/* ============================================================================
   StudyGraph demo - "bright study" theme (light, Alice-inspired)
   Fraunces (display) / Hanken Grotesk (body) / IBM Plex Mono (technical labels)
   Light, luminous look: near-white surfaces, soft pastel gradients,
   clean white cards with soft shadows, generous whitespace.
   ============================================================================ */
@import url('vendor/fonts.css');

:root{
  /* surfaces */
  --bg:#f6f8fe;          /* app background (near white, cool) */
  --bg-2:#eef2fc;
  --surface:#ffffff;     /* cards */
  --surface-2:#fbfcff;
  --surface-3:#eef1f8;   /* subtle chips / tracks */
  --line:rgba(28,42,80,.08);
  --line-2:rgba(28,42,80,.14);
  /* text */
  --text:#1b2436;        /* primary ink */
  --text-dim:#4d5875;    /* secondary */
  --text-faint:#8790a6;  /* tertiary / mono captions */
  /* accents (readable on light) */
  --teal:#0ea394;        /* states & resources + primary accent */
  --teal-deep:#0b8578;
  --gold:#c2870b;        /* operations (darkened amber for contrast) */
  --violet:#7c5cff;      /* principles & effects */
  --coral:#e15645;       /* algorithms */
  --indigo:#5b6cff;      /* soft brand blue for gradients */
  --teal-dim:rgba(14,163,148,.12);
  --focus:#5b6cff;
  --shadow:0 22px 50px -26px rgba(31,45,90,.30);
  --shadow-soft:0 12px 30px -18px rgba(31,45,90,.22);
  --serif:'Fraunces',Georgia,'Times New Roman',serif;
  --sans:'Hanken Grotesk',-apple-system,BlinkMacSystemFont,'Segoe UI',sans-serif;
  --mono:'IBM Plex Mono',ui-monospace,'SF Mono',Menlo,monospace;
}

*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{
  margin:0;background:var(--bg);color:var(--text);
  font-family:var(--sans);font-size:17px;line-height:1.6;
  -webkit-font-smoothing:antialiased;text-rendering:optimizeLegibility;
  background-image:
    radial-gradient(1000px 560px at 82% -8%, rgba(91,108,255,.14), transparent 60%),
    radial-gradient(820px 500px at 4% 2%, rgba(124,92,255,.12), transparent 58%),
    radial-gradient(680px 620px at 50% 118%, rgba(225,86,69,.06), transparent 60%);
  background-attachment:fixed;
}
/* faint dot grid texture (light) */
body::before{
  content:"";position:fixed;inset:0;z-index:0;pointer-events:none;opacity:.6;
  background-image:radial-gradient(rgba(28,42,80,.05) 1px, transparent 1px);
  background-size:26px 26px;mask-image:radial-gradient(120% 80% at 50% 0%, #000 40%, transparent 100%);
}
.wrap{max-width:1220px;margin:0 auto;padding:0 26px;position:relative;z-index:1}

a{color:inherit}
b,strong{font-weight:600;color:var(--text)}
em{font-style:normal;color:var(--teal);font-weight:600}
.ket{font-family:var(--mono);font-size:.92em;color:var(--teal-deep);background:var(--teal-dim);
  padding:1px 6px;border-radius:5px;white-space:nowrap}

/* ---------- top nav ---------- */
.nav{position:sticky;top:0;z-index:50;backdrop-filter:blur(14px);
  background:linear-gradient(to bottom, rgba(255,255,255,.92), rgba(255,255,255,.72));
  border-bottom:1px solid var(--line)}
.nav-in{display:flex;align-items:center;gap:20px;height:66px}
.brand{display:flex;align-items:center;gap:11px;font-weight:600;letter-spacing:-.02em}
.brand .mark{width:30px;height:30px;flex:none}
.brand .name{font-family:var(--serif);font-size:22px;font-weight:600;letter-spacing:-.01em}
.brand .name b{color:var(--teal);font-weight:600}
.brand .tag{font-family:var(--mono);font-size:10px;letter-spacing:.18em;text-transform:uppercase;
  color:var(--text-faint);border:1px solid var(--line-2);padding:3px 7px;border-radius:20px}
.nav-tabs{display:flex;gap:4px;margin-left:auto}
.tab{font:inherit;font-size:14.5px;font-weight:500;color:var(--text-dim);background:none;border:0;
  padding:9px 15px;border-radius:9px;cursor:pointer;transition:.18s;position:relative}
.tab:hover{color:var(--text);background:rgba(28,42,80,.05)}
.tab.active{color:#fff;background:var(--teal);font-weight:600;box-shadow:0 8px 18px -8px rgba(14,163,148,.6)}
.tab .mo{font-family:var(--mono);font-size:11px;opacity:.6;margin-right:7px}
.tab.active .mo{opacity:.85}

/* ---------- sections ---------- */
.view{display:none;animation:fade .4s ease both}
.view.on{display:block}
@keyframes fade{from{opacity:0;transform:translateY(8px)}to{opacity:1;transform:none}}

.eyebrow{font-family:var(--mono);font-size:12px;letter-spacing:.22em;text-transform:uppercase;
  color:var(--teal-deep);display:flex;align-items:center;gap:10px;margin:0 0 16px}
.eyebrow::before{content:"";width:26px;height:1px;background:var(--teal);opacity:.6}

/* ---------- hero (soft pastel banner) ---------- */
.hero{padding:60px 46px 40px;margin-top:24px;border-radius:30px;position:relative;overflow:hidden;
  background:
    radial-gradient(760px 420px at 88% -10%, rgba(91,108,255,.18), transparent 62%),
    radial-gradient(620px 420px at 6% 0%, rgba(124,92,255,.16), transparent 60%),
    linear-gradient(170deg, #eef2ff 0%, #f4f0ff 45%, #fdf1f0 100%);
  border:1px solid rgba(124,92,255,.16);
  box-shadow:0 30px 70px -40px rgba(91,108,255,.45)}
.hero h1{font-family:var(--serif);font-weight:500;font-size:clamp(38px,6vw,72px);line-height:1.02;
  letter-spacing:-.025em;margin:0 0 22px;max-width:16ch;color:#141b2e}
.hero h1 .u{color:var(--teal-deep);font-style:italic;font-weight:500}
.hero p.lead{font-size:clamp(17px,2.1vw,21px);color:var(--text-dim);max-width:60ch;margin:0 0 30px}
.hero p.lead b{color:var(--text)}
.hero-cta{display:flex;flex-wrap:wrap;gap:14px;align-items:center}
.btn{font:inherit;font-weight:600;font-size:15.5px;cursor:pointer;border-radius:11px;
  padding:13px 24px;border:1px solid transparent;transition:.18s;display:inline-flex;align-items:center;gap:9px}
.btn.primary{background:var(--teal);color:#ffffff;box-shadow:0 12px 26px -10px rgba(14,163,148,.65)}
.btn.primary:hover{transform:translateY(-2px);background:var(--teal-deep);box-shadow:0 18px 38px -12px rgba(14,163,148,.7)}
.btn.ghost{background:rgba(255,255,255,.7);border-color:var(--line-2);color:var(--text)}
.btn.ghost:hover{background:#fff;border-color:var(--teal)}

.hero-stats{display:flex;flex-wrap:wrap;gap:14px;margin-top:44px}
.stat{flex:1;min-width:150px;border:1px solid var(--line);border-radius:15px;padding:20px 22px;
  background:rgba(255,255,255,.86);box-shadow:var(--shadow-soft)}
.stat .n{font-family:var(--serif);font-size:40px;font-weight:600;line-height:1;letter-spacing:-.02em}
.stat .n.t{color:var(--teal)} .stat .n.g{color:var(--gold)} .stat .n.v{color:var(--violet)} .stat .n.c{color:var(--coral)}
.stat .l{font-size:13.5px;color:var(--text-dim);margin-top:9px;letter-spacing:.01em}

.compare{display:grid;grid-template-columns:1fr 1fr;gap:16px;margin-top:26px}
.compare .col{border:1px solid var(--line);border-radius:16px;padding:22px 24px;background:rgba(255,255,255,.9);box-shadow:var(--shadow-soft)}
.compare .col.us{border-color:rgba(14,163,148,.4);background:linear-gradient(160deg,rgba(14,163,148,.08),#ffffff)}
.compare h4{margin:0 0 12px;font-size:13px;font-family:var(--mono);letter-spacing:.14em;text-transform:uppercase;color:var(--text-faint)}
.compare .col.us h4{color:var(--teal-deep)}
.compare ul{margin:0;padding:0;list-style:none;display:flex;flex-direction:column;gap:10px}
.compare li{display:flex;gap:11px;font-size:15px;color:var(--text-dim);line-height:1.45}
.compare li b{color:var(--text);font-weight:600}
.compare .ic{flex:none;margin-top:2px}

/* ---------- map ---------- */
.section-head{display:flex;align-items:flex-end;justify-content:space-between;gap:24px;
  padding:46px 0 22px;flex-wrap:wrap}
.section-head h2{font-family:var(--serif);font-weight:500;font-size:clamp(28px,4vw,44px);
  letter-spacing:-.02em;margin:0;line-height:1.05;color:#141b2e}
.section-head p{margin:8px 0 0;color:var(--text-dim);max-width:54ch;font-size:16px}
.map-shell{position:relative;border:1px solid var(--line-2);border-radius:20px;overflow:hidden;
  background:radial-gradient(130% 130% at 50% 0%, #ffffff, #eef2fb);box-shadow:var(--shadow)}
#cy{width:100%;height:min(72vh,700px);display:block}
.map-toolbar{position:absolute;top:14px;left:14px;display:flex;gap:8px;flex-wrap:wrap;z-index:5}
.map-search{position:absolute;top:14px;right:14px;z-index:5}
.map-search input{font:inherit;font-size:14px;background:rgba(255,255,255,.92);color:var(--text);
  border:1px solid var(--line-2);border-radius:10px;padding:9px 14px;width:210px;outline:none;backdrop-filter:blur(6px);box-shadow:var(--shadow-soft)}
.map-search input::placeholder{color:var(--text-faint)}
.map-search input:focus{border-color:var(--teal)}
.mbtn{font:inherit;font-size:13px;font-weight:500;color:var(--text-dim);cursor:pointer;
  background:rgba(255,255,255,.9);border:1px solid var(--line-2);border-radius:10px;padding:8px 13px;
  backdrop-filter:blur(6px);transition:.15s;box-shadow:var(--shadow-soft)}
.mbtn:hover{color:var(--text);border-color:var(--teal)}
.legend{position:absolute;bottom:14px;left:14px;z-index:5;display:flex;flex-wrap:wrap;gap:7px 16px;
  background:rgba(255,255,255,.9);border:1px solid var(--line);border-radius:12px;padding:11px 15px;backdrop-filter:blur(6px);box-shadow:var(--shadow-soft)}
.legend .item{display:flex;align-items:center;gap:8px;font-size:12.5px;color:var(--text-dim)}
.legend .dot{width:11px;height:11px;border-radius:50%;box-shadow:0 0 0 1px rgba(28,42,80,.12) inset}
.map-hint{position:absolute;bottom:14px;right:14px;z-index:5;font-family:var(--mono);font-size:11px;
  letter-spacing:.05em;color:var(--text-faint);background:rgba(255,255,255,.85);border:1px solid var(--line);
  border-radius:20px;padding:7px 13px;backdrop-filter:blur(6px)}

/* ---------- concept drawer (opens from map + learn) ---------- */
.drawer-scrim{position:fixed;inset:0;z-index:60;background:rgba(20,27,46,.28);
  opacity:0;pointer-events:none;transition:.28s;backdrop-filter:blur(2px)}
.drawer-scrim.open{opacity:1;pointer-events:auto}
.drawer{position:fixed;top:0;right:0;height:100%;width:min(500px,92vw);z-index:61;
  background:linear-gradient(180deg,#ffffff,#f6f8fe);border-left:1px solid var(--line-2);
  box-shadow:-30px 0 80px -30px rgba(31,45,90,.35);transform:translateX(102%);transition:transform .32s cubic-bezier(.4,0,.1,1);
  display:flex;flex-direction:column}
.drawer.open{transform:none}
.drawer-head{padding:26px 28px 18px;border-bottom:1px solid var(--line)}
.drawer-cat{font-family:var(--mono);font-size:11px;letter-spacing:.16em;text-transform:uppercase;display:flex;align-items:center;gap:8px;margin-bottom:12px}
.drawer-cat .dot{width:9px;height:9px;border-radius:50%}
.drawer h3{font-family:var(--serif);font-weight:600;font-size:32px;letter-spacing:-.02em;margin:0;line-height:1.05;color:#141b2e}
.drawer-close{position:absolute;top:22px;right:22px;width:34px;height:34px;border-radius:9px;
  background:rgba(28,42,80,.05);border:1px solid var(--line-2);color:var(--text-dim);cursor:pointer;
  font-size:18px;line-height:1;transition:.15s}
.drawer-close:hover{color:var(--text);border-color:var(--teal)}
.drawer-body{padding:24px 28px 40px;overflow-y:auto;flex:1}
.drawer-body p{font-size:16px;line-height:1.68;color:var(--text-dim)}
.clink{color:var(--teal-deep);text-decoration:none;border-bottom:1px dashed rgba(14,163,148,.5);
  cursor:pointer;font-weight:600;transition:.15s;white-space:nowrap}
.clink:hover{background:var(--teal-dim);border-bottom-style:solid}
.rel-title{font-family:var(--mono);font-size:11px;letter-spacing:.16em;text-transform:uppercase;
  color:var(--text-faint);margin:30px 0 14px;display:flex;align-items:center;gap:10px}
.rel-title::after{content:"";flex:1;height:1px;background:var(--line)}
.rel{display:flex;flex-direction:column;gap:9px}
.rel a{display:flex;align-items:center;gap:11px;text-decoration:none;padding:11px 13px;border-radius:11px;
  border:1px solid var(--line);background:var(--surface-2);transition:.16s;cursor:pointer}
.rel a:hover{border-color:var(--line-2);background:#fff;transform:translateX(3px);box-shadow:var(--shadow-soft)}
.rel .verb{font-family:var(--mono);font-size:10.5px;letter-spacing:.06em;color:#fff;
  background:var(--teal);padding:3px 8px;border-radius:6px;flex:none;font-weight:500}
.rel .verb.out{background:var(--teal)} .rel .verb.in{background:#eef1f8;color:var(--teal-deep);border:1px solid var(--line-2)}
.rel .to{font-weight:600;color:var(--text)}
.rel .to small{display:block;font-weight:400;color:var(--text-faint);font-size:12.5px;margin-top:2px;font-family:var(--sans)}
.rel .arw{margin-left:auto;color:var(--text-faint)}

/* ---------- learn ---------- */
.learn-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(260px,1fr));gap:14px;padding-bottom:60px}
.ccard{border:1px solid var(--line);border-radius:16px;padding:20px 21px;background:var(--surface);
  cursor:pointer;transition:.18s;position:relative;overflow:hidden;box-shadow:var(--shadow-soft)}
.ccard::before{content:"";position:absolute;left:0;top:0;bottom:0;width:3px;background:var(--cc,var(--teal))}
.ccard:hover{transform:translateY(-4px);border-color:var(--line-2);box-shadow:var(--shadow)}
.ccard .cc-cat{font-family:var(--mono);font-size:10px;letter-spacing:.14em;text-transform:uppercase;color:var(--cc);margin-bottom:11px;filter:brightness(.82)}
.ccard h4{font-family:var(--serif);font-weight:600;font-size:22px;letter-spacing:-.01em;margin:0 0 9px;color:#141b2e}
.ccard p{margin:0;font-size:14px;color:var(--text-dim);line-height:1.5}
.ccard .go{margin-top:14px;font-size:13px;font-weight:600;color:var(--cc);display:flex;align-items:center;gap:7px;filter:brightness(.82)}

/* ---------- quiz ---------- */
.quiz-wrap{max-width:720px;margin:0 auto;padding-bottom:70px}
.qbar{height:6px;border-radius:6px;background:var(--surface-3);overflow:hidden;margin-bottom:26px}
.qbar i{display:block;height:100%;background:linear-gradient(90deg,var(--teal),var(--violet));transition:.4s;border-radius:6px}
.qmeta{display:flex;justify-content:space-between;font-family:var(--mono);font-size:12px;letter-spacing:.06em;color:var(--text-faint);margin-bottom:14px}
.qcard{border:1px solid var(--line-2);border-radius:20px;padding:34px 34px 30px;background:var(--surface);box-shadow:var(--shadow)}
.qcard h3{font-family:var(--serif);font-weight:500;font-size:26px;line-height:1.25;letter-spacing:-.01em;margin:0 0 24px;color:#141b2e}
.opts{display:flex;flex-direction:column;gap:11px}
.opt{font:inherit;font-size:16px;text-align:left;cursor:pointer;padding:15px 18px;border-radius:13px;
  border:1px solid var(--line-2);background:var(--surface-2);color:var(--text);transition:.15s;
  display:flex;align-items:center;gap:14px}
.opt:hover:not(:disabled){border-color:var(--teal);background:rgba(14,163,148,.06)}
.opt .key{font-family:var(--mono);font-size:13px;width:26px;height:26px;flex:none;border-radius:7px;
  display:grid;place-items:center;background:var(--surface-3);color:var(--text-dim);transition:.15s}
.opt.correct{border-color:var(--teal);background:rgba(14,163,148,.12)}
.opt.correct .key{background:var(--teal);color:#fff}
.opt.wrong{border-color:var(--coral);background:rgba(225,86,69,.1)}
.opt.wrong .key{background:var(--coral);color:#fff}
.opt:disabled{cursor:default}
.qfeedback{margin-top:22px;border-radius:14px;padding:18px 20px;border:1px solid var(--line);
  background:var(--surface-2);display:none}
.qfeedback.show{display:block;animation:fade .3s both}
.qfeedback .verdict{font-weight:600;display:flex;align-items:center;gap:9px;margin-bottom:8px}
.qfeedback .verdict.ok{color:var(--teal-deep)} .qfeedback .verdict.no{color:var(--coral)}
.qfeedback p{margin:0 0 12px;font-size:15px;color:var(--text-dim)}
.qfeedback .chips{display:flex;flex-wrap:wrap;gap:8px}
.chip{font-family:var(--mono);font-size:11.5px;color:var(--teal-deep);border:1px solid rgba(14,163,148,.35);
  background:var(--teal-dim);border-radius:20px;padding:5px 11px;cursor:pointer;transition:.15s;text-decoration:none}
.chip:hover{background:rgba(14,163,148,.22)}
.qnav{display:flex;justify-content:flex-end;margin-top:22px}
.quiz-done{text-align:center;padding:50px 20px}
.quiz-done .score{font-family:var(--serif);font-size:74px;font-weight:600;letter-spacing:-.03em;color:var(--teal);line-height:1}
.quiz-done h3{font-family:var(--serif);font-weight:500;font-size:28px;margin:10px 0 8px;color:#141b2e}
.quiz-done p{color:var(--text-dim);margin:0 0 26px}

/* ---------- flashcards ---------- */
.fc-wrap{max-width:640px;margin:0 auto;padding-bottom:70px}
.fc-meta{display:flex;justify-content:space-between;align-items:center;font-family:var(--mono);
  font-size:12px;letter-spacing:.05em;color:var(--text-faint);margin-bottom:16px}
.fc-boxes{display:flex;gap:6px}
.fc-boxes b{color:var(--text-dim);font-weight:500}
.flash{perspective:1600px;height:340px;margin-bottom:22px}
.flash-in{position:relative;width:100%;height:100%;transition:transform .6s cubic-bezier(.4,0,.15,1);
  transform-style:preserve-3d;cursor:pointer}
.flash.flip .flash-in{transform:rotateY(180deg)}
.flash-face{position:absolute;inset:0;backface-visibility:hidden;border-radius:22px;padding:38px;
  display:flex;flex-direction:column;justify-content:center;align-items:center;text-align:center;
  border:1px solid var(--line-2);box-shadow:var(--shadow)}
.flash-front{background:radial-gradient(130% 130% at 50% 0%,#ffffff,#eef2fb)}
.flash-back{background:radial-gradient(130% 130% at 50% 0%,rgba(14,163,148,.12),#f3fbf9);transform:rotateY(180deg)}
.flash-face .tagline{font-family:var(--mono);font-size:11px;letter-spacing:.18em;text-transform:uppercase;color:var(--text-faint);margin-bottom:20px}
.flash-front .q{font-family:var(--serif);font-weight:500;font-size:28px;line-height:1.25;letter-spacing:-.01em;color:#141b2e}
.flash-back .a{font-size:18px;line-height:1.55;color:var(--text-dim);max-width:44ch}
.flash-face .flip-hint{position:absolute;bottom:20px;font-size:12px;color:var(--text-faint);display:flex;align-items:center;gap:7px}
.fc-actions{display:grid;grid-template-columns:repeat(3,1fr);gap:11px}
.fc-btn{font:inherit;font-weight:600;font-size:15px;cursor:pointer;padding:15px;border-radius:13px;
  border:1px solid var(--line-2);background:var(--surface);color:var(--text);transition:.15s;display:flex;flex-direction:column;align-items:center;gap:3px;box-shadow:var(--shadow-soft)}
.fc-btn small{font-family:var(--mono);font-size:10.5px;font-weight:400;color:var(--text-faint)}
.fc-btn:hover{transform:translateY(-2px)}
.fc-btn.again:hover{border-color:var(--coral)} .fc-btn.again{color:var(--coral)}
.fc-btn.good:hover{border-color:var(--gold)} .fc-btn.good{color:var(--gold)}
.fc-btn.easy:hover{border-color:var(--teal)} .fc-btn.easy{color:var(--teal-deep)}
.fc-reveal{opacity:.45;pointer-events:none}
.fc-done{text-align:center;padding:44px 20px}
.fc-done .big{font-family:var(--serif);font-size:40px;color:var(--teal);margin-bottom:6px}

/* ---------- footer ---------- */
.footer{border-top:1px solid var(--line);margin-top:20px;padding:40px 0 60px;color:var(--text-dim);font-size:14px}
.footer h5{font-family:var(--mono);font-size:11px;letter-spacing:.16em;text-transform:uppercase;color:var(--text-faint);margin:0 0 14px}
.src-list{display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:6px 22px;margin:0;padding:0;list-style:none}
.src-list a{color:var(--text-dim);text-decoration:none;font-size:13.5px;display:flex;gap:9px;padding:5px 0;transition:.15s}
.src-list a:hover{color:var(--teal-deep)}
.src-list .n{font-family:var(--mono);color:var(--text-faint);flex:none}
.footer .fine{margin-top:26px;font-size:12.5px;color:var(--text-faint);border-top:1px solid var(--line);padding-top:20px;line-height:1.6}
.footer .fine b{color:var(--text-dim);font-weight:500}

/* ---------- screenshot helper (collapses hero so the graph sits near top) ---------- */
.shot-graph .hero{display:none}
.shot-graph .section-head{padding-top:26px}

/* ---------- responsive ---------- */
@media(max-width:760px){
  body{font-size:16px}
  .nav-in{gap:10px;height:60px}
  .brand .tag{display:none}
  .nav-tabs{gap:2px}
  .tab{padding:8px 11px;font-size:13.5px}
  .tab .mo{display:none}
  .compare{grid-template-columns:1fr}
  .hero{padding:38px 24px 20px}
  #cy{height:66vh}
  .legend{position:static;margin:12px;flex-direction:column;gap:8px}
  .map-search input{width:150px}
  .qcard{padding:24px 20px}
  .fc-actions{grid-template-columns:1fr}
}
@media(min-width:761px) and (max-width:1000px){
  .map-search input{width:150px}
}