:root{
  --bg:#0b1020;
  --card:#111933;
  --card-2:#171f3f;
  --text:#f7f8ff;
  --muted:#b9c0e4;
  --line:rgba(255,255,255,.12);
  --brand:#6f72ff;
  --brand-2:#12d6c5;
  --accent:#ffe66d;
  --danger:#ff6b8a;
  --success:#42e6a4;
  --shadow:0 24px 70px rgba(0,0,0,.35);
  --radius:26px;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{
  margin:0;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background:
    radial-gradient(circle at top left, rgba(111,114,255,.35), transparent 34rem),
    radial-gradient(circle at 90% 10%, rgba(18,214,197,.20), transparent 30rem),
    linear-gradient(180deg, #070b17 0%, var(--bg) 55%, #080b16 100%);
  color:var(--text);
}
a{color:inherit;text-decoration:none}
button{font:inherit}
.app-shell{min-height:100vh;overflow:hidden}
.hero{position:relative;padding:20px 16px 40px}
.hero-bg{
  position:absolute;inset:0;
  background-image:
    linear-gradient(rgba(255,255,255,.045) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,.045) 1px, transparent 1px);
  background-size:28px 28px;
  mask-image:linear-gradient(#000, transparent 82%);
  pointer-events:none;
}
.topbar{
  position:relative;z-index:2;display:flex;gap:10px;justify-content:center;
  padding:8px;margin:0 auto 18px;max-width:720px;border:1px solid var(--line);
  background:rgba(12,18,39,.72);backdrop-filter:blur(18px);border-radius:999px;
}
.nav-pill{padding:10px 14px;border-radius:999px;color:var(--muted);font-weight:700;font-size:.9rem}
.nav-pill:hover{background:rgba(255,255,255,.08);color:var(--text)}
.hero-card{
  position:relative;z-index:1;max-width:920px;margin:0 auto;padding:34px 22px;border-radius:34px;
  background:linear-gradient(145deg, rgba(23,31,63,.92), rgba(12,18,39,.82));
  border:1px solid var(--line);box-shadow:var(--shadow);text-align:center;overflow:hidden;
}
.hero-card:before{
  content:"";position:absolute;inset:-2px;
  background:radial-gradient(circle at 30% 0%, rgba(255,230,109,.16), transparent 22rem),
             radial-gradient(circle at 85% 30%, rgba(18,214,197,.17), transparent 18rem);
  pointer-events:none;
}
.hero-card>*{position:relative}
.badge,.eyebrow{
  display:inline-flex;align-items:center;gap:8px;
  padding:8px 12px;border-radius:999px;background:rgba(255,230,109,.12);
  color:#fff0a7;border:1px solid rgba(255,230,109,.25);font-weight:800;font-size:.78rem;text-transform:uppercase;letter-spacing:.06em;
}
h1{font-size:clamp(2.05rem, 9vw, 4.8rem);line-height:.95;margin:18px auto;max-width:820px;letter-spacing:-.07em}
.subtitle{max-width:650px;margin:0 auto;color:var(--muted);font-size:1.05rem;line-height:1.6}
.identity-grid{
  display:grid;grid-template-columns:1fr 1fr;gap:12px;max-width:520px;margin:24px auto 0;
}
.identity-grid div{
  padding:16px;border:1px solid var(--line);border-radius:20px;background:rgba(255,255,255,.055);
}
.identity-grid span{display:block;color:var(--muted);font-size:.8rem;margin-bottom:4px}
.identity-grid strong{font-size:1rem}
.hero-actions{display:flex;gap:12px;justify-content:center;flex-wrap:wrap;margin-top:26px}
.primary-btn,.secondary-btn,.tiny-btn{
  border:0;border-radius:999px;cursor:pointer;font-weight:900;transition:.2s transform,.2s filter,.2s background;
}
.primary-btn{
  display:inline-flex;justify-content:center;align-items:center;padding:15px 22px;
  background:linear-gradient(135deg, var(--brand), #9b6dff);color:#fff;box-shadow:0 16px 36px rgba(111,114,255,.32);
}
.primary-btn:hover,.secondary-btn:hover,.tiny-btn:hover{transform:translateY(-2px);filter:brightness(1.06)}
.secondary-btn{
  display:inline-flex;align-items:center;justify-content:center;padding:15px 20px;
  border:1px solid var(--line);background:rgba(255,255,255,.08);color:var(--text);
}
.wide{width:100%;max-width:460px}
.section{max-width:1040px;margin:0 auto;padding:34px 16px}
.section-heading{margin-bottom:20px}
.section-heading h2{font-size:clamp(1.75rem, 6vw, 3rem);line-height:1.02;margin:12px 0 10px;letter-spacing:-.05em}
.section-heading p:not(.eyebrow){color:var(--muted);line-height:1.6;margin:0;max-width:780px}
.accordion-list{display:grid;gap:14px}
.accordion{
  border:1px solid var(--line);background:rgba(17,25,51,.72);border-radius:22px;overflow:hidden;box-shadow:0 14px 34px rgba(0,0,0,.16);
}
.accordion button{
  width:100%;display:flex;justify-content:space-between;align-items:center;gap:12px;
  padding:18px 18px;background:transparent;color:var(--text);border:0;text-align:left;cursor:pointer;
}
.accordion-title{display:flex;flex-direction:column;gap:4px}
.accordion-title strong{font-size:1.05rem}
.accordion-title span{color:var(--muted);font-size:.86rem}
.accordion-icon{width:36px;height:36px;border-radius:50%;display:grid;place-items:center;background:rgba(255,255,255,.08);flex:0 0 auto}
.accordion-content{display:none;padding:0 18px 18px;color:#e4e8ff;line-height:1.6}
.accordion.open .accordion-content{display:block}
.accordion-content ul{padding-left:20px;margin:10px 0}
.accordion-content li{margin:8px 0}
.callout{
  margin-top:12px;padding:12px 14px;border-radius:16px;background:rgba(18,214,197,.1);
  border:1px solid rgba(18,214,197,.22);color:#dffdfa;font-weight:700;
}
.flashcard-toolbar{display:flex;gap:10px;flex-wrap:wrap;margin-bottom:16px}
.tiny-btn{padding:11px 14px;background:rgba(18,214,197,.18);color:#dffdfa;border:1px solid rgba(18,214,197,.28)}
.tiny-btn.ghost{background:rgba(255,255,255,.06);color:var(--text);border-color:var(--line)}
.flashcard-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:14px}
.flashcard{min-height:178px;perspective:1000px;cursor:pointer}
.flashcard-inner{position:relative;width:100%;height:100%;min-height:178px;transition:transform .55s;transform-style:preserve-3d}
.flashcard.flipped .flashcard-inner{transform:rotateY(180deg)}
.face{
  position:absolute;inset:0;padding:18px;border-radius:22px;border:1px solid var(--line);
  background:linear-gradient(145deg, rgba(24,33,67,.95), rgba(12,18,39,.9));
  backface-visibility:hidden;display:flex;flex-direction:column;justify-content:space-between;box-shadow:0 16px 35px rgba(0,0,0,.18)
}
.face.back{transform:rotateY(180deg);background:linear-gradient(145deg, rgba(23,58,67,.95), rgba(12,18,39,.92))}
.face .tag{color:#fff0a7;font-size:.78rem;font-weight:900;text-transform:uppercase;letter-spacing:.05em}
.face strong{font-size:1.22rem;line-height:1.2}
.face p{margin:0;color:#e4e8ff;line-height:1.45}
.quiz-panel,.quiz-form,.results{
  border:1px solid var(--line);border-radius:28px;background:rgba(17,25,51,.78);padding:18px;box-shadow:var(--shadow)
}
.quiz-stat-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:12px;margin-bottom:18px}
.quiz-stat-grid div{padding:18px;border-radius:20px;background:rgba(255,255,255,.055);text-align:center;border:1px solid var(--line)}
.quiz-stat-grid strong{display:block;font-size:2rem}
.quiz-stat-grid span{color:var(--muted);font-size:.84rem;font-weight:800}
.hidden{display:none!important}
.quiz-progress-wrap{position:sticky;top:0;z-index:5;padding:12px;background:rgba(11,16,32,.88);backdrop-filter:blur(16px);border:1px solid var(--line);border-radius:20px;margin-bottom:14px}
.quiz-progress-info{font-weight:900;margin-bottom:8px;color:#e9ecff}
.progress-track{height:10px;border-radius:999px;background:rgba(255,255,255,.09);overflow:hidden}
.progress-bar{height:100%;width:0;background:linear-gradient(90deg, var(--brand-2), var(--brand));border-radius:999px;transition:.2s width}
.question-card{padding:18px;border:1px solid var(--line);border-radius:22px;background:rgba(255,255,255,.045);margin-bottom:14px}
.question-meta{display:flex;justify-content:space-between;gap:10px;color:var(--muted);font-weight:800;font-size:.83rem;margin-bottom:10px}
.question-card h3{font-size:1.04rem;line-height:1.45;margin:0 0 14px}
.option{display:flex;gap:10px;align-items:flex-start;padding:13px;border:1px solid var(--line);border-radius:16px;margin:10px 0;background:rgba(255,255,255,.045);cursor:pointer}
.option input{margin-top:4px;accent-color:var(--brand)}
.option:hover{background:rgba(255,255,255,.08)}
.option-letter{font-weight:950;color:#fff0a7;min-width:22px}
.results-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:12px;margin-bottom:16px}
.result-box{padding:18px;border-radius:20px;background:rgba(255,255,255,.055);border:1px solid var(--line)}
.result-box strong{display:block;font-size:2rem}
.result-box span{color:var(--muted);font-weight:800}
.topic-result{margin:10px 0;padding:12px;border-radius:16px;background:rgba(255,255,255,.05);border:1px solid var(--line)}
.topic-result-header{display:flex;justify-content:space-between;gap:12px;font-weight:900;margin-bottom:8px}
.review-list{display:grid;gap:10px;margin-top:14px}
.review-item{padding:14px;border-radius:16px;background:rgba(255,107,138,.1);border:1px solid rgba(255,107,138,.18)}
.review-item.ok{background:rgba(66,230,164,.1);border-color:rgba(66,230,164,.18)}
.answer-feedback{margin-top:10px;padding:12px;border-radius:14px;background:rgba(0,0,0,.18);color:#e9ecff}
.correct{border-color:rgba(66,230,164,.65)!important;background:rgba(66,230,164,.11)!important}
.wrong{border-color:rgba(255,107,138,.65)!important;background:rgba(255,107,138,.11)!important}
.footer{max-width:1040px;margin:20px auto 0;padding:30px 16px 50px;color:var(--muted);display:flex;justify-content:space-between;gap:18px;flex-wrap:wrap}
.footer a{font-weight:900;color:#fff}
.install-btn{
  position:fixed;left:16px;right:16px;bottom:16px;z-index:20;padding:14px 18px;border-radius:999px;border:1px solid rgba(255,255,255,.2);
  background:linear-gradient(135deg,var(--brand),#9b6dff);color:#fff;font-weight:950;box-shadow:0 18px 50px rgba(0,0,0,.38);
}
@media (max-width:820px){
  .flashcard-grid{grid-template-columns:1fr 1fr}
  .results-grid{grid-template-columns:1fr}
}
@media (max-width:620px){
  .hero{padding-left:10px;padding-right:10px}
  .hero-card{padding:28px 16px;border-radius:28px}
  .topbar{justify-content:space-between}
  .nav-pill{font-size:.82rem;padding:9px 10px}
  .identity-grid,.quiz-stat-grid{grid-template-columns:1fr}
  .hero-actions{flex-direction:column}
  .primary-btn,.secondary-btn{width:100%}
  .flashcard-grid{grid-template-columns:1fr}
  .section{padding:28px 12px}
  .question-card{padding:14px}
}
@media (display-mode: standalone){
  .install-btn{display:none!important}
}