/* Teach Me — app.css. © 2026 Verge Heights (aplusz.app). All rights reserved. */
@font-face{font-family:"Source Serif 4";src:url("/assets/fonts/source-serif-4-latin.woff2") format("woff2");font-weight:200 900;font-style:normal;font-display:swap}
@font-face{font-family:"Source Serif 4";src:url("/assets/fonts/source-serif-4-latin-italic.woff2") format("woff2");font-weight:200 900;font-style:italic;font-display:swap}
:root{--cap:760px;--r:12px;--rs:8px;--serif:"Source Serif 4",Georgia,"Times New Roman",serif}
[data-theme=paper]{--bg:#ffffff;--fg:#1a1a1a;--mu:#6b6b6b;--ln:#e6e6e6;--card:#f7f7f5;--ok:#2f7d4f;--no:#b3402e}
[data-theme=ink]{--bg:#141414;--fg:#ececec;--mu:#9a9a9a;--ln:#2c2c2c;--card:#1d1d1d;--ok:#6fcf97;--no:#f2876f}
[data-theme=sepia]{--bg:#f4ecd8;--fg:#4a3b2a;--mu:#80705a;--ln:#e2d6b9;--card:#efe4cb;--ok:#3f7a3a;--no:#a5442c}
[data-theme=mist]{--bg:#eef2f5;--fg:#24323d;--mu:#62717d;--ln:#d6dee5;--card:#e5ebf0;--ok:#2d7a5a;--no:#b0452f}
[data-theme=forest]{--bg:#1b2a22;--fg:#dfe9e1;--mu:#93a99a;--ln:#2f4338;--card:#22342a;--ok:#8fd6a4;--no:#f0937b}
*{box-sizing:border-box}
html,body{margin:0;background:var(--bg);color:var(--fg)}
body{font-family:var(--serif);font-size:18px;line-height:1.7;min-height:100svh;display:grid;grid-template-rows:auto 1fr auto;-webkit-text-size-adjust:100%;transition:background .25s,color .25s}
a{color:inherit;text-underline-offset:3px;text-decoration-thickness:1px}
button{font:inherit;color:inherit;background:none;border:0;cursor:pointer;border-radius:var(--rs)}
.top,main,.bottom{width:100%;max-width:var(--cap);margin:0 auto;padding-left:20px;padding-right:20px}
.top{position:sticky;top:0;z-index:14;background:var(--bg);display:grid;grid-template-columns:1fr minmax(0,auto) 1fr;gap:12px;align-items:center;padding-top:calc(14px + env(safe-area-inset-top));padding-bottom:6px}
.ico{width:40px;height:40px;display:inline-flex;align-items:center;justify-content:center;opacity:.6;border-radius:50%}
.ico:hover,.ico:focus-visible{opacity:1}
.ico svg,.hm svg{width:21px;height:21px;fill:none;stroke:currentColor;stroke-width:1.5;stroke-linecap:round;stroke-linejoin:round}
.addr{justify-self:center;font-size:14px;color:var(--mu);text-decoration:none;display:inline-flex;align-items:center;gap:6px;border-radius:var(--rs);padding:2px 6px;white-space:nowrap;overflow:hidden;text-overflow:ellipsis;max-width:100%}
.addr:hover{color:var(--fg)}
.hm svg{width:15px;height:15px}
main{display:flex;flex-direction:column}
.bottom{display:flex;flex-wrap:wrap;justify-content:center;gap:6px 26px;padding-top:10px;padding-bottom:calc(16px + env(safe-area-inset-bottom));font-size:14px}
.bottom button,.bottom a{color:var(--mu);text-decoration:none;padding:4px 2px}
.bottom button:hover,.bottom a:hover{color:var(--fg)}
.hero{flex:1;display:flex;flex-direction:column;align-items:center;justify-content:center;text-align:center;padding:4vh 0 10vh}
.hero h1{font-size:clamp(34px,7vw,46px);font-weight:500;margin:0 0 1.6rem;letter-spacing:-.01em}
.lead{color:var(--mu);margin:0 0 1rem}
.ask{position:relative;display:inline-block;max-width:100%}
.measure{position:absolute;visibility:hidden;white-space:pre;font:inherit;font-size:19px;left:0;top:0;pointer-events:none}
.q{font:inherit;font-size:19px;color:var(--fg);background:transparent;border:0;border-bottom:1px solid var(--fg);border-radius:0;padding:4px 0;text-align:left;outline:none;max-width:100%;min-width:2ch;resize:none;overflow:hidden;line-height:1.45;display:block;margin:0 auto;white-space:pre-wrap;word-wrap:break-word}
.q::placeholder{color:var(--mu);opacity:1}
.q:focus{border-bottom-width:1.5px}
.sugg{position:absolute;left:50%;transform:translateX(-50%);top:calc(100% + 8px);min-width:100%;max-width:min(560px,calc(100vw - 32px));margin:0;padding:6px;list-style:none;background:var(--bg);border:1px solid var(--ln);border-radius:var(--r);text-align:left;z-index:5}
.sugg li a{display:block;padding:7px 12px;border-radius:var(--rs);text-decoration:none;font-size:16px;line-height:1.35}
.sugg li a span{display:block;font-size:12px;color:var(--mu)}
.sugg li a:hover,.sugg li a[aria-selected=true]{background:var(--card)}
.bar{text-align:center;padding:18px 0 8px}
.results{padding:10px 0 30px}
.reslist{list-style:none;margin:0;padding:0}
.res{padding:14px 0;border-bottom:1px solid var(--ln)}
.res a{text-decoration:none;display:block}
.res .crumb{display:block;font-size:13px;color:var(--mu);line-height:1.4}
.res .rt{font-size:21px;line-height:1.35}
.res a:hover .rt{text-decoration:underline}
.res p{margin:4px 0 0;color:var(--mu);font-size:16px;line-height:1.5}
.write{margin-top:18px;text-align:center}
.linkish{color:var(--mu);text-decoration:underline;text-underline-offset:3px;padding:4px 6px}
.linkish:hover{color:var(--fg)}
.lesson,.plain{padding:22px 0 40px}
.lesson .crumb{font-size:13px;color:var(--mu);margin:0 0 6px}
.lesson .crumb a{text-decoration:none}.lesson .crumb a:hover{text-decoration:underline}
.lesson h1,.plain h1{font-size:clamp(28px,5.5vw,38px);font-weight:500;line-height:1.2;margin:0 0 18px}
.lesson h2,.plain h2{font-size:22px;font-weight:500;margin:34px 0 8px;line-height:1.3}
.intro{font-size:20px;color:var(--fg)}
.lesson p{margin:0 0 14px}
code{font-family:ui-monospace,Consolas,monospace;font-size:.86em;background:var(--card);padding:1px 6px;border-radius:6px}
.keys ul,.next ul,.deeper ul,.plain ul{padding-left:1.2em;margin:0}
.keys li,.next li{margin:4px 0}
.deeper ul{list-style:none;padding:0}
.deeper li{padding:6px 0;border-bottom:1px solid var(--ln)}
.deeper li span{display:block;font-size:15px;color:var(--mu);line-height:1.45}
.qz{margin:14px 0 22px}
.qq{margin:0 0 8px!important}
.opts{display:grid;gap:8px}
.opts button{text-align:left;border:1px solid var(--ln);border-radius:var(--r);padding:9px 14px;line-height:1.45}
.opts button:hover{background:var(--card)}
.opts button.ok{border-color:var(--ok);color:var(--ok)}
.opts button.no{border-color:var(--no);color:var(--no)}
.why{color:var(--mu);font-size:16px;margin-top:8px!important}
.pn{display:flex;justify-content:space-between;gap:16px;margin-top:36px;font-size:15px}
.pn a{text-decoration:none;color:var(--mu);border:1px solid var(--ln);border-radius:var(--r);padding:8px 14px;max-width:48%}
.pn a:hover{color:var(--fg)}
.preparing{color:var(--mu);display:flex;align-items:center;gap:10px}
.dots{display:inline-flex;gap:5px}
.dots i{width:7px;height:7px;border-radius:50%;background:currentColor;animation:b 1.2s infinite ease-in-out}
.dots i:nth-child(2){animation-delay:.15s}.dots i:nth-child(3){animation-delay:.3s}
@keyframes b{0%,80%,100%{opacity:.25;transform:translateY(0)}40%{opacity:1;transform:translateY(-3px)}}
.count{font-size:20px;margin-top:24px!important}
.note{color:var(--mu);font-size:15px}
.pop{position:fixed;z-index:20;background:var(--bg);color:var(--fg);border:1px solid var(--ln);border-radius:var(--r);padding:8px;width:max-content;max-width:calc(100vw - 24px);box-shadow:0 8px 28px rgba(0,0,0,.12)}
.pop ul{list-style:none;margin:0;padding:0}
.pop li a,.pop li button{display:block;width:100%;text-align:left;padding:7px 14px;text-decoration:none;font-size:16px;border-radius:var(--rs)}
.pop li a:hover,.pop li button:hover,.pop [aria-current=true]{background:var(--card)}
.find{font:inherit;font-size:15px;width:100%;min-width:160px;border:1px solid var(--ln);border-radius:var(--rs);padding:6px 10px;background:transparent;color:var(--fg);margin-bottom:6px;outline:none}
.pop-qr{text-align:center;padding:14px}
.pop-qr #qrBox svg{width:180px;height:180px;display:block;margin:0 auto;border-radius:var(--rs)}
.pop-qr p,.pop-install p{margin:8px 0 0;font-size:14px;color:var(--mu)}
.pop-install{max-width:min(340px,calc(100vw - 24px));padding:14px 16px;font-size:16px;line-height:1.5}
.pill{position:fixed;left:50%;transform:translateX(-50%);bottom:calc(58px + env(safe-area-inset-bottom));z-index:15;font-size:14px;padding:6px 16px;border:1px solid var(--ln);border-radius:999px;background:var(--bg);color:var(--fg)}
.pill:hover{background:var(--card)}
.toast{position:fixed;left:50%;bottom:calc(96px + env(safe-area-inset-bottom));transform:translateX(-50%);background:var(--fg);color:var(--bg);font-size:14px;padding:6px 14px;border-radius:999px;opacity:0;pointer-events:none;transition:opacity .2s;z-index:30}
.toast.on{opacity:1}
:focus-visible{outline:2px solid var(--mu);outline-offset:2px}
.q:focus,.q:focus-visible,.typed input:focus,.typed input:focus-visible,.find:focus,.find:focus-visible{outline:none;box-shadow:none}
@media (max-width:520px){body{font-size:17px}.res .rt{font-size:19px}.pn{flex-direction:column}.pn a{max-width:100%}}
@media (prefers-reduced-motion:reduce){*{animation:none!important;transition:none!important}}
/* ---------- the learning engine */
.plan details{border-bottom:1px solid var(--ln);padding:6px 0}
.plan summary{cursor:pointer;list-style:none;padding:4px 0}
.plan summary::-webkit-details-marker{display:none}
.plan summary::before{content:"+";display:inline-block;width:1.1em;color:var(--mu)}
.plan details[open] summary::before{content:"–"}
.plan ol{margin:6px 0 8px;padding-left:2.4em;font-size:16px;color:var(--mu)}
.engine-on #static{display:none}
.stage-h{font-size:13px;color:var(--mu);margin:0 0 4px}
.stage h2{font-size:24px;font-weight:500;margin:6px 0 14px;line-height:1.3}
.btn{display:inline-block;font-size:17px;padding:9px 26px;border:1px solid var(--fg);border-radius:999px;text-decoration:none;margin:6px 0}
.btn:hover{background:var(--card)}
.btn-row{display:flex;flex-wrap:wrap;gap:10px;align-items:center;margin-top:18px}
.levels{display:grid;gap:10px;margin-top:10px}
.levels button{text-align:left;border:1px solid var(--ln);border-radius:var(--r);padding:12px 16px;line-height:1.4}
.levels button:hover{background:var(--card)}
.levels small{display:block;color:var(--mu);font-size:14px}
.dotsrow{display:flex;gap:7px;margin:4px 0 16px}
.dotsrow i{width:10px;height:10px;border-radius:50%;border:1px solid var(--mu)}
.dotsrow i.ok{background:var(--ok);border-color:var(--ok)}
.dotsrow i.no{background:var(--no);border-color:var(--no)}
.dotsrow i.now{border-color:var(--fg);border-width:2px}
.qbox .qq{font-size:20px;margin:0 0 12px!important;line-height:1.45}
.typed{display:flex;gap:8px;flex-wrap:wrap}
.typed input{font:inherit;font-size:18px;flex:1;min-width:180px;border:0;border-bottom:1px solid var(--fg);background:transparent;color:var(--fg);padding:6px 2px;outline:none;border-radius:0}
.guess{font-size:14px;color:var(--mu);margin-top:10px;display:inline-flex;gap:6px;align-items:center;cursor:pointer;user-select:none}
.guess input{accent-color:var(--fg)}
.verdict{margin-top:12px!important;font-size:16px}
.verdict.ok{color:var(--ok)}.verdict.no{color:var(--no)}
.verdict span{color:var(--mu);display:block}
.quiet{color:var(--mu);font-size:15px}
.examples{list-style:none;padding:0;margin:8px 0 0}
.examples li{border-left:2px solid var(--ln);padding:4px 0 4px 14px;margin:10px 0;border-radius:0}
.examples .ex{font-size:19px}
.examples .nt{display:block;color:var(--mu);font-size:16px}
.hear{font-size:14px;color:var(--mu);border:1px solid var(--ln);border-radius:999px;padding:1px 10px;margin-left:8px;vertical-align:2px}
.hear:hover{color:var(--fg)}
.me{flex:1;display:flex;flex-direction:column;justify-content:center;text-align:center;padding:20px 0 70px}
.me h1{font-size:clamp(30px,6vw,40px);font-weight:500;margin:0}
.me .lvl{color:var(--mu);margin:4px 0 22px}
.me .links{display:flex;flex-wrap:wrap;justify-content:center;gap:6px 22px;margin-top:20px;font-size:15px}
.me .links button,.me .links a{color:var(--mu);text-decoration:none}
.me .links button:hover,.me .links a:hover{color:var(--fg)}
.me .panel{text-align:left;max-width:520px;margin:18px auto 0;border:1px solid var(--ln);border-radius:var(--r);padding:12px 16px;font-size:16px}
.me .panel ul{margin:0;padding-left:1.2em}
.me .others{margin-top:14px;font-size:15px;color:var(--mu)}
.code{font-family:ui-monospace,Consolas,monospace;font-size:22px;letter-spacing:.12em;user-select:all}
.prog{position:fixed;left:0;right:0;bottom:0;z-index:12;pointer-events:none}
.prog-t{height:3px;background:var(--ln)}
.prog-f{height:100%;background:var(--fg);width:0;transition:width .5s ease;border-radius:0 2px 2px 0}
.prog-l{position:absolute;bottom:7px;transform:translateX(-50%);font-size:12px;color:var(--mu);white-space:nowrap;transition:left .5s ease}
body.has-prog .bottom{padding-bottom:calc(30px + env(safe-area-inset-bottom))}
body.has-prog .pill{bottom:calc(76px + env(safe-area-inset-bottom))}
.cert{flex:1;display:flex;flex-direction:column;justify-content:center;text-align:center;padding:40px 0}
.cert-k{letter-spacing:.14em;font-size:13px;color:var(--mu);text-transform:uppercase}
.cert h1{font-size:clamp(34px,7vw,52px);font-weight:500;margin:10px 0}
.cert-t{font-size:20px}.cert-d,.cert-v{color:var(--mu)}
@media print{.top,.bottom,.pill,.prog,.cert-a,.toast{display:none!important}body{background:#fff;color:#000}.cert{min-height:90vh;border:1px solid #999;border-radius:12px;margin:20px}}
.tl{display:flex;align-items:center;gap:4px;min-width:0}.tr{display:flex;justify-content:flex-end}
.plan{font-size:13px;color:var(--mu);text-decoration:none;padding:2px 6px;border-radius:var(--rs);white-space:nowrap}
.plan:hover,.plan[aria-current=page]{color:var(--fg)}
#planLink{font-weight:700}
#subjList .pc{color:var(--mu);font-size:13px;margin-left:10px}
.pls{display:grid;gap:12px;margin-top:8px}
.pl{border:1px solid var(--ln);border-radius:var(--r);padding:6px 18px 10px}
.pl h2{margin:10px 0 2px!important}.pl p{margin:4px 0}
.pl.is-cur{border-color:var(--fg)}
.cur{font-size:14px;color:var(--fg)}
.given{border-left:2px solid var(--ln);padding:2px 0 2px 14px;color:var(--mu);font-size:16px;border-radius:0;white-space:pre-line}
.analogy{color:var(--mu);font-style:italic}
.steps{padding-left:1.4em}.steps li{margin:4px 0}
.diag{display:flex;flex-wrap:wrap;align-items:center;gap:6px 8px;margin:18px 0}
.diag span{border:1px solid var(--ln);border-radius:var(--r);padding:5px 12px;font-size:16px;line-height:1.3}
.diag span.again{border-style:dashed;color:var(--mu)}
.diag i{font-style:normal;color:var(--mu)}
textarea.ex{font:inherit;font-size:18px;width:100%;border:0;border-bottom:1px solid var(--fg);background:transparent;color:var(--fg);padding:6px 2px;resize:vertical;outline:none;border-radius:0;line-height:1.5}
/* the top bar stays in view on any scroll; on phones everything keeps its own space */
.addr .hm{margin-right:2px}
@media (max-width:480px){
  .top{gap:6px;padding-left:10px;padding-right:10px}
  .ico{width:34px;height:34px}
  .ico svg{width:19px;height:19px}
  .tl{gap:0}.tr{gap:0}
  .plan{font-size:12.5px;padding:2px 4px}
  .addr{font-size:12.5px;padding:2px 2px}
  .hm svg{width:13px;height:13px}
}
@media (max-width:360px){.addr{font-size:11.5px}}
.notice{border:1px solid var(--fg);border-radius:var(--r);padding:10px 18px;margin:16px 0 0;font-size:16px}
.notice p{margin:6px 0}
.signin{margin-top:28px}
.signin .typed{margin-top:10px}
.also a{color:#2f6fdb;text-decoration:none}
[data-theme=ink] .also a,[data-theme=forest] .also a{color:#7aa7ff}
.plans-h{display:flex;align-items:baseline;justify-content:space-between;gap:12px}
.plans-h .linkish{font-size:16px}
.signin{margin:6px 0 18px;border:1px solid var(--ln);border-radius:var(--r);padding:4px 18px 12px}
#siOpen{font-weight:700}
.pl h2{text-align:center}
@media (min-width:700px){.pls{grid-template-columns:repeat(3,minmax(0,1fr))}}
.pl .price{text-align:center;font-size:18px;margin:0 0 8px!important}
.pl .buy{text-align:center;margin-top:12px!important}
.store-play [data-buy],.store-play .pl .price{display:none!important}
/* the second-day install offer: centred, the page blurred behind it */
.gated .top,.gated main,.gated .bottom,.gated .prog,.gated .pill{filter:blur(6px);pointer-events:none;user-select:none}
.gate{position:fixed;inset:0;z-index:40;display:flex;align-items:center;justify-content:center;padding:20px;background:color-mix(in srgb,var(--bg) 45%,transparent)}
.gate-card{background:var(--bg);border:1px solid var(--ln);border-radius:16px;padding:8px 24px 18px;max-width:440px;width:100%;box-shadow:0 18px 50px rgba(0,0,0,.18)}
.gate-card h2{font-size:24px;font-weight:500;margin:14px 0 2px;text-align:center}
.gate-card>.quiet{text-align:center;margin:0 0 10px}
.gate-card ul{padding-left:1.1em;margin:0;font-size:16px;line-height:1.55}
.gate-card li{margin:6px 0}
.gate-card .btn-row{justify-content:center}
/* the line under the address: the engine, one tap from its paper */
.top{grid-template-rows:auto auto}
.tagline{grid-column:1/-1;grid-row:2;justify-self:center;font-size:12.5px;color:var(--mu);text-decoration:none;text-align:center;margin-top:-4px;padding:0 8px;border-radius:var(--rs)}
.tagline:hover{color:var(--fg);text-decoration:underline;text-underline-offset:3px}
.paper-k{letter-spacing:.14em;font-size:13px;color:var(--mu);text-transform:uppercase;margin:0}
.paper .lead{font-size:20px;color:var(--fg)}
@media (max-width:480px){.tagline{font-size:11.5px}}
/* language picker: always below its button, never taller than the screen; the list scrolls, the find box stays */
#langPop{display:flex;flex-direction:column;overflow:hidden;min-width:220px}
#langPop[hidden]{display:none}
#langPop .find{flex:none;margin-bottom:6px}
#langList{flex:1 1 auto;min-height:0;overflow-y:auto;overscroll-behavior:contain;-webkit-overflow-scrolling:touch;scrollbar-width:thin}
/* the install button on phones: its own row at the top of the footer, never over the links; on wide screens it floats */
.bottom .pill{position:static;transform:none;order:-1;margin:0 0 6px;color:var(--fg);font-size:15px;padding:8px 20px}
.bottom .brk{order:-1;flex-basis:100%;height:0}
.bottom .pill[hidden],.bottom .pill[hidden]+.brk{display:none}
@media (min-width:701px){.bottom .pill{position:fixed;left:50%;transform:translateX(-50%);bottom:calc(58px + env(safe-area-inset-bottom));margin:0;font-size:14px;padding:6px 16px}
 body.has-prog .bottom .pill{bottom:calc(76px + env(safe-area-inset-bottom))}.bottom .brk{display:none}}
/* ⚑ Report this lesson */
.rep{text-align:center;margin:26px 0 0;font-size:14px}
.rep .linkish{font-size:14px}
.rep-card{display:flex;flex-direction:column;gap:6px;padding-bottom:16px}
.rep-r{display:flex;gap:10px;align-items:center;font-size:16px;padding:6px 2px;cursor:pointer}
.rep-card textarea{font:inherit;font-size:16px;color:var(--fg);background:var(--card);border:1px solid var(--ln);border-radius:10px;padding:8px 10px;margin-top:6px;resize:vertical}
.rep-msg{min-height:1.4em;margin:4px 0 0;text-align:center}