row{display:flex;gap:.75rem;flex-wrap:wrap;margin-top:1.5rem}
.outcomes{background:var(--surf);border-top:1px solid var(--line);border-bottom:1px solid var(--line)}
.out-grid{list-style:none;margin:0;padding:0;display:grid;grid-template-columns:repeat(3,1fr);gap:1rem}
.out-grid li{background:var(--bg);border:1px solid var(--line);border-radius:var(--radius);padding:1.15rem 1.25rem;box-shadow:var(--shadow)}
.out-grid strong{display:block;margin-bottom:.35rem;color:var(--brand)}

/* cards */
.grid{list-style:none;padding:0;margin:0;display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:1.25rem}.g3{grid-template-columns:repeat(3,minmax(0,1fr))}
.card{border:1px solid var(--line);border-radius:var(--radius);overflow:hidden;box-shadow:var(--shadow);background:var(--bg);display:flex;flex-direction:column;transition:transform .15s,box-shadow .15s}
.card:hover{transform:translateY(-2px);box-shadow:0 10px 28px rgba(15,42,68,.12)}
.cl{display:flex;flex-direction:column;color:var(--fg);text-decoration:none;height:100%}.cl:hover h3{color:var(--brand)}
.thw{position:relative;flex:none;background:var(--surf2)}.thw img.th,.th{display:block;width:100%;aspect-ratio:16/9;object-fit:cover;height:auto}
.thw span{position:absolute;left:12px;bottom:10px;background:rgba(0,0,0,.55);color:#fff;font-weight:700;font-size:.95rem;padding:.2rem .55rem;border-radius:6px}
.cb{padding:1rem 1.1rem 1.2rem;display:flex;flex-direction:column;flex:1}.cb h3{margin-top:.5rem}.badge{align-self:flex-start;font-size:.72rem;font-weight:700;background:var(--brand-s);color:var(--brand);padding:.2rem .5rem;border-radius:4px;letter-spacing:.02em}
.card .prog-row{margin-top:auto;padding-top:.85rem;border-top:1px solid var(--line)}
.prog{font-size:.8rem;font-weight:600;margin:0 0 .35rem;color:var(--muted)}
.pbar{height:6px;background:var(--surf2);border-radius:99px;overflow:hidden}.pbar>i{display:block;height:100%;width:0;background:var(--brand);border-radius:99px;transition:width .3s}

/* lesson cover */
.lcover{position:relative;background:var(--hero);color:#fff;border-radius:0 0 var(--radius) var(--radius);overflow:hidden;margin:0 0 1.25rem}
.lcover img{position:absolute;inset:0;width:100%;height:100%;object-fit:cover;opacity:.4}
.lcover .inner{position:relative;padding:1.75rem 1.5rem;background:linear-gradient(180deg,rgba(7,18,34,.55),rgba(7,18,34,.88))}
.lcover h1{color:#fff;margin:0 0 .5rem}.lcover .meta{color:var(--hero-muted)}
.lcover .bc ol{color:var(--hero-muted)}.lcover .bc a{color:#fff}

.dark-band{background:var(--hero);color:#fff;padding:2.25rem 0 2.5rem}.dark-band h1{color:#fff}.dark-band a{color:#fff}.lt{color:var(--hero-muted)}
.dk{display:grid;grid-template-columns:minmax(0,1fr) 300px;gap:2rem;align-items:start}
.float{background:var(--bg);color:var(--fg);border-radius:var(--radius);box-shadow:var(--shadow);overflow:hidden}
.float .cb{padding:1.25rem}.bar{height:8px;background:var(--surf2);border-radius:4px;margin:.5rem 0 1rem}.bar i{display:block;height:100%;width:0;background:var(--brand);border-radius:4px}

.mcol{padding:2rem 1.25rem}.mcol>*{max-width:calc(100% - 340px)}
.box{border:1px solid var(--line);border-radius:var(--radius);padding:1.25rem 1.4rem;margin-bottom:1.25rem;background:var(--bg);box-shadow:var(--shadow)}
.box h2{margin-top:0;font-size:1.15rem}
.ex{border-left:3px solid var(--brand);background:var(--surf);padding:.9rem 1.1rem;margin:1rem 0;border-radius:0 10px 10px 0;font-size:.95rem}
.ex strong{display:block;margin-bottom:.25rem;color:var(--brand);font-size:.8rem;text-transform:uppercase;letter-spacing:.06em}
.chk{list-style:none;padding:0;margin:0;display:grid;grid-template-columns:1fr 1fr;gap:.45rem 1.5rem}
.chk li{padding-left:1.6rem;position:relative}.chk li:before{content:"";position:absolute;left:.3rem;top:.35em;width:.4rem;height:.75rem;border:solid var(--brand);border-width:0 2px 2px 0;transform:rotate(45deg)}
.acc{border:1px solid var(--line);border-radius:var(--radius);overflow:hidden}
.acc details+details{border-top:1px solid var(--line)}
.acc summary{display:flex;justify-content:space-between;align-items:center;gap:1rem;padding:1rem 1.15rem;min-height:52px;cursor:pointer;background:var(--surf);font-weight:600;list-style:none}
.acc summary::-webkit-details-marker{display:none}.acc summary:hover{background:var(--surf2)}.dp{padding:1rem 1.15rem 1.15rem 1.15rem;font-size:.95rem}

.tmg{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:1.25rem;margin-top:1.25rem}
.tm{border:1px solid var(--line);border-radius:var(--radius);padding:1.25rem;background:var(--bg);box-shadow:var(--shadow)}
.tm h2{font-size:1.05rem;margin:0 0 .75rem}.tm h2 a{color:var(--fg);text-decoration:none;display:inline-flex;min-height:44px;align-items:center}.tm h2 a:hover{color:var(--brand)}
.tm ol{margin:0;padding-left:1.2rem}.tm li{padding:.35rem 0;border-bottom:1px solid var(--line)}.tm li:last-child{border:0}
.bc ol{list-style:none;padding:0;margin:0 0 .85rem;display:flex;flex-wrap:wrap;font-size:.85rem;color:var(--muted)}.bc li+li:before{content:"/";padding:0 .45rem;opacity:.7}

/* lesson layout */
.les{display:grid;grid-template-columns:250px minmax(0,1fr) 200px;gap:2rem;padding:1.75rem 1.25rem 5rem;align-items:start}
.lside,.toc{position:sticky;top:84px}
.lside{border:1px solid var(--line);border-radius:var(--radius);padding:.85rem;font-size:.88rem;background:var(--bg);box-shadow:var(--shadow)}
.lside .meta{font-weight:600;margin:0 0 .4rem;padding:0 .4rem}.lside .meta a{color:var(--fg);text-decoration:none}
.lside ol{list-style:none;padding:0;margin:0}
.lside a{display:block;padding:.5rem .55rem;color:var(--fg);border-radius:6px;text-decoration:none;line-height:1.35}
.lside a:hover{background:var(--surf)}.lside a[aria-current]{background:var(--brand-s);color:var(--brand);font-weight:600;box-shadow:inset 3px 0 0 var(--brand)}
.lside .parts-mini{margin:.35rem 0 .5rem .75rem;padding:0;list-style:none}
.lside .parts-mini a{font-size:.8rem;padding:.35rem .5rem;min-height:36px;display:flex;align-items:center;color:var(--muted)}
.lside .parts-mini a[aria-current]{color:var(--brand);font-weight:600;background:var(--brand-s)}
.lbody{max-width:var(--prose);min-width:0;font-size:1.05rem}.lbody h2{scroll-margin-top:96px}
.toc{border-left:2px solid var(--line);padding:0 0 0 .9rem;font-size:.85rem}
.toc-h{font-size:.72rem;text-transform:uppercase;letter-spacing:.08em;color:var(--muted);margin:0 0 .4rem}
.toc ol{list-style:none;padding:0;margin:0}.toc a{display:block;padding:.28rem 0;color:var(--muted);text-decoration:none}.toc a:hover{color:var(--brand)}

.note{border-left:3px solid var(--brand);background:var(--surf);padding:.85rem 1.05rem;margin:1.1rem 0;font-size:.92rem;border-radius:0 10px 10px 0}.note p{margin:0}
.parts{display:flex;flex-wrap:wrap;align-items:center;gap:.65rem 1rem;margin:1rem 0;padding:1rem;background:var(--surf);border:1px solid var(--line);border-radius:var(--radius)}
.part-lab{margin:0;font-size:.92rem}.pills{display:flex;flex-wrap:wrap;gap:.4rem}
.pill{display:inline-flex;align-items:center;justify-content:center;min-height:40px;min-width:40px;padding:.4rem .8rem;border-radius:999px;border:1px solid var(--line);background:var(--bg);color:var(--fg);text-decoration:none;font-size:.85rem;font-weight:500}
.pill:hover{background:var(--brand-s);border-color:var(--brand);color:var(--brand)}
.pill.on,.pill[aria-current=page]{background:var(--brand);border-color:var(--brand);color:#fff;font-weight:600}

.keybox{border:1px solid var(--line);border-radius:var(--radius);padding:1.2rem 1.35rem;margin:2rem 0 1.25rem;background:linear-gradient(180deg,var(--brand-s),var(--bg));box-shadow:var(--shadow)}
.keybox h2{margin:0 0 .75rem;font-size:1.15rem}.keybox ul{margin:0;padding-left:1.2rem}.keybox li{margin:.35rem 0}
.miniq{border:1px solid var(--line);border-radius:var(--radius);padding:1.2rem 1.35rem;margin:0 0 1.5rem;background:var(--bg);box-shadow:var(--shadow)}
.miniq h2{margin:0 0 .5rem;font-size:1.15rem}.miniq .hint{margin:0 0 1rem;color:var(--muted);font-size:.9rem}
.miniq fieldset{border:1px solid var(--line);border-radius:10px;padding:1rem 1.1rem;margin:0 0 .9rem}
.miniq legend{font-weight:600;padding:0 .35rem}
.done{margin:1.5rem 0;padding:1.15rem;border:1px solid var(--line);border-radius:var(--radius);display:flex;align-items:center;gap:1rem;background:var(--surf)}
.pn{display:flex;justify-content:space-between;gap:.75rem;flex-wrap:wrap;border-top:1px solid var(--line);padding-top:1.25rem;margin-top:1.25rem}.pn .btn{max-width:48%}

/* sticky mobile bottom nav */
.mob-nav{display:none;position:fixed;left:0;right:0;bottom:0;z-index:25;background:var(--bg);border-top:1px solid var(--line);padding:.55rem .75rem calc(.55rem + env(safe-area-inset-bottom));box-shadow:0 -6px 20px rgba(0,0,0,.08);gap:.5rem}
.mob-nav .btn{flex:1;font-size:.85rem;padding:.55rem .6rem}

.fig{margin:1.35rem 0}.fig img{display:block;width:100%;border-radius:10px;border:1px solid var(--line);background:var(--surf)}
.fig figcaption{font-size:.85rem;color:var(--muted);margin-top:.45rem;line-height:1.45}.fig .cred{display:block;font-size:.8rem;margin-top:.2rem}
.fig-mod{max-width:420px}.fig-author{max-width:260px}

.narrow{max-width:820px}fieldset.q{border:1px solid var(--line);border-radius:10px;padding:1.15rem 1.3rem;margin:0 0 1.1rem}legend{font-weight:600;padding:0 .35rem}
.opt{display:flex;align-items:center;gap:.7rem;min-height:44px;padding:0 .7rem;border-radius:8px;margin:.2rem 0}.opt:hover{background:var(--surf)}.opt input{width:18px;height:18px;accent-color:var(--brand);flex:none}.opt label{flex:1;cursor:pointer;padding:.45rem 0}
.fb{padding:.7rem .95rem;border-radius:8px;margin-top:.45rem}.fb.ok{background:var(--ok-bg);color:var(--ok)}.fb.ko{background:var(--bad-bg);color:var(--bad)}.err{color:var(--bad);font-weight:600}
label{font-weight:500}.inp{flex:1;min-height:44px;padding:0 1rem;border:1px solid var(--line);border-radius:8px;font:inherit;background:var(--bg);color:var(--fg)}
.sres{padding-left:1.2rem}.sres li{margin-bottom:1.1rem}.sres a{font-weight:600}

/* progress dashboard */
.dash{display:grid;gap:1rem}.dash-mod{border:1px solid var(--line);border-radius:var(--radius);padding:1.15rem 1.25rem;background:var(--bg);box-shadow:var(--shadow)}
.dash-mod h2{margin:0 0 .5rem;font-size:1.05rem}.dash-mod .meta{margin-bottom:.5rem}
.glos-nav{display:flex;flex-wrap:wrap;gap:.4rem;margin:1rem 0 1.5rem}
.glos-nav a{display:inline-flex;align-items:center;min-height:40px;padding:.35rem .7rem;border-radius:999px;background:var(--surf);border:1px solid var(--line);text-decoration:none;color:var(--fg);font-size:.85rem}
.glos-nav a:hover{background:var(--brand-s);color:var(--brand)}
.term{border-top:1px solid var(--line);padding:1.25rem 0;scroll-margin-top:96px}.term h2{font-size:1.2rem;margin:0 0 .5rem}
.term-link{font-weight:600;text-decoration:underline;text-decoration-thickness:1px;text-underline-offset:2px}

.ft{border-top:1px solid var(--line);margin-top:3rem;padding:2rem 0 5.5rem;font-size:.875rem;color:var(--muted);background:var(--surf)}.ft p{margin:0 0 .5rem;max-width:80ch}
.table-wrap{overflow-x:auto;border:1px solid var(--line);border-radius:var(--radius)}
.cred-table{width:100%;border-collapse:collapse;font-size:.85rem}.cred-table th,.cred-table td{padding:.7rem .9rem;border-bottom:1px solid var(--line);text-align:left;vertical-align:middle}
.cred-table th{background:var(--surf);font-weight:600}.cred-th{object-fit:cover;border-radius:4px;border:1px solid var(--line)}

.hc body,.hc{--fg:#000;--bg:#fff;--muted:#000;--line:#000;--surf:#fff;--brand:#00337a;--brand-s:#e6eeff}
.hc a{text-decoration:underline}
@media(prefers-reduced-motion:reduce){*{transition:none!important;animation:none!important;scroll-behavior:auto!important}}

@media(max-width:1180px){.les{grid-template-columns:220px minmax(0,1fr)}.toc{display:none}.nv a{padding:0 .45rem}}
@media(max-width:1024px){.grid{grid-template-columns:repeat(3,minmax(0,1fr))}.hero .wrap{grid-template-columns:1fr}.out-grid{grid-template-columns:1fr 1fr}}
@media(max-width:960px){
  .hdi{flex-wrap:wrap;height:auto;padding:.7rem 0;gap:.6rem}
  .js .menu-btn{display:block;margin-left:auto}.srch{order:4;flex-basis:100%;max-width:none;margin:0}
  .js .nv{display:none;order:5;flex-basis:100%}.js .nv.open{display:block}.nv ul{flex-direction:column}.nv a{height:48px}
  .a11y{order:3}.grid,.g3{grid-template-columns:repeat(2,minmax(0,1fr))}
  .dk,.les,.tmg{grid-template-columns:1fr}.mcol>*{max-width:none}.lside{position:static;order:2}.lbody{order:1}
  .stats{grid-template-columns:repeat(2,1fr)}.mob-nav{display:flex}.pn{display:none}
  .notoc{grid-template-columns:1fr}
}
@media(max-width:600px){
  .grid,.g3,.out-grid{grid-template-columns:1fr}.chk{grid-template-columns:1fr}
  .stats{grid-template-columns:1fr 1fr;margin-top:-1.25rem}
  .hero .wrap{padding:2.5rem 1rem 2.25rem}.band h1,.hero h1{font-size:1.7rem}
  .grid .card .cl{flex-direction:row}.grid .card .thw{width:108px;min-width:108px}.grid .card .th{width:108px;min-width:108px;aspect-ratio:auto;height:100%;object-fit:cover}
  .pn .btn,.mob-nav .btn{max-width:none}
  .ld>summary{display:flex;min-height:48px;align-items:center;padding:0 .5rem;font-weight:600;cursor:pointer}
}
.ld>summary{display:none}.mtoc{display:none}
@media(max-width:1180px){.mtoc{display:block;border:1px solid var(--line);border-radius:10px;margin:1rem 0}.mtoc summary{min-height:48px;display:flex;align-items:center;padding:0 1rem;font-weight:600;cursor:pointer}.mtoc ol{margin:0;padding:0 1rem 1rem 2.1rem}}
@media(max-width:960px){.ld>summary{display:flex;padding:0 .45rem}.lside{padding:.25rem .45rem}html,body{overflow-x:hidden}}
.notoc{grid-template-columns:250px minmax(0,1fr)}

/* contrast fixes on dark bands */
.dark-band .bc ol,.hero .bc ol,.lcover .bc ol{color:#d7e0ec}
.dark-band .bc a,.hero .bc a,.lcover .bc a{color:#fff;text-decoration:underline;text-underline-offset:2px}
.dark-band .bc li[aria-current],.hero .bc li[aria-current],.lcover .bc li[aria-current]{color:#fff;font-weight:600}
.dark-band .float a{color:var(--brand)}
.dark-band .float a.pri,.float a.pri{color:#fff}
.dark-band .float .btn.out{color:var(--brand);border-color:var(--brand);background:var(--bg)}
.dark-band .meta.lt,.dark-band .lt{color:#d7e0ec}

/* ===== v6 self-hosted font ===== */
@font-face{font-family:Inter;src:url('fonts/inter-var.woff2') format('woff2');font-weight:100 900;font-display:swap;font-style:normal}
html{font-size:100%}
body{font-family:Inter,system-ui,-apple-system,"Segoe UI",sans-serif;padding-bottom:calc(64px + env(safe-area-inset-bottom))}
h1{font-size:clamp(1.5rem,4vw,2.5rem)}
h2{font-size:clamp(1.2rem,3vw,1.4rem)}
.lead,.lead-plain{font-size:clamp(1rem,2.5vw,1.15rem);line-height:1.55;color:var(--muted);max-width:40ch}
input,select,textarea,button,.inp,.sbtn,.tb-btn{font-size:16px!important} /* prevent iOS zoom */
.inp,.srch input{min-height:44px}
.ta{min-height:6rem;padding:.75rem 1rem;width:100%;resize:vertical}

/* header hide on scroll */
.hd{transition:transform .25s ease}
.hd.head-hide{transform:translateY(-100%)}
@media(prefers-reduced-motion:reduce){.hd{transition:none}}

/* bottom tab bar — app-like mobile */
.tabbar{display:none;position:fixed;left:0;right:0;bottom:0;z-index:40;background:var(--bg);border-top:1px solid var(--line);
  padding:.25rem .25rem calc(.25rem + env(safe-area-inset-bottom));box-shadow:0 -4px 20px rgba(0,0,0,.08);
  justify-content:space-around;align-items:stretch;gap:0}
.tab{flex:1;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:.1rem;
  min-height:48px;min-width:44px;padding:.35rem .2rem;text-decoration:none;color:var(--muted);font-size:.68rem;font-weight:600;border-radius:10px}
.tab-ico{font-size:1.15rem;line-height:1}
.tab.on,.tab[aria-current=page]{color:var(--brand);background:var(--brand-s)}
.tab:hover{color:var(--brand)}
.mob-nav{display:none} /* replaced by large lesson buttons + tabbar */

/* lesson bottom sheet TOC */
.sheet-btn{display:none}
.sheet{display:none;position:fixed;inset:0;z-index:50}
.sheet.open{display:block}
.sheet-backdrop{position:absolute;inset:0;background:rgba(0,0,0,.45)}
.sheet-panel{position:absolute;left:0;right:0;bottom:0;max-height:78vh;overflow:auto;background:var(--bg);border-radius:16px 16px 0 0;
  padding:1rem 1rem calc(1rem + env(safe-area-inset-bottom));box-shadow:0 -8px 32px rgba(0,0,0,.2)}
.sheet-handle{width:40px;height:4px;background:var(--line);border-radius:4px;margin:0 auto .75rem}
.sheet-panel h2{margin:0 0 .75rem;font-size:1.1rem}
.les-actions{display:none;gap:.5rem;margin:1rem 0 5rem}
.les-actions .btn{flex:1;min-height:48px}

/* tools UI */
.tool-panel{display:grid;gap:1rem;margin:1.25rem 0}
.row-fields{display:grid;gap:1rem}
@media(min-width:700px){.row-fields{grid-template-columns:1fr 1fr}}
.contrast-preview{padding:1.5rem;border-radius:12px;border:1px solid var(--line);font-size:1.25rem;text-align:center;margin:.5rem 0}
.tool-card .tool-ico{width:64px;height:64px;margin:1rem 1rem 0;display:block}
.split-tool{display:grid;gap:1.25rem}
@media(min-width:900px){.split-tool{grid-template-columns:280px 1fr}}
.fake-app{background:var(--surf);border:1px solid var(--line);border-radius:12px;padding:1rem;display:grid;gap:.6rem}
.fake-brand{font-weight:700;margin:0;color:var(--brand)}.fake-h{margin:0;font-size:1.1rem}
.fake-app input{width:100%;min-height:44px;font-size:16px;border:1px solid var(--line);border-radius:8px;padding:0 .75rem;background:var(--bg);color:var(--fg)}
.fake-btn{min-height:44px;background:var(--brand);color:#fff;border:0;border-radius:8px;font-weight:600}
.fake-err{color:var(--bad);margin:0;font-weight:600}.fake-hint{margin:0;color:var(--muted);font-size:.85rem}
.heu-item{border:1px solid var(--line);border-radius:10px;padding:.85rem 1rem;margin:0 0 .75rem}
.opt-row{display:flex;flex-wrap:wrap;gap:.4rem}
.chip{display:inline-flex;align-items:center;gap:.35rem;min-height:44px;padding:0 .75rem;border:1px solid var(--line);border-radius:999px;background:var(--bg);cursor:pointer}
.chip:has(input:checked){background:var(--brand-s);border-color:var(--brand);color:var(--brand);font-weight:600}
.cardsort{display:grid;gap:1rem}.card-pool{list-style:none;margin:0;padding:.75rem;display:flex;flex-wrap:wrap;gap:.5rem;border:1px dashed var(--line);border-radius:12px;min-height:64px}
.sort-card{min-height:44px;padding:.55rem .9rem;border-radius:10px;background:var(--brand-s);border:1px solid var(--brand);cursor:grab;user-select:none;font-weight:600;color:var(--brand)}
.sort-card.held{outline:3px solid var(--focus);opacity:.9}
.sort-bins{display:grid;gap:.75rem}
@media(min-width:700px){.sort-bins{grid-template-columns:1fr 1fr}}
.sort-bin{border:1px solid var(--line);border-radius:12px;padding:.75rem;background:var(--surf);min-height:120px}
.bin-list{list-style:none;margin:.5rem 0 0;padding:0;display:flex;flex-wrap:wrap;gap:.4rem;min-height:44px}
.persona-card{scroll-margin-top:96px}
.mpiua-tool{display:grid;gap:1rem}
.diagram-scroll{overflow:auto;-webkit-overflow-scrolling:touch;max-width:100%;border:1px solid var(--line);border-radius:12px;padding:.5rem}
.mpiua-svg{width:min(320px,100%);height:auto;display:block;margin:0 auto;color:var(--brand)}
.mpiua-node circle{fill:var(--brand-s);stroke:var(--brand);stroke-width:2}
.mpiua-node.on circle,.mpiua-node:focus circle{fill:var(--brand)}
.mpiua-node text{fill:var(--fg);pointer-events:none}.mpiua-node.on text{fill:#fff}
.phase-tabs{display:flex;flex-wrap:wrap;gap:.4rem}
.phase-btn{min-height:44px;padding:.45rem .85rem;border-radius:999px;border:1px solid var(--line);background:var(--bg);color:var(--fg);font:inherit;font-weight:600;cursor:pointer}
.phase-btn[aria-selected=true]{background:var(--brand);color:#fff;border-color:var(--brand)}
.flash-card{position:relative;width:100%;min-height:200px;border:1px solid var(--line);border-radius:16px;background:var(--bg);box-shadow:var(--shadow);cursor:pointer;padding:1.5rem;text-align:left;font:inherit}
.flash-face{display:block}.flash-card .back{display:none}.flash-card.flipped .front{display:none}.flash-card.flipped .back{display:block}
.flash-nav .btn{flex:1}
.certificate{border:2px solid var(--brand);border-radius:16px;padding:2rem 1.5rem;text-align:center;margin:1.5rem 0;background:linear-gradient(180deg,var(--brand-s),var(--bg))}
.cert-name{font-size:1.75rem;font-weight:700;margin:.5rem 0}.cert-kicker{text-transform:uppercase;letter-spacing:.08em;font-size:.75rem;color:var(--brand);font-weight:700}
.chuleta-list{font-size:1.05rem;line-height:1.5}.chuleta-ico{margin:.5rem 0 1rem}
.ft-grid{display:grid;gap:1.25rem}@media(min-width:700px){.ft-grid{grid-template-columns:2fr 1fr}}
.ft-brand{display:flex;align-items:center;gap:.5rem;font-weight:700;color:var(--fg)}
.ft-links{list-style:none;margin:0;padding:0;display:flex;flex-wrap:wrap;gap:.5rem 1rem}
.ft-note{grid-column:1/-1}
.table-wrap,.diagram-scroll{max-width:100%;overflow-x:auto;-webkit-overflow-scrolling:touch}
.empty{padding:1.25rem;border:1px dashed var(--line);border-radius:12px;background:var(--surf);text-align:center;color:var(--muted)}
.icon-mod{width:40px;height:40px;border-radius:10px;vertical-align:middle;margin-right:.5rem}

@media(max-width:960px){
  .tabbar{display:flex}
  .nv,.a11y,.srch{/* keep srch */}
  .logo-txt{max-width:12ch;overflow:hidden;text-overflow:ellipsis}
  .sheet-btn{display:inline-flex;width:100%;margin:.75rem 0}
  .les .toc,.les .lside{display:none}
  .les{grid-template-columns:1fr;padding-bottom:6rem}
  .les-actions{display:flex}
  .pn{display:none}
  .hero .wrap{grid-template-columns:1fr;padding:2rem 1rem}
  .hero-card{order:-1}
  .stats{grid-template-columns:1fr 1fr;margin-top:-1rem}
  .grid,.g3,.out-grid{grid-template-columns:1fr}
  .band,.sec,.mcol,.les,.wrap{padding-left:max(1rem, env(safe-area-inset-left));padding-right:max(1rem, env(safe-area-inset-right))}
  body{overflow-x:hidden}
  .dk{grid-template-columns:1fr}
  .float{margin-top:1rem}
  .mcol>*{max-width:none}
}
@media(max-width:600px){
  .grid .card .cl{flex-direction:row;align-items:stretch}
  .grid .card .thw{width:96px;min-width:96px}
  .hdi{gap:.4rem}
  .menu-btn{margin-left:auto}
}
@media print{
  .hd,.tabbar,.a11y,.srch,.menu-btn,.mob-nav,.no-print,.sheet-btn,.les-actions,.skip{display:none!important}
  body{padding:0;background:#fff;color:#000}
  .certificate{break-inside:avoid}
  a[href]::after{content:""}
}

/* micro-interactions */
@media(prefers-reduced-motion:no-preference){
  .card{transition:transform .15s,box-shadow .15s}
  .btn{transition:background .15s,transform .1s}
  .btn:active{transform:scale(.98)}
  .flash-card{transition:box-shadow .2s}
}