:root{
  --bg:#fbfbfd;--card:#fff;--ink:#1d1d1f;--muted:#6e6e73;--line:#e5e5ea;--soft:#f2f2f5;
  --acc:#0f6b52;--acc-d:#0b5441;--acc-s:#e7f2ee;--bad:#c4271b;--bad-s:#fdeceb;--ok:#0f6b52;
  --r:14px;--sh:0 1px 2px rgba(0,0,0,.04),0 8px 28px rgba(0,0,0,.06);
}
*{box-sizing:border-box;margin:0}
html{color-scheme:light}
body{font:400 16px/1.5 Inter,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;background:var(--bg);color:var(--ink);-webkit-font-smoothing:antialiased}
button,input,textarea,select{font:inherit;color:inherit}
button{cursor:pointer}
h1,h2,h3{letter-spacing:-.022em;line-height:1.12;font-weight:650;text-wrap:balance}
p,.lede,.sub,li{text-wrap:pretty}
a{color:var(--acc)}
:focus-visible{outline:3px solid rgba(15,107,82,.35);outline-offset:2px}
.wrap{max-width:1080px;margin:0 auto;padding:0 20px}

/* buttons */
.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;min-height:44px;padding:0 20px;border-radius:12px;border:1px solid var(--line);background:var(--card);font-weight:550;text-decoration:none;color:var(--ink);transition:background .15s,transform .1s}
.btn:hover{background:var(--soft)}
.btn:active{transform:scale(.98)}
.btn.pri{background:var(--acc);border-color:var(--acc);color:#fff}
.btn.pri:hover{background:var(--acc-d)}
.btn.sm{min-height:36px;padding:0 14px;font-size:14px}
.btn[disabled]{opacity:.5;pointer-events:none}
.btn.danger{color:var(--bad)}

/* top bar (landing) */
.top{position:sticky;top:0;z-index:20;background:rgba(251,251,253,.85);backdrop-filter:saturate(180%) blur(18px);border-bottom:1px solid var(--line)}
.top .wrap{display:flex;align-items:center;justify-content:space-between;height:60px}
.logo{display:flex;align-items:center;gap:10px;font-weight:650;letter-spacing:-.01em;text-decoration:none;color:var(--ink)}
.logo img{width:30px;height:30px;border-radius:8px}
.top nav{display:flex;align-items:center;gap:6px}
.top nav a.t{padding:8px 12px;color:var(--muted);text-decoration:none;font-size:15px;border-radius:8px}
.top nav a.t:hover{color:var(--ink)}

/* hero */
.hero{padding:72px 0 56px;display:grid;grid-template-columns:1.05fr .95fr;gap:56px;align-items:center}
.hero h1{font-size:clamp(40px,6vw,64px)}
.hero h1 em{font-style:normal;color:var(--acc)}
.lede{font-size:19px;line-height:1.55;color:#515154;margin:20px 0 28px;max-width:30em}
.cta{display:flex;gap:12px;flex-wrap:wrap}
.fine{font-size:13px;color:var(--muted);margin-top:14px}

/* demo stack in hero */
.demo{display:flex;flex-direction:column;gap:14px}
.demo .c{background:var(--card);border:1px solid var(--line);border-radius:18px;box-shadow:var(--sh);padding:20px}
.demo .c1{width:84%}
.demo .c2{width:84%;align-self:flex-end}
.demo .c3{width:78%;margin-left:6%}
.tag{font-size:12px;font-weight:600;letter-spacing:.06em;text-transform:uppercase;color:var(--acc)}
.demo h4{font-size:17px;margin:8px 0 6px;letter-spacing:-.01em}
.demo p{font-size:14.5px;color:var(--muted)}
.opt{display:flex;align-items:center;gap:10px;padding:9px 12px;border:1px solid var(--line);border-radius:10px;font-size:14px;margin-top:8px}
.opt.right{border-color:var(--acc);background:var(--acc-s)}
.opt i{width:18px;height:18px;border-radius:50%;border:1.5px solid var(--line);flex:none}
.opt.right i{background:var(--acc);border-color:var(--acc)}

/* sections */
.sec{padding:80px 0;border-top:1px solid var(--line)}
.sec h2{font-size:clamp(30px,4vw,42px);max-width:16em}
.sec .sub{color:var(--muted);font-size:18px;margin:14px 0 40px;max-width:34em}
.steps{display:grid;grid-template-columns:repeat(3,1fr);gap:40px}
.steps b{display:grid;place-items:center;width:32px;height:32px;border-radius:50%;background:var(--acc-s);font-size:14px;color:var(--acc);margin-bottom:16px}
.steps h3{font-size:21px;margin-bottom:8px}
.steps p{color:var(--muted)}
.tools{display:grid;grid-template-columns:repeat(2,1fr);gap:0;border:1px solid var(--line);border-radius:18px;overflow:hidden;background:var(--card)}
.tools div{padding:28px;border-right:1px solid var(--line);border-bottom:1px solid var(--line)}
.tools div:nth-child(2n){border-right:0}
.tools div:nth-last-child(-n+2){border-bottom:0}
.tools h3{font-size:19px;margin-bottom:6px}
.tools p{color:var(--muted);font-size:15.5px}

/* plans */
.plans{display:grid;grid-template-columns:repeat(3,1fr);gap:16px}
.plan{background:var(--card);border:1px solid var(--line);border-radius:18px;padding:28px;display:flex;flex-direction:column}
.plan.hot{border:2px solid var(--acc);box-shadow:var(--sh)}
.plan h3{font-size:20px}
.price{font-size:40px;font-weight:650;letter-spacing:-.03em;margin:10px 0 2px}
.price small{font-size:15px;font-weight:450;color:var(--muted);letter-spacing:0}
.plan ul{list-style:none;padding:0;margin:18px 0 24px;flex:1}
.plan li{padding:7px 0 7px 26px;position:relative;font-size:15px;color:#3a3a3c}
.plan li:before{content:"";position:absolute;left:2px;top:13px;width:10px;height:6px;border-left:2px solid var(--acc);border-bottom:2px solid var(--acc);transform:rotate(-45deg)}
.plan .badge{font-size:12px;font-weight:600;color:var(--acc);margin-bottom:8px;letter-spacing:.04em;text-transform:uppercase;min-height:18px}
.band{margin:0 0 72px;background:var(--ink);color:#fff;border-radius:24px;padding:56px 32px;text-align:center}
.band h2{font-size:clamp(28px,4vw,38px);margin:0 auto 12px;max-width:14em}
.band p{color:#c7c7cc;margin-bottom:26px}
.band .btn{background:#fff;border-color:#fff;color:var(--ink)}
.band .btn:hover{background:#e8e8ed}
.foot{padding:40px 0;border-top:1px solid var(--line);color:var(--muted);font-size:14px}
.foot .wrap{display:flex;justify-content:space-between;flex-wrap:wrap;gap:12px}

/* auth */
.authpage{min-height:100vh;display:grid;place-items:center;padding:24px}
.authcard{width:100%;max-width:400px;background:var(--card);border:1px solid var(--line);border-radius:20px;padding:32px;box-shadow:var(--sh)}
.authcard h1{font-size:28px;margin:18px 0 6px}
.authcard .sub{color:var(--muted);margin-bottom:22px}
label.f{display:block;font-size:14px;font-weight:550;margin:14px 0 6px}
input.in,textarea.in,select.in{width:100%;min-height:44px;padding:10px 14px;border:1px solid #d2d2d7;border-radius:12px;background:#fff}
textarea.in{resize:vertical;line-height:1.5}
.chk{display:flex;gap:10px;align-items:flex-start;font-size:14px;color:var(--muted);margin:16px 0}
.chk input{width:20px;height:20px;margin-top:1px;accent-color:var(--acc);flex:none}
.msg{font-size:14px;margin-top:12px;color:var(--bad);min-height:20px}
.sw{margin-top:18px;text-align:center;font-size:14px;color:var(--muted)}
.sw button{background:none;border:0;color:var(--acc);font-weight:550;padding:4px}

/* app shell */
.shell{display:grid;grid-template-columns:240px 1fr;min-height:100vh}
.side{border-right:1px solid var(--line);padding:20px 14px;display:flex;flex-direction:column;gap:4px;position:sticky;top:0;height:100vh;background:var(--bg)}
.side .logo{padding:0 10px 18px}
.nav{display:flex;align-items:center;gap:12px;min-height:44px;padding:0 12px;border-radius:10px;color:var(--ink);text-decoration:none;font-weight:500;font-size:15px}
.nav svg{width:20px;height:20px;stroke:currentColor;fill:none;stroke-width:1.7;stroke-linecap:round;stroke-linejoin:round;color:var(--muted)}
.nav:hover{background:var(--soft)}
.nav.on{background:var(--acc-s);color:var(--acc)}
.nav.on svg{color:var(--acc)}
.side .gap{flex:1}
.meter{padding:12px;border:1px solid var(--line);border-radius:12px;font-size:13px;color:var(--muted);background:var(--card)}
.meter b{color:var(--ink);font-weight:600}
.bar{height:6px;background:var(--soft);border-radius:3px;margin-top:8px;overflow:hidden}
.bar i{display:block;height:100%;background:var(--acc);border-radius:3px;transition:width .4s}
.main{padding:36px 40px 80px;max-width:860px;width:100%}
.main h1{font-size:30px;margin-bottom:6px}
.main .sub{color:var(--muted);margin-bottom:26px}
.panel{background:var(--card);border:1px solid var(--line);border-radius:var(--r);padding:20px}
.row{display:flex;gap:12px;align-items:center;flex-wrap:wrap}
.seg{display:inline-flex;background:var(--soft);border-radius:10px;padding:3px}
.seg button{border:0;background:none;min-height:34px;padding:0 14px;border-radius:8px;font-size:14px;font-weight:550;color:var(--muted)}
.seg button.on{background:#fff;color:var(--ink);box-shadow:0 1px 3px rgba(0,0,0,.12)}

/* chat */
.chat{display:flex;flex-direction:column;gap:14px;margin:20px 0;min-height:120px}
.bub{max-width:88%;padding:12px 16px;border-radius:16px;line-height:1.55}
.bub.me{align-self:flex-end;background:var(--acc);color:#fff;border-bottom-right-radius:5px}
.bub.ai{align-self:flex-start;background:var(--card);border:1px solid var(--line);border-bottom-left-radius:5px}
.bub p{margin:0 0 .6em}.bub p:last-child{margin:0}
.bub ul,.bub ol{margin:.3em 0 .6em 1.2em}
.bub h4{font-size:16px;margin:.7em 0 .3em}
.bub code{background:var(--soft);padding:1px 6px;border-radius:5px;font-size:.92em}
.empty{color:var(--muted);text-align:center;padding:40px 10px}
.chips{display:flex;gap:8px;flex-wrap:wrap;margin-top:14px}
.chip{border:1px solid var(--line);background:var(--card);border-radius:10px;min-height:40px;padding:0 14px;font-size:14px}
.chip:hover{background:var(--soft)}
.compose{display:flex;gap:10px;align-items:flex-end;position:sticky;bottom:0;background:var(--bg);padding:12px 0}
.compose textarea{flex:1;min-height:48px;max-height:160px}
.dots span{display:inline-block;width:7px;height:7px;border-radius:50%;background:var(--muted);margin:0 2px;animation:b 1s infinite}
.dots span:nth-child(2){animation-delay:.15s}.dots span:nth-child(3){animation-delay:.3s}
@keyframes b{0%,60%,100%{opacity:.25}30%{opacity:1}}

/* flashcards */
.fc{perspective:1200px;margin:22px 0 14px}
.fc button.card{display:block;width:100%;height:280px;border:0;background:none;padding:0;position:relative;transform-style:preserve-3d;transition:transform .5s cubic-bezier(.2,.8,.2,1)}
.fc.flip button.card{transform:rotateY(180deg)}
.face{position:absolute;inset:0;backface-visibility:hidden;background:var(--card);border:1px solid var(--line);border-radius:20px;box-shadow:var(--sh);display:flex;flex-direction:column;align-items:center;justify-content:center;padding:32px;text-align:center;font-size:22px;font-weight:550;letter-spacing:-.01em}
.face small{position:absolute;top:18px;font-size:12px;letter-spacing:.06em;text-transform:uppercase;color:var(--acc);font-weight:600}
.face.back{transform:rotateY(180deg);background:var(--acc-s);border-color:#cfe5dc;font-weight:450;font-size:19px}
.prog{height:4px;background:var(--soft);border-radius:2px;overflow:hidden;margin-bottom:6px}
.prog i{display:block;height:100%;background:var(--acc);transition:width .3s}
.ctr{display:flex;justify-content:space-between;align-items:center;margin-top:16px;gap:10px}
.hint{font-size:13px;color:var(--muted);text-align:center}

/* quiz */
.q h3{font-size:21px;margin:6px 0 18px;line-height:1.3}
.ans{display:flex;gap:12px;align-items:center;width:100%;text-align:left;min-height:52px;padding:10px 16px;margin-bottom:10px;border:1px solid var(--line);border-radius:12px;background:var(--card);font-size:16px}
.ans:hover{background:var(--soft)}
.ans b{width:26px;height:26px;border-radius:50%;border:1.5px solid var(--line);display:grid;place-items:center;font-size:12px;flex:none;color:var(--muted)}
.ans.right{border-color:var(--ok);background:var(--acc-s)}
.ans.right b{background:var(--ok);border-color:var(--ok);color:#fff}
.ans.wrong{border-color:var(--bad);background:var(--bad-s)}
.ans.wrong b{background:var(--bad);border-color:var(--bad);color:#fff}
.why{background:var(--soft);border-radius:12px;padding:12px 16px;font-size:15px;margin:6px 0 14px}
.score{font-size:56px;font-weight:650;letter-spacing:-.04em;text-align:center;margin:10px 0}

/* summary */
.terms{display:grid;gap:0;margin-top:14px}
.terms div{padding:12px 0;border-top:1px solid var(--line)}
.terms b{display:block}
.terms span{color:var(--muted);font-size:15px}

/* library & account */
.list{display:grid;gap:10px}
.item{display:flex;justify-content:space-between;align-items:center;gap:12px;padding:14px 18px;background:var(--card);border:1px solid var(--line);border-radius:12px}
.item small{color:var(--muted);display:block}
.cur{font-size:13px;color:var(--acc);font-weight:600}
.toast{position:fixed;left:50%;bottom:90px;transform:translateX(-50%);background:var(--ink);color:#fff;padding:12px 18px;border-radius:12px;font-size:14px;z-index:50;max-width:90vw}

/* mobile */
@media(max-width:820px){
  .hero{grid-template-columns:1fr;padding:44px 0 24px;gap:36px}
    .steps,.plans{grid-template-columns:1fr}
  .tools{grid-template-columns:1fr}
  .tools div{border-right:0!important;border-bottom:1px solid var(--line)!important}
  .tools div:last-child{border-bottom:0!important}
  .shell{grid-template-columns:1fr}
  .side{position:fixed;bottom:0;left:0;right:0;top:auto;height:auto;flex-direction:row;padding:6px 6px calc(6px + env(safe-area-inset-bottom));border-right:0;border-top:1px solid var(--line);background:rgba(251,251,253,.92);backdrop-filter:blur(18px);z-index:30;justify-content:space-around}
  .side .logo,.side .gap,.side .meter{display:none}
  .nav{flex-direction:column;gap:2px;min-height:48px;padding:4px 8px;font-size:11px;flex:1;justify-content:center}
  .main{padding:22px 16px 110px}
  .main h1{font-size:26px}
  .top nav a.t{display:none}
  .face{font-size:19px}
  .bub{max-width:94%}
}
@media(prefers-reduced-motion:reduce){*{transition:none!important;animation:none!important}}

/* progress + scan */
.h2{font-size:24px;margin:40px 0 14px}
.topic{padding:20px}
.topic .tn{display:block;font-size:18px;letter-spacing:-.01em}
.topic .st{display:block;font-size:14px;color:var(--muted);margin-top:2px}
.topic .sum{margin:14px 0 10px;font-size:15px;color:#3a3a3c}
.up{color:var(--ok)}.down{color:var(--bad)}
.atts{border-top:1px solid var(--line)}
.att{display:grid;grid-template-columns:62px 56px 1fr 46px;gap:12px;align-items:center;min-height:44px;font-size:14px;border-bottom:1px solid var(--line);list-style:none}
.att .d{color:var(--muted)}.att .k{color:var(--muted);font-size:13px}.att b{text-align:right;font-variant-numeric:tabular-nums}
.att .bar{display:block;height:8px;background:var(--soft);border-radius:4px;margin:0;overflow:hidden}
.att .bar i{display:block;height:100%;background:var(--acc);border-radius:4px}
details.att-d>summary{cursor:pointer}
details.att-d>summary::-webkit-details-marker{display:none}
details.att-d>summary .k::after{content:" ▸"}
details.att-d[open]>summary .k::after{content:" ▾"}
.fb,.fbp{font-size:15px}
.fb{padding:14px 4px 16px;border-bottom:1px solid var(--line);background:var(--bg)}
.fb h5,.fbp h5{font-size:13px;letter-spacing:.05em;text-transform:uppercase;color:var(--acc);margin:16px 0 6px}
.fb h5:first-child,.fbp h5:first-child{margin-top:0}
.fb ul,.fbp ul{margin:0 0 0 1.1em}.fb li,.fbp li{margin:4px 0}
.fb p,.fbp p{margin:0 0 8px}
.qrow{display:flex;gap:12px;padding:8px 0;border-top:1px solid var(--line)}
.qrow:first-child{border-top:0}
.qm{flex:none;min-width:40px;font-weight:600;font-variant-numeric:tabular-nums}
input.file{padding:8px 10px;min-height:48px}
input.file::file-selector-button{border:1px solid var(--line);background:var(--soft);border-radius:8px;padding:8px 14px;margin-right:12px;font:inherit;font-weight:550;cursor:pointer}
.pv{display:block;max-width:100%;max-height:300px;border-radius:12px;border:1px solid var(--line);margin-top:14px}
@media(max-width:820px){.att{grid-template-columns:52px 50px 1fr 42px;gap:8px}.h2{font-size:22px}}

.planstrip{display:flex;align-items:center;justify-content:space-between;gap:12px;padding:18px 20px}
.planstrip .cur{display:block;font-size:12px;font-weight:600;letter-spacing:.06em;color:var(--acc)}
.planstrip strong{display:block;font-size:20px;letter-spacing:-.01em;margin:2px 0}
.planstrip small{color:var(--muted);font-size:14px}
details.cmp{margin-top:12px}
details.cmp>summary{cursor:pointer;font-weight:550;color:var(--acc);min-height:44px;display:flex;align-items:center;list-style:none}
details.cmp>summary::-webkit-details-marker{display:none}
details.cmp>summary::after{content:" ▾";margin-left:6px}
details.cmp[open]>summary::after{content:" ▴"}

/* ---- mobile-first refinements ---- */
.mtop{display:none}
.nav.more{display:none}
.morerow{text-decoration:none;color:var(--ink);padding:16px 18px;min-height:76px;justify-content:flex-start;gap:14px}
.morerow:hover{background:var(--soft)}
.morerow .mi{width:44px;height:44px;border-radius:12px;background:var(--acc-s);display:grid;place-items:center;color:var(--acc);flex:none}
.morerow .mi svg{width:22px;height:22px;stroke:currentColor;fill:none;stroke-width:1.7;stroke-linecap:round;stroke-linejoin:round}
.morerow .mt{flex:1}
.morerow .mt strong{display:block;font-size:17px}
.morerow .mt small{font-size:14px}
.morerow .chev{font-size:26px;color:var(--muted);line-height:1}
@media(max-width:820px){
  html{-webkit-text-size-adjust:100%}
  body{font-size:17px;line-height:1.55}
  .wrap{padding:0 22px}
  .top .wrap{height:64px}
  .hero{padding:36px 0 20px}
  .lede{font-size:18px}
  .cta .btn{flex:1 1 100%}
  .sec{padding:60px 0}
  .sec .sub{font-size:17px}
  .steps{gap:32px}
  .tools div{padding:24px 22px}
  .plan{padding:26px 22px}
  .band{padding:44px 24px;border-radius:20px;margin-bottom:56px}
  .authcard{padding:30px 24px}
  .mtop{display:flex;align-items:center;justify-content:space-between;position:sticky;top:0;z-index:25;height:58px;padding:0 20px;background:rgba(251,251,253,.9);backdrop-filter:saturate(180%) blur(18px);-webkit-backdrop-filter:saturate(180%) blur(18px);border-bottom:1px solid var(--line)}
  .chip2{font-size:13px;color:var(--muted);text-decoration:none;border:1px solid var(--line);border-radius:10px;padding:0 12px;background:var(--card);min-height:38px;display:inline-flex;align-items:center;gap:4px}
  .chip2 span{color:var(--ink);font-weight:600}
  .shell{display:block}
  .side{padding:8px 10px calc(8px + env(safe-area-inset-bottom))}
  .nav.sec{display:none}
  .nav.more{display:flex}
  .nav{min-height:58px;font-size:12px;gap:4px;border-radius:12px}
  .nav svg{width:25px;height:25px}
  .main{padding:26px 20px calc(120px + env(safe-area-inset-bottom))}
  .main h1{font-size:32px;letter-spacing:-.025em}
  .main .sub{font-size:16.5px;margin-bottom:24px}
  .panel{padding:22px 20px;border-radius:16px}
  label.f{font-size:15px;margin:18px 0 8px}
  input.in,textarea.in,select.in{min-height:52px;font-size:17px;padding:12px 16px;border-radius:14px}
  .btn{min-height:52px;font-size:17px;border-radius:14px}
  .btn.sm{min-height:44px;font-size:15px}
  .seg button{min-height:42px;padding:0 20px;font-size:15px}
  .notesbar{flex-direction:column;align-items:stretch;gap:14px}
  .notesbar .row{flex-wrap:nowrap}
  .notesbar .row select{width:96px;flex:none}
  .notesbar .row .btn{flex:1}
  .compose{bottom:calc(80px + env(safe-area-inset-bottom));padding:10px 0}
  .compose textarea{min-height:52px}
  .bub{font-size:17px;padding:14px 18px}
  .chips{flex-direction:column}
  .chip{min-height:48px;text-align:left;font-size:15px;padding:0 16px}
  .face{font-size:21px;padding:28px}
  .fc button.card{height:300px}
  .ctr{gap:12px}
  .ctr .btn{flex:1}
  .ans{min-height:60px;padding:12px 16px;font-size:17px}
  .q h3{font-size:22px}
  .item{padding:16px 18px;flex-wrap:wrap}
  .topic{padding:20px 18px}
  .topic>.row{flex-direction:column;align-items:stretch!important;gap:14px}
  .topic>.row .row .btn{flex:1}
  .att{min-height:52px;font-size:15px}
  .planstrip{padding:20px}
  .toast{bottom:calc(100px + env(safe-area-inset-bottom))}
}
@media(max-width:360px){
  .wrap{padding:0 18px}
  .main{padding-left:16px;padding-right:16px}
  .main h1{font-size:28px}
  .nav{font-size:11px}
  .hero h1{font-size:36px}
}

.drop{display:flex;flex-direction:column;align-items:center;gap:6px;padding:30px 16px;border:1.5px dashed #c7c7cc;border-radius:16px;text-align:center;cursor:pointer;background:var(--bg);transition:background .15s,border-color .15s}
.drop:hover{background:var(--acc-s);border-color:var(--acc)}
.drop:focus-within{outline:3px solid rgba(15,107,82,.35);outline-offset:2px}
.drop svg{width:34px;height:34px;stroke:var(--acc);fill:none;stroke-width:1.6;stroke-linecap:round;stroke-linejoin:round;margin-bottom:4px}
.drop strong{font-size:17px}
.drop small{color:var(--muted);font-size:14px}
.vh{position:absolute;width:1px;height:1px;opacity:0;overflow:hidden}

#out{scroll-margin-top:76px}

.ctr .btn{white-space:nowrap;padding:0 14px}