:root{
  --bg:#0b0f17;
  --card:#121a29;
  --text:#e8eefc;
  --muted:#a9b5d3;
  --border:rgba(255,255,255,.12);
  --accent:#6ea8fe;
}

*{ box-sizing:border-box; }

body{
  margin:0;
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Arial;
  background:var(--bg);
  color:var(--text);
}

.header{
  position:sticky;
  top:0;
  z-index:10;
  background:rgba(11,15,23,.9);
  border-bottom:1px solid var(--border);
  backdrop-filter: blur(8px);
}

.header__inner{
  padding:16px 18px;
  max-width:980px;
  margin:0 auto;
}

.title{
  margin:0;
  font-size:18px;
}

.tabs{
  display:flex;
  gap:8px;
  flex-wrap:wrap;
  margin-top:10px;
}

.tab{
  cursor:pointer;
  padding:8px 10px;
  border-radius:12px;
  border:1px solid var(--border);
  background:rgba(255,255,255,.03);
  color:var(--muted);
}

.tab--active{
  background:rgba(110,168,254,.12);
  border-color:rgba(110,168,254,.25);
  color:var(--text);
}

.main{
  max-width:980px;
  margin:0 auto;
  padding:18px;
}

.card{
  background:var(--card);
  border:1px solid var(--border);
  border-radius:16px;
  padding:16px;
  box-shadow: 0 10px 28px rgba(0,0,0,.35);
}

.row{
  display:flex;
  gap:12px;
  flex-wrap:wrap;
  align-items:center;
}

.spacer{ flex:1; }

.btn{
  cursor:pointer;
  padding:9px 12px;
  border-radius:12px;
  border:1px solid var(--border);
  background:rgba(255,255,255,.04);
  color:var(--text);
}

.btn:hover{ background:rgba(255,255,255,.07); }

.muted{ color:var(--muted); }

.pill{
  display:inline-block;
  font-size:12px;
  padding:4px 10px;
  border-radius:999px;
  background:rgba(110,168,254,.14);
  color:var(--accent);
  border:1px solid rgba(110,168,254,.22);
}

.flash{
  min-height:160px;
  display:flex;
  align-items:center;
  justify-content:center;
  text-align:center;
  font-size:20px;
  padding:18px;
  border-radius:16px;
  border:1px dashed rgba(255,255,255,.18);
  background:rgba(255,255,255,.03);
  user-select:none;
}

.grid{
  display:grid;
  grid-template-columns: 1fr;
  gap:10px;
  margin-top:12px;
}

.choice{
  padding:10px 12px;
  border-radius:14px;
  border:1px solid var(--border);
  background:rgba(255,255,255,.03);
  cursor:pointer;
}

.choice:hover{ background:rgba(255,255,255,.06); }

.choice--correct{ border-color: rgba(76,175,80,.65); }
.choice--wrong{ border-color: rgba(244,67,54,.65); }

.input, .select{
  padding:10px 12px;
  border-radius:12px;
  border:1px solid var(--border);
  background:rgba(255,255,255,.03);
  color:var(--text);
  width:min(520px, 100%);
}

.result{
  margin-top:10px;
  padding:10px 12px;
  border-radius:14px;
  border:1px solid var(--border);
  background:rgba(255,255,255,.03);
}