/* ChemGem Chemistry II — same design system as the Chemistry I redesign (Oct 2026):
   paper + white surfaces, Lora headings, Inter body, teal brand, gold clues, blue worked examples,
   green checks, red gem. Layout: sticky bar, one wide column, lesson player with a progress rail. */
:root{
  --paper:#fbf9f4; --surface:#ffffff; --raise:#fdfbf7; --ink:#1f2d33; --muted:#5b6c71; --line:#e5e2d9;
  --navy:#1f6f5c; --navy-soft:#e5f2ed; --gold:#9a6b12; --gold-soft:#fbf1dc;
  --purple:#23758a; --purple-soft:#e4f1f4; --green:#2e7a4d; --green-soft:#e5f3ea;
  --blue:#2d6c95; --blue-soft:#e7f0f7; --slate:#55707a; --slate-soft:#eef2f2;
  --red:#b8202e; --red-soft:#fbe8ea; --on-accent:#ffffff; --shadow:0 1px 2px rgba(31,45,51,.05),0 10px 28px rgba(31,45,51,.08);
  --clue:#c8962e; --clue-soft:#fbefd2; --gem-red:var(--red);
  --display:"Lora",Georgia,"Times New Roman",serif;
  --body:"Inter","Segoe UI",system-ui,-apple-system,sans-serif;
  --s0:1.125rem; --s1:1.3rem; --s2:1.7rem; --s3:clamp(1.9rem,4vw,2.6rem); --s4:clamp(2.4rem,6.5vw,4.2rem);
  --r:14px; --gap:clamp(1.5rem,3vw,2.25rem);
  /* names the lesson figures already use */
  --bg:var(--paper); --accent:var(--gold); --accent-soft:var(--gold-soft); --calm:var(--navy); --calm-soft:var(--navy-soft);
  --ok:var(--green); --ok-soft:var(--green-soft); --no:var(--red); --no-soft:var(--red-soft);
  color-scheme:light;
}
@media (prefers-color-scheme: dark){:root:not([data-theme="light"]){
  --paper:#10171a; --surface:#172126; --raise:#1c282d; --ink:#e6eeec; --muted:#a3b4b1; --line:#2a3a3f;
  --navy:#6fd0b4; --navy-soft:#173029; --gold:#e8bb5c; --gold-soft:#2d2616;
  --purple:#7cc6d4; --purple-soft:#16303a; --green:#8fd4a5; --green-soft:#16301f;
  --blue:#93c2e3; --blue-soft:#172a38; --slate:#b3c6c3; --slate-soft:#1d292c;
  --red:#f07b82; --red-soft:#3a1d21; --on-accent:#10171a; --shadow:none; --clue:#e8bb5c; --clue-soft:#3a3018; color-scheme:dark}}
:root[data-theme="dark"]{
  --paper:#10171a; --surface:#172126; --raise:#1c282d; --ink:#e6eeec; --muted:#a3b4b1; --line:#2a3a3f;
  --navy:#6fd0b4; --navy-soft:#173029; --gold:#e8bb5c; --gold-soft:#2d2616;
  --purple:#7cc6d4; --purple-soft:#16303a; --green:#8fd4a5; --green-soft:#16301f;
  --blue:#93c2e3; --blue-soft:#172a38; --slate:#b3c6c3; --slate-soft:#1d292c;
  --red:#f07b82; --red-soft:#3a1d21; --on-accent:#10171a; --shadow:none; --clue:#e8bb5c; --clue-soft:#3a3018; color-scheme:dark}

*{box-sizing:border-box}
html{padding-top:env(safe-area-inset-top,0px);padding-bottom:env(safe-area-inset-bottom,0px)}
[hidden]{display:none!important}
body{margin:0;background:var(--paper);color:var(--ink);font-family:var(--body);font-size:var(--s0);line-height:1.7}
body::before{content:"";position:fixed;inset:0 0 auto;height:env(safe-area-inset-top,0px);z-index:25;background:var(--surface)}
img{max-width:100%}
h1,h2,h3,h4{font-family:var(--display);line-height:1.15;text-wrap:balance;margin:0;letter-spacing:-.01em;font-weight:600}
p{margin:0}
a{color:var(--blue)}
button{font:inherit;color:inherit}
:focus-visible{outline:3px solid var(--gold);outline-offset:3px;border-radius:6px}
sub,sup{font-size:.72em;line-height:0}
.wrap{max-width:74rem;margin:0 auto;padding-left:max(20px,env(safe-area-inset-left,0px));padding-right:max(20px,env(safe-area-inset-right,0px))}
.narrow{max-width:52rem}
.nw{white-space:nowrap}
.eyebrow{font-size:.8rem;letter-spacing:.14em;text-transform:uppercase;color:var(--muted);font-weight:700}
.muted,.note{color:var(--muted)}
.note{font-size:.92rem}
.lede{font-size:var(--s1);color:var(--muted);line-height:1.6;max-width:42rem}
.btn{display:inline-flex;align-items:center;justify-content:center;gap:.5rem;min-height:52px;padding:.7rem 1.4rem;border-radius:999px;border:2px solid var(--navy);background:var(--navy);color:var(--on-accent);font-weight:700;text-decoration:none;cursor:pointer;transition:transform .15s;text-align:center}
.btn:hover{transform:translateY(-1px)}
.btn.ghost{background:transparent;color:var(--navy)}
.btn.small{min-height:44px;padding:.45rem 1rem;font-size:1rem}
.btns{display:flex;gap:.75rem;flex-wrap:wrap;align-items:center}
.free-ticks{display:flex;flex-wrap:wrap;gap:.4rem 1.2rem;list-style:none;padding:0;margin:1.1rem 0 0;color:var(--muted);font-size:.95rem}
.free-ticks li::before{content:"✓ ";color:var(--green);font-weight:700}
.pro-badge{display:block;max-width:34em;margin:0;font-family:var(--display);font-weight:700;font-size:clamp(1.15rem,2.4vw,1.45rem);line-height:1.3;color:var(--gem-red)}
.book-line{margin:1.1rem 0 0;font-weight:800;font-size:clamp(1.05rem,2.2vw,1.3rem);letter-spacing:.02em;color:var(--navy);text-transform:uppercase;line-height:1.35}
.work-band{background:var(--clue-soft);color:var(--ink);font:600 .85rem/1.3 var(--body);text-align:center;border-bottom:1px solid var(--line)}
.work-band .wrap{padding-block:.5rem}
.work-band b{color:var(--red)}

/* ---------- top bar ---------- */
.bar{position:sticky;top:env(safe-area-inset-top,0px);z-index:20;background:color-mix(in srgb,var(--surface) 92%,transparent);backdrop-filter:blur(8px);border-bottom:1px solid var(--line)}
.bar .wrap{display:flex;align-items:center;gap:1rem;min-height:84px}
.brand{display:flex;align-items:center;gap:.65rem;text-decoration:none;color:var(--ink);margin-right:auto}
.brand b{font-family:var(--display);font-weight:600;font-size:1.8rem;color:var(--navy);white-space:nowrap;display:flex;align-items:center}
.brand-gem{height:.85em;width:auto;margin-left:.3rem}
.brand-sub{font-size:.85rem;color:var(--muted);border-left:1px solid var(--line);padding-left:.65rem;white-space:nowrap}
.nav{display:flex;gap:.25rem}
.nav a{text-decoration:none;color:var(--muted);padding:.6rem 1rem;border-radius:999px;font-weight:700;font-size:1.05rem;white-space:nowrap}
.nav a:hover{color:var(--ink)}
.nav a[aria-current="page"]{background:var(--navy-soft);color:var(--navy)}
.nav a.nav-buy{border:1.5px solid var(--navy);color:var(--navy)}
@media (max-width:1180px){.nav a{padding:.5rem .7rem;font-size:1rem}}
@media (max-width:1040px){
  .bar .wrap{flex-wrap:wrap;row-gap:0;padding-top:.4rem;min-height:0}
  .nav{order:2;width:100%;flex-wrap:nowrap;overflow-x:auto;scrollbar-width:none;padding-bottom:.4rem;-webkit-mask-image:linear-gradient(90deg,#000 88%,transparent);mask-image:linear-gradient(90deg,#000 88%,transparent)}
  .nav::-webkit-scrollbar{display:none}
  .nav a{flex:none}
}
@media (max-width:560px){.brand b{font-size:1.5rem}.brand-sub{font-size:.78rem}}

main{min-height:60vh}
.page{padding-block:2.5rem 5rem;display:grid;gap:2.5rem}
.page-head{display:grid;gap:.6rem}
.page-head h1{font-size:var(--s3)}
.crumbs{font-size:.95rem;color:var(--muted)}
.crumbs a{color:var(--muted)}
footer{padding-block:2.5rem;color:var(--muted);font-size:.95rem;border-top:1px solid var(--line)}
footer .wrap{display:flex;flex-wrap:wrap;gap:.5rem 1.5rem;justify-content:space-between}

/* ======================= HOME ======================= */
.home .band{padding-block:clamp(3.25rem,7vw,5.5rem)}
.home .band.alt{background:var(--surface);border-block:1px solid var(--line)}
.home .band h2{font-size:var(--s3);margin:.45rem 0 0;max-width:42rem}
.home .eyebrow{font-size:.85rem}
.home .f-lede{margin-top:.7rem;color:var(--muted);max-width:40rem;line-height:1.55}
/* 1. hero */
.f-hero{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1.02fr);gap:clamp(2rem,4.5vw,4rem);align-items:start;padding-block:clamp(1.25rem,3vw,2.5rem) clamp(1.5rem,3vw,2.5rem)}
.f-copy{padding-top:clamp(0rem,1.5vw,1rem)}
.f-author{margin:.65rem 0 0;font-size:1rem;line-height:1.5;color:var(--muted);max-width:32rem}
.f-h1{margin:1rem 0 0;font-size:var(--s4);line-height:1.07}
.f-h1 em{font-style:normal;color:var(--gem-red)}
.f-hero .book-line{margin-top:.9rem}
/* 2. "What do you need?" */
.f-card{background:var(--surface);border:1px solid var(--line);border-radius:22px;box-shadow:var(--shadow);padding:clamp(1rem,2.2vw,1.5rem);display:grid;gap:.85rem;scroll-margin-top:110px;min-width:0}
.f-card:focus{outline:none}
.f-card-h{font-size:var(--s2)}
.f-moments{list-style:none;margin:0;padding:0;display:grid;gap:.5rem}
.f-m{border:1px solid var(--line);border-radius:16px;background:var(--raise);transition:border-color .2s,background .2s;min-width:0}
.f-m.open{border-color:color-mix(in srgb,var(--c) 60%,var(--line));background:var(--surface);box-shadow:inset 4px 0 0 var(--c)}
.f-mbtn{width:100%;display:flex;align-items:center;gap:.8rem;min-height:60px;padding:.55rem .9rem .55rem .65rem;border:0;background:none;border-radius:16px;color:var(--ink);text-align:left;cursor:pointer}
.f-mbtn:hover .f-mt b{color:var(--navy)}
.f-mic{flex:none;width:2.5rem;height:2.5rem;border-radius:12px;display:grid;place-items:center;background:var(--cs);color:var(--c)}
.f-mic svg{width:1.4rem;height:1.4rem;fill:none;stroke:currentColor;stroke-width:2;stroke-linecap:round;stroke-linejoin:round}
.f-mt{flex:1;min-width:0;display:grid;gap:.05rem;line-height:1.3}
.f-mt b{font-size:1.08rem}
.f-mt span{font-size:.92rem;color:var(--muted)}
.f-chev{flex:none;width:.65rem;height:.65rem;border-right:2.5px solid var(--muted);border-bottom:2.5px solid var(--muted);transform:rotate(45deg) translate(-2px,-2px);transition:transform .2s}
.f-mbtn[aria-expanded="true"] .f-chev{transform:rotate(225deg) translate(-2px,-2px)}
.f-panel{display:grid;gap:.85rem;padding:.2rem 1rem 1.05rem 1.1rem;animation:fIn .22s ease-out;min-width:0}
@keyframes fIn{from{opacity:.2;transform:translateY(3px)}to{opacity:1;transform:none}}
.f-resume{display:flex;flex-wrap:wrap;align-items:center;gap:.5rem 1rem;padding:.7rem .9rem;border-radius:14px;background:var(--navy-soft);border:1px solid color-mix(in srgb,var(--navy) 30%,transparent)}
.f-resume p{margin:0;flex:1 1 13rem;line-height:1.4}
.f-rk{display:block;font-size:.85rem;font-weight:700;letter-spacing:.06em;text-transform:uppercase;color:var(--navy)}
.f-resume b{font-family:var(--display);font-size:1.15rem;font-weight:600}
.f-ask{display:flex;flex-wrap:wrap;align-items:center;gap:.3rem .55rem;font-weight:700;font-size:1.05rem;line-height:1.35}
.f-askhint{font-weight:500;font-size:.95rem;color:var(--muted)}
.f-n{flex:none;display:grid;place-items:center;width:1.8rem;height:1.8rem;border-radius:50%;background:var(--navy-soft);color:var(--navy);font-size:.95rem}
.f-chips{display:flex;flex-wrap:wrap;gap:.45rem}
.f-chip{min-height:44px;padding:.4rem .9rem;border-radius:999px;border:2px solid var(--line);background:var(--paper);color:var(--ink);font-weight:600;font-size:.95rem;cursor:pointer;transition:border-color .15s,background .15s}
.f-chip:hover{border-color:var(--clue)}
.f-chip[aria-pressed="true"]{border-color:var(--clue);background:var(--clue-soft)}
.f-sel{display:grid;gap:.35rem;font-size:.95rem;color:var(--muted);font-weight:600}
.f-sel select{width:100%;min-width:0;min-height:48px;padding:.4rem .7rem;border-radius:12px;border:2px solid var(--line);background:var(--paper);color:var(--ink);font:inherit;font-size:1rem;font-weight:500}
.f-out{display:grid;gap:.8rem;min-width:0}
.f-out:empty{display:none}
.f-out.swap{animation:fIn .22s ease-out}
.f-hint{padding:.75rem .95rem;border-radius:12px;background:var(--cs,var(--clue-soft));line-height:1.5}
.f-ptitle{display:flex;flex-wrap:wrap;align-items:baseline;gap:.15rem .6rem;font-family:var(--display);font-size:1.2rem;font-weight:600;line-height:1.3}
.f-ptitle small{font-family:var(--body);font-size:.88rem;font-weight:600;color:var(--muted)}
.f-out .btn{justify-self:start;max-width:100%}
.f-why{font-size:.95rem;color:var(--muted);line-height:1.5}
.f-k{font-size:.85rem;letter-spacing:.1em;text-transform:uppercase;font-weight:700;color:var(--navy)}
.lookfor{display:grid;gap:.6rem;padding:.9rem 1.05rem;border-radius:var(--r);background:var(--clue-soft);border:1px solid color-mix(in srgb,var(--clue) 40%,var(--line));border-left:5px solid var(--clue);line-height:1.55}
.lookfor .lk{font-size:.8rem;letter-spacing:.1em;text-transform:uppercase;font-weight:800;color:color-mix(in srgb,var(--clue) 70%,var(--ink))}
.lf-path{margin:0;padding:0;list-style:none;display:grid;gap:.35rem;counter-reset:lp}
.lf-path li{counter-increment:lp;display:grid;grid-template-columns:1.6rem minmax(0,1fr);gap:.5rem;line-height:1.45}
.lf-path li::before{content:counter(lp);width:1.45rem;height:1.45rem;border-radius:50%;display:grid;place-items:center;background:var(--gold);color:var(--on-accent);font-size:.8rem;font-weight:800;margin-top:.1rem}
.f-days{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:.45rem}
.f-opt,.f-chap{min-height:48px;padding:.45rem .7rem;border-radius:12px;border:2px solid var(--line);background:var(--paper);color:var(--ink);font-weight:600;font-size:.95rem;line-height:1.25;cursor:pointer;transition:border-color .15s,background .15s}
.f-opt:hover,.f-chap:hover{border-color:var(--navy)}
.f-opt[aria-pressed="true"],.f-chap[aria-pressed="true"]{background:var(--navy);border-color:var(--navy);color:var(--on-accent)}
.f-chaps{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:.4rem}
.f-chap{display:flex;align-items:center;gap:.5rem;text-align:left;padding-left:.4rem}
.f-cn{flex:none;display:grid;place-items:center;width:1.8rem;height:1.8rem;border-radius:50%;background:var(--navy-soft);color:var(--navy);font-weight:700;font-size:.9rem}
.f-chap[aria-pressed="true"] .f-cn{background:var(--on-accent);color:var(--navy)}
.f-free{margin-left:auto;font-size:.85rem;font-weight:700;color:var(--green)}
.f-chap[aria-pressed="true"] .f-free{color:inherit}
.f-plan,.f-night{display:grid;gap:.7rem;padding:1rem;border-radius:14px;background:var(--navy-soft);border:1px solid color-mix(in srgb,var(--navy) 28%,transparent);animation:fIn .22s ease-out;min-width:0}
.f-night{background:var(--purple-soft);border-color:color-mix(in srgb,var(--purple) 28%,transparent)}
.f-night .f-k{color:var(--purple)}
.f-sumline{font-family:var(--display);font-size:1.3rem;font-weight:600;line-height:1.25}
.f-start{justify-self:start;max-width:100%}
.f-sub{font-weight:700;font-size:.95rem}
.f-sub span{font-weight:500;color:var(--muted)}
.f-list{display:grid;gap:.7rem}
.f-gh{font-size:.9rem;font-weight:700;color:var(--muted);margin-bottom:.3rem}
.f-grp ul{list-style:none;margin:0;padding:0;display:grid;gap:.3rem}
.f-grp li{display:flex;align-items:stretch;background:var(--surface);border:1px solid var(--line);border-radius:12px;overflow:hidden}
.f-grp li.off{opacity:.6}
.f-grp li.off a{text-decoration:line-through}
.f-tog{flex:none;width:46px;min-height:46px;border:0;border-right:1px solid var(--line);background:color-mix(in srgb,var(--navy) 10%,transparent);color:var(--navy);font-weight:700;font-size:1.05rem;cursor:pointer}
.f-grp li.off .f-tog{background:transparent}
.f-grp a{flex:1;min-width:0;display:flex;align-items:center;gap:.55rem;padding:.4rem .75rem;color:var(--ink);text-decoration:none;font-size:.98rem;line-height:1.3}
.f-grp a:hover{color:var(--navy)}
.f-tn{flex:none;font-variant-numeric:tabular-nums;font-weight:700;color:var(--navy);min-width:2.4rem}
.f-done{margin-left:auto;font-size:.85rem;font-weight:700;color:var(--green)}
.f-final{display:flex;align-items:center;gap:.8rem;min-height:52px;padding:.6rem .9rem;border-radius:12px;background:var(--surface);border:2px solid var(--green);color:var(--ink);text-decoration:none;line-height:1.3}
.f-final span span{font-size:.92rem;color:var(--muted)}
.f-fk{flex:none;font-size:.85rem;text-transform:uppercase;letter-spacing:.06em;font-weight:700;color:var(--green)}
.f-arr{margin-left:auto;color:var(--green);font-weight:700}
.f-saved{display:flex;flex-wrap:wrap;align-items:center;gap:0 .8rem;font-size:.92rem;color:var(--muted)}
.f-saved>span::before{content:"✓ ";color:var(--green);font-weight:700}
.f-link{background:none;border:0;padding:0;min-height:44px;font-weight:700;color:var(--navy);text-decoration:underline;cursor:pointer}
.f-nlist{list-style:none;margin:0;padding:0;display:grid;gap:.5rem}
.f-nch{font-size:.9rem;font-weight:700;color:var(--muted);padding-top:.3rem}
.f-nt{display:grid;gap:.25rem;padding:.35rem .8rem;border-radius:12px;background:var(--surface);border:1px solid var(--line)}
.f-nt details>summary{display:flex;gap:.6rem;align-items:center;min-height:44px;cursor:pointer;list-style:none;font-weight:600;line-height:1.3}
.f-nt details>summary::-webkit-details-marker{display:none}
.f-nt details>summary::after{content:"+";margin-left:auto;color:var(--purple);font-weight:800;font-size:1.2rem}
.f-nt details[open]>summary::after{content:"−"}
.f-nt .lookfor{margin:.2rem 0 .5rem}
.f-nt .f-open{display:inline-flex;align-items:center;min-height:44px;font-weight:700;color:var(--navy)}
.f-pick{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:.55rem}
.f-pick-opt{display:grid;gap:.1rem;align-content:start;min-height:44px;padding:.8rem .95rem;border-radius:14px;border:2px solid var(--blue);background:var(--blue-soft);color:var(--ink);text-decoration:none;line-height:1.3;transition:transform .15s}
.f-pick-opt:hover{transform:translateY(-1px)}
.f-pick-opt b{font-family:var(--display);font-size:1.15rem;color:var(--blue)}
.f-pick-opt>span:last-child{font-size:.9rem;color:var(--muted)}
.f-pick-tag{font-size:.85rem;font-weight:800;letter-spacing:.06em;text-transform:uppercase;color:var(--blue)}
/* 3. method flow */
.f-how{padding-top:clamp(1.75rem,3.5vw,2.5rem)}
.f-how-top{display:flex;justify-content:space-between;align-items:flex-end;gap:1rem;flex-wrap:wrap}
.f-pause{display:inline-flex;align-items:center;gap:.45rem;min-height:44px;padding:.3rem .95rem;border-radius:999px;border:1px solid var(--line);background:var(--paper);color:var(--muted);font-size:.92rem;font-weight:700;cursor:pointer}
.f-pause:hover{color:var(--ink);border-color:var(--muted)}
.f-pause-ic{width:.7rem;height:.8rem;border-left:3px solid currentColor;border-right:3px solid currentColor}
.f-pause[aria-pressed="true"] .f-pause-ic{border:0;width:0;height:0;border-top:.42rem solid transparent;border-bottom:.42rem solid transparent;border-left:.7rem solid currentColor}
.f-flow{margin:1.75rem 0 0}
.f-steps{list-style:none;margin:0;padding:0;display:grid;grid-template-columns:minmax(0,1fr) 3.25rem minmax(0,1fr) 3.25rem minmax(0,1fr);align-items:start}
.f-step{display:grid;gap:.9rem;align-content:start;padding:.8rem;border-radius:18px;border:2px solid transparent;transition:border-color .4s,background .4s;min-width:0}
.f-say{display:grid;gap:.3rem}
.f-say>p:last-child{color:var(--muted);line-height:1.5}
.f-num{display:flex;align-items:center;gap:.55rem;font-family:var(--display);font-weight:600;font-size:var(--s1);line-height:1.2}
.f-num span{flex:none;width:1.9rem;height:1.9rem;border-radius:50%;display:grid;place-items:center;background:var(--c);color:var(--on-accent);font-family:var(--body);font-size:.95rem;font-weight:800}
.f-arrow{height:7rem;margin-top:calc(.8rem + 2px);display:grid;place-items:center}
.f-arrow span{position:relative;width:100%;height:3px;background:color-mix(in srgb,var(--muted) 45%,transparent);border-radius:2px}
.f-arrow span::after{content:"";position:absolute;top:50%;right:-3px;transform:translateY(-50%);border-top:6px solid transparent;border-bottom:6px solid transparent;border-left:9px solid color-mix(in srgb,var(--muted) 45%,transparent);transition:border-color .4s}
.f-arrow span::before{content:"";position:absolute;inset:0;background:var(--navy);border-radius:2px;transform:scaleX(0);transform-origin:left;transition:transform .6s ease}
.f-mock{display:grid;grid-template-columns:minmax(0,1fr);gap:.5rem;align-content:center;height:7rem;padding:.75rem .9rem;border-radius:14px;background:var(--surface);border:1px solid var(--line);border-top:5px solid var(--c)}
.f-mock i{display:block;height:.6rem;border-radius:4px;background:color-mix(in srgb,var(--muted) 26%,transparent)}
.f-qhead{display:flex;justify-content:space-between}
.f-qhead i{width:30%;height:.45rem!important;background:color-mix(in srgb,var(--muted) 16%,transparent)!important}
.f-qhead i+i{width:18%}
.f-line{display:flex;gap:.4rem;align-items:center}
.f-line i{flex-grow:0;flex-shrink:1}
.f-line i.k{transition:background .45s}
.f-route{gap:.3rem;padding-block:.45rem}
.f-rchip{display:inline-flex;align-items:center;gap:.45rem;justify-self:start;padding:.12rem .6rem .12rem .15rem;border-radius:999px;background:var(--gold-soft);border:1px solid color-mix(in srgb,var(--gold) 45%,transparent);transition:opacity .4s}
.f-rchip:nth-child(2){margin-left:1rem}
.f-rchip:nth-child(3){margin-left:2rem}
.f-rchip b{width:1.3rem;height:1.3rem;border-radius:50%;display:grid;place-items:center;background:var(--gold);color:var(--on-accent);font-size:.85rem}
.f-rchip i{background:color-mix(in srgb,var(--gold) 40%,transparent)!important;height:.45rem!important}
.f-opts{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:.4rem}
.f-opts i{height:1.5rem!important;border-radius:8px!important;background:var(--paper)!important;border:2px solid var(--line);transition:border-color .4s,background .4s}
.f-whyrow{display:flex;gap:.45rem;align-items:center;min-width:0;padding:.3rem .55rem;border-left:4px solid var(--green);background:var(--green-soft);border-radius:0 8px 8px 0;font-size:.9rem;line-height:1.2;white-space:nowrap;overflow:hidden;transition:opacity .45s}
.f-check{flex:none;width:1.35rem;height:1.35rem;border-radius:50%;display:grid;place-items:center;background:var(--green);color:var(--on-accent);font-size:.85rem;font-weight:800}
.f-whyrow b{color:var(--green)}
.f-whyt{color:var(--muted);overflow:hidden}
.f-flow[data-phase="1"] .f-s1,.f-flow[data-phase="2"] .f-s2,.f-flow.playing[data-phase="3"] .f-s3{border-color:color-mix(in srgb,var(--c) 55%,transparent);background:var(--cs)}
.f-flow:not([data-phase="0"]) .f-line i.k{background:var(--clue)}
.f-flow[data-phase="0"] .f-rchip,.f-flow[data-phase="1"] .f-rchip{opacity:.3}
.f-flow[data-phase="2"] .f-rchip:nth-child(2){transition-delay:.35s}
.f-flow[data-phase="2"] .f-rchip:nth-child(3){transition-delay:.7s}
.f-flow[data-phase="3"] .f-opts i.ok{border-color:var(--green);background:var(--green-soft)!important}
.f-flow:not([data-phase="3"]) .f-whyrow{opacity:.3}
.f-flow[data-phase="2"] .f-arrow:nth-child(2) span::before,.f-flow[data-phase="3"] .f-arrow span::before{transform:scaleX(1)}
.f-flow[data-phase="2"] .f-arrow:nth-child(2) span::after,.f-flow[data-phase="3"] .f-arrow span::after{border-left-color:var(--navy)}
.f-loop{margin-top:1.5rem;padding:.8rem 1.1rem;border:2px dashed color-mix(in srgb,var(--green) 55%,var(--line));border-radius:14px;max-width:40rem;display:flex;gap:.7rem;align-items:center;line-height:1.45;font-weight:600}
.f-loop span{font-size:1.4rem;color:var(--green);font-weight:700}
/* 4. sounds familiar */
.f-pain-grid{display:grid;grid-template-columns:minmax(0,1.15fr) minmax(0,1fr);gap:clamp(2rem,5vw,4rem);margin-top:1.75rem;align-items:start}
.f-lines{list-style:none;margin:0;padding:0}
.f-lines li{padding:.85rem 0;border-bottom:1px solid var(--line);font-family:var(--display);font-size:var(--s1);line-height:1.4}
.f-lines li:first-child{padding-top:0}
.f-foryou{display:grid;gap:.85rem}
.f-foryou h3{font-size:var(--s1)}
.f-foryou ul{margin:0;padding:0;list-style:none;display:grid;gap:.5rem}
.f-foryou li{padding-left:1.6rem;position:relative;line-height:1.5}
.f-foryou li::before{content:"✓";position:absolute;left:0;color:var(--green);font-weight:800}
.f-cta{justify-self:start;margin-top:.35rem}
/* 5. tools by stage */
.f-stages{display:grid;grid-template-columns:2fr 2fr 1fr;gap:1rem;margin-top:2rem;align-items:stretch}
.f-stage{display:grid;grid-template-rows:auto 1fr;gap:.85rem;min-width:0}
.f-stage-k{display:flex;align-items:center;gap:.6rem;font-size:.9rem;letter-spacing:.1em;text-transform:uppercase;font-weight:800;color:var(--sc)}
.f-stage-k::before{content:"";flex:none;width:.85rem;height:.85rem;border-radius:50%;border:3px solid var(--sc);background:var(--surface)}
.f-stage-k::after{content:"";flex:1;height:3px;border-radius:3px;background:color-mix(in srgb,var(--sc) 45%,transparent)}
.f-tiles{list-style:none;margin:0;padding:0;display:grid;grid-template-columns:repeat(var(--n),minmax(0,1fr));gap:1rem}
.f-tile{height:100%;display:flex;flex-direction:column;gap:.45rem;padding:.95rem .95rem 1.1rem;border-radius:18px;background:var(--paper);border:1px solid var(--line);border-top:5px solid var(--c);color:var(--ink);text-decoration:none;transition:transform .15s,border-color .15s;cursor:pointer;text-align:left;width:100%;font:inherit}
.f-tile:hover{transform:translateY(-2px);border-color:var(--c)}
.f-tile>b{font-family:var(--display);font-size:1.2rem;margin-top:.3rem}
.f-td{color:var(--muted);font-size:.95rem;line-height:1.45}
.f-go{margin-top:auto;padding-top:.35rem;font-weight:700;color:var(--c);font-size:.95rem}
.f-prev{display:grid;gap:.4rem;align-content:center;height:7rem;padding:.75rem;border-radius:12px;background:var(--cs);min-width:0}
.f-prev i{display:block;height:.5rem;border-radius:3px;background:color-mix(in srgb,var(--c) 32%,transparent)}
.f-p-lesson i.h{width:55%;height:.7rem;background:var(--c)}
.f-p-lesson .ex{display:grid;gap:.3rem;padding:.4rem .5rem;border-left:3px solid var(--c);background:var(--surface);border-radius:0 6px 6px 0}
.f-p-hint .tip{justify-self:end;padding:.05rem .6rem;border-radius:999px;background:var(--c);color:var(--on-accent);font-size:.85rem;font-weight:800;line-height:1.4}
.f-p-hint .o,.f-p-exam .o{height:1rem;border-radius:6px;background:var(--surface);border:1.5px solid color-mix(in srgb,var(--c) 30%,var(--line))}
.f-p-cards{place-items:center}
.f-p-cards .c{grid-area:1/1;width:76%;height:4.4rem;border-radius:10px;background:var(--surface);border:1.5px solid color-mix(in srgb,var(--c) 35%,var(--line))}
.f-p-cards .c2{transform:translate(7px,6px);opacity:.65}
.f-p-cards .c1{position:relative;display:grid;gap:.35rem;align-content:center;justify-items:center;padding:.5rem}
.f-p-cards .c1 i{width:70%}
.f-p-cards .flip{position:absolute;right:.35rem;bottom:.15rem;font-size:.95rem;font-weight:800;color:var(--c);line-height:1}
.f-p-exam .bar2{height:.45rem;border-radius:3px;background:var(--surface);overflow:hidden}
.f-p-exam .bar2 i{width:40%;height:100%;background:var(--c)}
.f-p-exam .row,.f-p-find .r{display:flex;gap:.45rem;align-items:center;min-width:0}
.f-p-exam .row i,.f-p-find .r i{flex:1}
.f-prev em{font-style:normal;font-size:.85rem;font-weight:800;color:var(--c);line-height:1.2}
.f-p-find .s{display:flex;gap:.45rem;align-items:center;height:1.6rem;padding:0 .55rem;border-radius:999px;background:var(--surface)}
.f-p-find .lens{flex:none;width:.7rem;height:.7rem;border:2px solid var(--muted);border-radius:50%}
.f-p-find .s i{flex:1;background:color-mix(in srgb,var(--muted) 20%,transparent)}
.f-p-find .r{padding:.2rem .35rem;border-radius:6px}
.f-p-find .r.on{background:var(--surface)}
/* 6. depth */
.f-stats{list-style:none;margin:1.75rem 0 0;padding:0;display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:1rem}
.f-stats li{display:grid;gap:.25rem;align-content:start;padding:1.1rem 1.2rem;border-radius:var(--r);background:var(--surface);border:1px solid var(--line)}
.f-stats b{font-family:var(--display);font-size:var(--s3);font-weight:600;color:var(--navy);line-height:1.1}
.f-stats span{color:var(--muted);line-height:1.4}
.f-chlist{list-style:none;margin:1.75rem 0 0;padding:0;display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:0 1.75rem}
.f-chlist a{display:flex;gap:.8rem;align-items:center;min-height:52px;padding:.45rem .2rem;border-bottom:1px solid var(--line);color:var(--ink);text-decoration:none}
.f-chlist a:hover .f-chn{color:var(--navy);text-decoration:underline}
.f-chk{flex:none;width:2rem;font-family:var(--display);font-weight:600;font-size:1.25rem;color:var(--purple);font-variant-numeric:tabular-nums}
.f-chn{flex:1;min-width:0;line-height:1.35}
.f-chf{flex:none;font-size:.8rem;font-weight:800;letter-spacing:.06em;text-transform:uppercase;color:var(--green);background:var(--green-soft);padding:.1rem .55rem;border-radius:999px}
.f-cha{flex:none;color:var(--muted);font-weight:700}
/* 7. price */
.f-tiers{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:1rem;margin-top:1.75rem;align-items:stretch}
.f-tier{display:grid;gap:.6rem;align-content:start;padding:1.4rem;border-radius:18px;border:1px solid var(--line);background:var(--paper)}
.f-tier-free{border:2px solid var(--green);background:var(--green-soft)}
.f-tag{font-size:.85rem;font-weight:800;letter-spacing:.1em;text-transform:uppercase;color:var(--muted)}
.f-tier-free .f-tag{color:var(--green)}
.f-amt{font-family:var(--display);font-size:2.4rem;font-weight:600;line-height:1}
.f-tier ul{margin:0;padding:0;list-style:none;display:grid;gap:.3rem;line-height:1.45}
.f-tier li{padding-left:1.4rem;position:relative}
.f-tier li::before{content:"✓";position:absolute;left:0;color:var(--green);font-weight:800}
.f-kit{margin-top:1.25rem;line-height:1.6}
/* 8. who */
.f-who-card{display:grid;grid-template-columns:auto minmax(0,1fr);gap:clamp(1.25rem,4vw,2.5rem);align-items:center;max-width:52rem}
.f-photo{width:clamp(6.5rem,13vw,9rem);aspect-ratio:1;border-radius:50%;overflow:hidden;display:grid;place-items:center;background:var(--navy-soft);border:3px solid var(--surface);box-shadow:0 0 0 2px var(--navy)}
.f-photo svg{width:58%;height:auto}
.f-who-copy{display:grid;gap:.55rem}
.f-cred{font-weight:600;color:var(--navy)}
.f-who-copy p:last-child{color:var(--muted);line-height:1.6;max-width:38rem}
/* 9. FAQ */
.f-qa{display:grid;gap:.6rem;margin-top:1.75rem;max-width:46rem}
.f-qa details{border:1px solid var(--line);border-radius:14px;background:var(--paper)}
.f-qa summary{list-style:none;cursor:pointer;min-height:56px;display:flex;align-items:center;justify-content:space-between;gap:1rem;padding:.7rem 1.1rem;font-weight:700;line-height:1.35}
.f-qa summary::-webkit-details-marker{display:none}
.f-qa summary::after{content:"+";flex:none;font-size:1.4rem;color:var(--navy);line-height:1}
.f-qa details[open] summary::after{content:"−"}
.f-qa details p{padding:0 1.1rem 1rem;color:var(--muted);line-height:1.6}
/* 10. closing */
.f-close{text-align:center;background:var(--navy-soft)!important;border-top:1px solid var(--line)}
.f-close h2{margin-inline:auto!important}
.f-closerow{list-style:none;margin:1.6rem auto 0;padding:0;display:flex;flex-wrap:wrap;justify-content:center;gap:.6rem;max-width:62rem}
.f-ctile{min-height:52px;padding:.55rem 1.15rem;border-radius:14px;border:2px solid var(--c);background:var(--surface);color:var(--ink);font-weight:700;font-size:1rem;cursor:pointer;box-shadow:inset 0 -4px 0 var(--c);transition:transform .15s}
.f-ctile:hover{transform:translateY(-1px)}
.f-closeticks{justify-content:center;margin-top:1.25rem}
@media (max-width:1100px){
  .f-stages{grid-template-columns:minmax(0,1fr) minmax(0,1fr)}
  .f-stage:last-child{grid-column:1/-1}
  .f-stage:last-child .f-tiles{grid-template-columns:minmax(0,1fr) minmax(0,1fr)}
}
@media (max-width:900px){
  .f-hero{grid-template-columns:minmax(0,1fr);gap:1.4rem}
  .f-steps{grid-template-columns:minmax(0,1fr)}
  .f-step{grid-template-columns:8.5rem minmax(0,1fr);align-items:center;gap:1rem;padding:.6rem}
  .f-mock{height:6.5rem;padding:.6rem .65rem;gap:.4rem}
  .f-arrow{height:1.9rem;margin-top:0;width:8.5rem;margin-left:calc(.6rem + 2px)}
  .f-arrow span{width:3px;height:100%}
  .f-arrow span::after{top:auto;right:auto;left:50%;bottom:-3px;transform:translateX(-50%);border-left:6px solid transparent;border-right:6px solid transparent;border-top:9px solid color-mix(in srgb,var(--muted) 45%,transparent);border-bottom:0}
  .f-flow[data-phase="2"] .f-arrow:nth-child(2) span::after,.f-flow[data-phase="3"] .f-arrow span::after{border-left-color:transparent;border-top-color:var(--navy)}
  .f-arrow span::before{transform:scaleY(0);transform-origin:top}
  .f-flow[data-phase="2"] .f-arrow:nth-child(2) span::before,.f-flow[data-phase="3"] .f-arrow span::before{transform:scaleY(1)}
  .f-rchip:nth-child(2){margin-left:.5rem}
  .f-rchip:nth-child(3){margin-left:1rem}
  .f-rchip i{max-width:2.4rem}
  .f-whyt{display:none}
  .f-pain-grid{grid-template-columns:minmax(0,1fr)}
  .f-stats{grid-template-columns:repeat(2,minmax(0,1fr))}
  .f-tiers{grid-template-columns:minmax(0,1fr)}
}
@media (max-width:640px){
  .f-stages{grid-template-columns:minmax(0,1fr)}
  .f-tiles,.f-stage:last-child .f-tiles{grid-template-columns:minmax(0,1fr)}
  .f-tile{display:grid;grid-template-columns:6.75rem minmax(0,1fr);column-gap:.9rem;row-gap:.2rem;align-items:start;align-content:start}
  .f-tile .f-prev{grid-row:1/span 3;height:6.75rem;padding:.6rem}
  .f-tile>b{margin-top:0}
  .f-tile .f-go{grid-column:2;margin-top:.2rem;padding-top:0}
}
@media (max-width:520px){
  .f-hero{padding-top:.85rem;gap:1.05rem}
  .pro-badge{font-size:1.05rem}
  .f-author{font-size:.92rem;margin-top:.4rem}
  .f-h1{font-size:2.3rem;margin-top:.6rem}
  .f-hero .book-line{font-size:.98rem;margin-top:.55rem}
  .f-card{padding:.85rem .75rem;border-radius:18px;gap:.7rem}
  .f-card-h{font-size:1.45rem;padding-left:.2rem}
  .f-mbtn{min-height:58px;padding:.45rem .7rem .45rem .5rem;gap:.7rem}
  .f-panel{padding:.1rem .7rem .9rem .8rem}
  .f-days{grid-template-columns:repeat(2,minmax(0,1fr))}
  .f-chaps,.f-pick{grid-template-columns:minmax(0,1fr)}
  .f-start,.f-out .btn,.f-cta{width:100%;justify-self:stretch}
  .f-step{grid-template-columns:7rem minmax(0,1fr);gap:.8rem}
  .f-arrow{width:7rem}
  .f-lines li{font-size:1.15rem}
  .f-chlist{grid-template-columns:minmax(0,1fr)}
  .f-who-card{grid-template-columns:minmax(0,1fr);justify-items:start}
  .f-closerow{display:grid;grid-template-columns:minmax(0,1fr);max-width:24rem}
}

/* ======================= LESSONS LIST / CHAPTER ======================= */
.chapters{display:grid;grid-template-columns:repeat(auto-fill,minmax(19rem,1fr));gap:1rem;list-style:none;padding:0;margin:0}
.chapters li>a{height:100%;border:1px solid var(--line);background:var(--surface);border-radius:var(--r);padding:1.15rem 1.25rem;display:flex;gap:1rem;align-items:flex-start;color:inherit;text-decoration:none;transition:border-color .15s,transform .15s}
.chapters li>a:hover{border-color:var(--purple);transform:translateY(-1px)}
.chapters li.open>a{border:2px solid var(--purple);background:var(--purple-soft)}
.chapters .num{font-family:var(--display);font-weight:600;font-size:1.6rem;color:var(--purple);min-width:2.2rem;font-variant-numeric:tabular-nums;line-height:1.2}
.chapters .t{display:block;font-weight:700;line-height:1.3}
.chapters .s{display:block;font-size:.92rem;color:var(--muted);line-height:1.45;margin-top:.2rem}
.chapters .tag{display:inline-block;margin-top:.5rem;font-size:.78rem;font-weight:800;letter-spacing:.06em;text-transform:uppercase;padding:.1rem .55rem;border-radius:999px;background:var(--slate-soft);color:var(--muted)}
.chapters .tag.free{background:var(--green-soft);color:var(--green)}
.chapters .tag.done{background:var(--navy-soft);color:var(--navy)}
.toc-list{list-style:none;margin:0;padding:0;border-top:1px solid var(--line)}
.toc-list a{display:grid;grid-template-columns:3.2rem minmax(0,1fr) auto;gap:1rem;align-items:baseline;padding:1rem .2rem;border-bottom:1px solid var(--line);color:var(--ink);text-decoration:none}
.toc-list a:hover .t{color:var(--purple)}
.toc-list .num{font-family:var(--display);font-weight:600;color:var(--purple);font-variant-numeric:tabular-nums}
.toc-list .t{font-weight:700}
.toc-list .d{display:block;color:var(--muted);font-size:.95rem;line-height:1.5;margin-top:.2rem}
.toc-list .ok{font-size:.8rem;font-weight:800;color:var(--green);background:var(--green-soft);border-radius:999px;padding:.1rem .55rem}

/* ======================= LESSON PLAYER ======================= */
.player{display:grid;grid-template-columns:17rem minmax(0,1fr);gap:clamp(2rem,5vw,4.5rem);padding-block:2.5rem 5rem}
.rail{position:sticky;top:calc(env(safe-area-inset-top,0px) + 6.5rem);align-self:start;display:grid;gap:1.25rem;min-width:0;max-height:calc(100vh - 8rem);overflow:auto}
.rail .pct{display:flex;align-items:center;gap:1rem}
.rail .pct>div:last-child{min-width:0}
.rail .pct b{display:block;font-family:var(--display);font-size:1.05rem;line-height:1.3}
.rail .pct span{font-size:.88rem;color:var(--muted)}
.ring{--p:0;width:64px;height:64px;border-radius:50%;background:conic-gradient(var(--green) calc(var(--p)*1%),var(--line) 0);display:grid;place-items:center;flex:none}
.ring span{width:50px;height:50px;border-radius:50%;background:var(--paper);display:grid;place-items:center;font-weight:700;font-size:.95rem;font-variant-numeric:tabular-nums;color:var(--ink)!important}
.toc{display:grid;gap:.15rem;list-style:none;padding:0;margin:0}
.toc a{width:100%;text-align:left;display:flex;gap:.7rem;align-items:flex-start;padding:.55rem .7rem;border-radius:10px;color:var(--muted);line-height:1.35;font-size:.95rem;text-decoration:none}
.toc a:hover{background:var(--surface);color:var(--ink)}
.toc a[aria-current="step"]{background:var(--purple-soft);color:var(--ink);font-weight:700}
.toc .dot{flex:none;width:1.5rem;height:1.5rem;border-radius:50%;border:2px solid var(--line);display:grid;place-items:center;font-size:.8rem;margin-top:.05rem;background:var(--surface);font-weight:700}
.toc .done .dot{background:var(--green);border-color:var(--green);color:var(--on-accent)}
.toc a[aria-current="step"] .dot{border-color:var(--purple)}
.stage{min-width:0;display:grid;gap:clamp(2.25rem,5vw,3.5rem)}
.stage>section{display:flex;flex-direction:column;gap:1.25rem;min-width:0}
.screen-top{display:grid;gap:1rem;padding-bottom:1.5rem;border-bottom:1px solid var(--line)}
.screen-top .kicker{display:flex;align-items:center;gap:.75rem;flex-wrap:wrap}
.screen-top .tn{font-family:var(--display);font-weight:600;font-size:1rem;background:var(--purple);color:var(--on-accent);border-radius:8px;padding:.15rem .55rem;font-variant-numeric:tabular-nums}
.screen-top h1{font-size:var(--s3)}
.sec-k{display:flex;align-items:center;gap:.6rem;font-size:.82rem;letter-spacing:.12em;text-transform:uppercase;font-weight:800;color:var(--c,var(--muted))}
.sec-k .n{flex:none;width:1.7rem;height:1.7rem;border-radius:50%;display:grid;place-items:center;background:var(--c);color:var(--on-accent);letter-spacing:0;font-size:.85rem}
.sec-k::after{content:"";flex:1;height:2px;border-radius:2px;background:color-mix(in srgb,var(--c,var(--muted)) 30%,transparent)}
.concept{background:var(--slate-soft);border-radius:var(--r);padding:clamp(1.1rem,2.5vw,1.6rem)}
.concept .blk-title{color:var(--slate)}
.clue{display:grid;gap:.5rem;padding:1rem 1.2rem;border-radius:var(--r);background:var(--clue-soft);border:1px solid color-mix(in srgb,var(--clue) 40%,var(--line));border-left:5px solid var(--clue);line-height:1.7}
.clue strong{color:color-mix(in srgb,var(--clue) 70%,var(--ink))}
.pt{display:flex;gap:.7rem;align-items:flex-start;border-left:4px solid var(--gold);background:var(--gold-soft);padding:.65rem .9rem;border-radius:0 10px 10px 0;line-height:1.55;font-size:.98rem}
.pt .tag{flex:none;font-size:.8rem;font-weight:800;letter-spacing:.08em;text-transform:uppercase;color:var(--gold);margin-top:.2rem;white-space:nowrap}
.pager{display:flex;justify-content:space-between;gap:1rem;flex-wrap:wrap;padding-top:2rem;border-top:1px solid var(--line)}
@media (max-width:900px){
  .player{grid-template-columns:minmax(0,1fr);gap:1.25rem;padding-top:1rem}
  .rail{position:static;gap:.75rem;max-height:none;overflow:visible}
  .rail .pct .ring{width:48px;height:48px}.rail .pct .ring span{width:38px;height:38px;font-size:.8rem}
  .toc{display:flex;overflow-x:auto;gap:.4rem;padding-bottom:.4rem;scrollbar-width:thin}
  .toc li{flex:none}
  .toc a{white-space:nowrap;border:1px solid var(--line);border-radius:999px;padding:.4rem .8rem;background:var(--surface)}
  .toc .full{display:none}
}
@media (min-width:901px){.toc .short{display:none}}

/* ======================= QUESTIONS ======================= */
.panel{background:var(--surface);border:1px solid var(--line);border-radius:18px;padding:clamp(1.25rem,3vw,1.75rem);display:flex;flex-direction:column;gap:1rem;box-shadow:var(--shadow);min-width:0}
.panel h3{font-family:var(--body);font-weight:700;font-size:var(--s1);line-height:1.45;letter-spacing:0}
.q-k{font-size:.8rem;letter-spacing:.1em;text-transform:uppercase;font-weight:800;color:var(--purple)}
.tag-from{font-size:.82rem;font-weight:700;color:var(--purple);letter-spacing:.04em}
.choices{display:grid;grid-template-columns:repeat(auto-fit,minmax(13rem,1fr));gap:.65rem}
.choice{width:100%;text-align:left;display:flex;gap:.85rem;align-items:center;min-height:56px;padding:.7rem 1rem;border-radius:12px;border:2px solid var(--line);background:var(--surface);cursor:pointer;transition:border-color .15s,background .15s;min-width:0;color:var(--ink)}
.choice b{flex:none;width:2rem;height:2rem;border-radius:50%;display:grid;place-items:center;background:var(--slate-soft);font-weight:700;font-size:.95rem}
.choice:hover{border-color:var(--blue)}
.choice.right{border-color:var(--green);background:var(--green-soft)}
.choice.right b{background:var(--green);color:var(--on-accent)}
.choice.wrong{border-color:var(--red);background:var(--red-soft)}
.choice.wrong b{background:var(--red);color:var(--on-accent)}
.numrow{display:flex;gap:.6rem;flex-wrap:wrap;align-items:center}
.numrow label{flex-basis:100%}
.numrow input{flex:1 1 9rem;min-width:0;max-width:16rem;min-height:52px;border-radius:12px;border:2px solid var(--line);background:var(--paper);color:var(--ink);padding:.5rem .9rem;font:inherit;font-size:1.15rem}
.numrow input:focus{border-color:var(--blue);outline:none}
.numrow .unit{color:var(--muted);font-weight:600}
.feedback:empty{display:none}
.feedback{border-left:5px solid var(--green);background:var(--green-soft);padding:.9rem 1.1rem;border-radius:0 12px 12px 0;line-height:1.6;animation:pop .25s ease-out}
.feedback.no{border-color:var(--red);background:var(--red-soft)}
@keyframes pop{from{transform:translateY(4px);opacity:.4}to{transform:none;opacity:1}}
.linkbtn{background:none;border:0;padding:0;min-height:44px;color:var(--gold);font-weight:700;cursor:pointer;text-decoration:underline;text-underline-offset:3px;align-self:flex-start}
.hint{border-left:5px solid var(--clue);background:var(--clue-soft);border-radius:0 12px 12px 0;padding:.8rem 1rem;display:grid;gap:.5rem;animation:pop .25s ease-out;line-height:1.6}
.hint .hs-k{font-size:.78rem;font-weight:800;letter-spacing:.1em;text-transform:uppercase;color:color-mix(in srgb,var(--clue) 75%,var(--ink))}
.hint .pt{background:transparent;border:0;padding:0}
[data-clue]{border-left:5px solid var(--clue);background:var(--clue-soft);border-radius:0 12px 12px 0;padding:.7rem 1rem}

/* ======================= PRACTICE / CARDS / FINAL ======================= */
.chips{display:flex;flex-wrap:wrap;gap:.45rem}
.chip{min-height:44px;display:inline-flex;align-items:center;padding:.35rem .95rem;border-radius:999px;border:2px solid var(--line);background:var(--surface);color:var(--ink);font-weight:700;text-decoration:none;font-size:.95rem}
.chip:hover{border-color:var(--navy)}
.chip[aria-pressed="true"]{border-color:var(--navy);background:var(--navy);color:var(--on-accent)}
.set{display:grid;gap:1rem}
.set>h2{font-size:var(--s2);color:var(--purple)}
.flash{perspective:1400px;cursor:pointer;border:none;background:none;padding:0;text-align:left;width:100%;max-width:46rem}
.flash-inner{position:relative;width:100%;transition:transform .5s;transform-style:preserve-3d;display:grid}
.flash.flipped .flash-inner{transform:rotateY(180deg)}
.face{grid-area:1/1;position:relative;min-height:18rem;min-width:0;-webkit-backface-visibility:hidden;backface-visibility:hidden;border-radius:22px;padding:clamp(1.5rem,4vw,2.25rem);display:grid;align-content:center;gap:1rem;border:2px solid var(--line);background:var(--surface);overflow-wrap:anywhere;box-shadow:var(--shadow);color:var(--ink)}
.face.back{transform:rotateY(180deg);border-color:var(--gold);background:var(--gold-soft)}
.face .tag{font-size:.8rem;letter-spacing:.12em;text-transform:uppercase;font-weight:700;color:var(--purple)}
.face.back .tag{color:var(--gold)}
.face .ft{font-family:var(--display);font-size:var(--s2);line-height:1.35;font-weight:600}
.face.back .ft{font-family:var(--body);font-size:var(--s1);font-weight:500;line-height:1.55}
.face .flip-h{font-size:.88rem;color:var(--muted)}
.meter{display:flex;justify-content:space-between;gap:1rem;align-items:center;font-size:.95rem;color:var(--muted);font-variant-numeric:tabular-nums;flex-wrap:wrap;max-width:46rem}
.track{height:10px;border-radius:999px;background:var(--line);overflow:hidden;flex:1;min-width:8rem}
.track i{display:block;height:100%;background:var(--green);width:0;transition:width .3s}

/* ======================= MY SCHOOL / GET ALL ======================= */
.ms-form{display:grid;gap:1rem;max-width:34rem;background:var(--surface);border:1px solid var(--line);border-radius:18px;padding:clamp(1.25rem,3vw,1.75rem);box-shadow:var(--shadow)}
.ms-form label{display:grid;gap:.35rem;font-weight:700}
.ms-form input,.ms-form select{min-height:52px;border-radius:12px;border:2px solid var(--line);background:var(--paper);color:var(--ink);padding:.5rem .9rem;font:inherit}
.ms-form input:focus,.ms-form select:focus{border-color:var(--navy);outline:none}
.ms-saved{color:var(--green);font-weight:700}

/* ======================= RUBY (topic finder) ======================= */
#guide{position:fixed;right:max(18px,env(safe-area-inset-right,0px));bottom:max(18px,env(safe-area-inset-bottom,0px));z-index:31}
#guide-open{display:flex;align-items:center;gap:.55rem;padding:.3rem 1.1rem .3rem .35rem;border-radius:999px;border:2px solid var(--navy);background:var(--surface);color:var(--navy);font-weight:700;box-shadow:var(--shadow);cursor:pointer;line-height:1.2;text-align:left;transition:opacity .2s}
#guide-open svg{width:54px;height:54px;flex:none}
#guide-open .g-long{font-size:.95rem}
#guide-open .g-short{display:none}
body.guide-off #guide-open{visibility:hidden;opacity:0;pointer-events:none}
#guide-panel{position:absolute;right:0;bottom:0;width:23rem;max-width:calc(100vw - 24px);max-height:min(36rem,calc(100vh - 110px));overflow:auto;background:var(--surface);border:1px solid var(--line);border-radius:18px;box-shadow:var(--shadow);padding:1rem;display:grid;gap:.75rem;align-content:start}
#guide .g-head{display:flex;align-items:center;gap:.6rem;font-family:var(--display);font-size:1.12rem;color:var(--navy);line-height:1.3}
#guide .g-head svg{width:56px;height:56px;flex:none}
#guide .g-head b{flex:1}
#guide-close{border:0;background:none;font-size:1.6rem;line-height:1;color:var(--muted);cursor:pointer;padding:.1rem .3rem;min-width:44px;min-height:44px}
#guide-q{width:100%;min-height:48px;padding:.6rem .85rem;border:2px solid var(--line);border-radius:12px;font:inherit;background:var(--paper);color:var(--ink)}
#guide-q:focus{outline:none;border-color:var(--navy)}
#guide .g-label{font-size:.78rem;letter-spacing:.1em;text-transform:uppercase;color:var(--muted);font-weight:700}
#guide .g-chips{display:flex;flex-wrap:wrap;gap:.4rem}
#guide .g-chips button{border:1px solid var(--line);background:var(--paper);border-radius:999px;padding:.35rem .75rem;font-size:.9rem;color:var(--navy);cursor:pointer;min-height:40px;font-weight:600}
#guide .g-results{list-style:none;margin:0;padding:0;display:grid;gap:.45rem}
#guide .g-results a{display:grid;gap:.1rem;border:1px solid var(--line);background:var(--paper);border-radius:12px;padding:.6rem .75rem;color:var(--ink);text-decoration:none;line-height:1.35}
#guide .g-results a:hover{border-color:var(--navy)}
#guide .g-where{font-size:.8rem;color:var(--muted)}
#guide .g-tag{font-size:.78rem;font-weight:700;color:var(--gold)}
#guide .g-tag.open{color:var(--green)}
#guide .g-none{color:var(--muted);font-size:.95rem}
@media (max-width:640px){
  #guide{right:12px;bottom:12px}
  #guide-open .g-long{display:none}#guide-open .g-short{display:inline}
  #guide-open{padding:.25rem 1rem .25rem .3rem}#guide-open svg{width:46px;height:46px}
  #guide-panel{position:fixed;left:12px;right:12px;bottom:12px;width:auto}
}
@media (prefers-reduced-motion: reduce){*{transition:none!important;animation:none!important;scroll-behavior:auto!important}.f-pause{display:none}}
/* QA sweep fixes */
.screen-top + .toc-list{border-top:0}
.screen-top .tn{font-family:var(--body);font-weight:700;font-size:.92rem;letter-spacing:.02em;padding:.2rem .65rem}
@media (max-width:640px){main{padding-bottom:4.5rem}}
/* Ruby tucks down to just the dog while reading */
body.tuck #guide-open .g-long,body.tuck #guide-open .g-short{display:none}
body.tuck #guide-open{padding:.25rem;gap:0}
body.tuck #guide-open:hover .g-long,body.tuck #guide-open:focus-visible .g-long{display:inline}
@media (max-width:640px){.pt{flex-direction:column;gap:.15rem}.pt .tag{white-space:normal;margin-top:0}}
/* answer choices: even grids (2×2 for four, three across for three), one column on phones */
.choices{grid-template-columns:repeat(2,minmax(0,1fr))}
.choices:has(> :nth-child(3):last-child){grid-template-columns:repeat(3,minmax(0,1fr))}
@media (max-width:640px){.choices,.choices:has(> :nth-child(3):last-child){grid-template-columns:minmax(0,1fr)}}

/* flashcard steps (Chemistry I format: Spot the clue → Explain the clue → Break it down) */
.card-steps{display:grid;gap:.6rem;max-width:46rem}
.card-steps:empty{display:none}
.cs-k{font-size:.8rem;letter-spacing:.12em;text-transform:uppercase;font-weight:800;color:var(--muted);margin-top:.4rem}
.cs{--c:var(--clue);--cs:var(--clue-soft);border:2px solid color-mix(in srgb,var(--c) 45%,var(--line));border-radius:var(--r);background:var(--surface);overflow:hidden}
.cs.why-step{--c:var(--navy);--cs:var(--navy-soft)}
.cs.solve-step{--c:var(--green);--cs:var(--green-soft)}
.cs[open]{background:var(--cs)}
.cs summary{list-style:none;cursor:pointer;display:flex;align-items:center;gap:.7rem;min-height:56px;padding:.6rem 1rem;font-weight:700;color:color-mix(in srgb,var(--c) 75%,var(--ink))}
.cs summary::-webkit-details-marker{display:none}
.cs summary::after{content:"+";margin-left:auto;font-size:1.3rem;line-height:1;color:var(--c)}
.cs[open] summary::after{content:"−"}
.cs-n{flex:none;width:1.8rem;height:1.8rem;border-radius:50%;display:grid;place-items:center;background:var(--c);color:var(--on-accent);font-size:.9rem;font-weight:800}
.cs-b{padding:0 1.1rem 1.1rem 3.5rem;display:grid;gap:.8rem;line-height:1.65;animation:pop .25s ease-out}
.cs-list{margin:0;padding:0;list-style:none;counter-reset:cl;display:grid;gap:.5rem}
.cs-list li{counter-increment:cl;display:grid;grid-template-columns:1.7rem minmax(0,1fr);gap:.5rem;line-height:1.6}
.cs-list li::before{content:counter(cl);width:1.5rem;height:1.5rem;border-radius:50%;display:grid;place-items:center;background:var(--surface);border:2px solid var(--green);color:var(--green);font-size:.8rem;font-weight:800;margin-top:.15rem}
.rate{display:grid;gap:.4rem}
.rate-row{display:flex;flex-wrap:wrap;gap:.5rem}
.rate-b{min-height:48px;padding:.45rem 1rem;border-radius:999px;border:2px solid var(--line);background:var(--surface);color:var(--ink);font-weight:700;font-size:.95rem;cursor:pointer}
.rate-b.own{--c:var(--green)}.rate-b.help{--c:var(--gold)}.rate-b.again{--c:var(--red)}
.rate-b:hover{border-color:var(--c)}
.rate-b[aria-pressed="true"]{border-color:var(--c);background:var(--c);color:var(--on-accent)}
.rate-go{font-size:.98rem}
.rate-go a{font-weight:700;color:var(--navy)}
#card-tally{font-size:.9rem}.t-own{color:var(--green);font-weight:700}.t-help{color:var(--gold);font-weight:700}
.card-nav{margin-top:.4rem}
@media (max-width:560px){.cs-b{padding-left:1rem}.rate-row{display:grid}.rate-b{width:100%}}