:root{
  --bg:#0b1020;
  --panel:#121a33;
  --panel2:#0f1630;
  --text:#e7ecff;
  --muted:#a6b0dd;
  --accent:#7c5cff;
  --border:rgba(255,255,255,.08);
}
*{box-sizing:border-box}
body{
  margin:0;
  font-family: ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Arial;
  background: radial-gradient(900px 600px at 20% 0%, rgba(124,92,255,.22), transparent 60%), var(--bg);
  color:var(--text);
}
code{color:#d7d0ff}
.header{
  display:flex;
  align-items:center;
  justify-content:space-between;
  padding:18px 20px;
  border-bottom:1px solid var(--border);
  background:rgba(10,14,30,.65);
  backdrop-filter: blur(8px);
  position:sticky;
  top:0;
}
.header h1{margin:0;font-size:18px;letter-spacing:.2px}
.subtitle{margin:4px 0 0 0;color:var(--muted);font-size:13px}
.actions{display:flex;gap:10px;align-items:center}
button{
  background:var(--accent);
  border:none;
  color:white;
  padding:10px 12px;
  border-radius:10px;
  cursor:pointer;
  font-weight:600;
}
button:hover{filter:brightness(1.05)}
.link{
  color:var(--text);
  text-decoration:none;
  border:1px solid var(--border);
  padding:9px 12px;
  border-radius:10px;
  background:rgba(255,255,255,.03);
}
.link:hover{border-color:rgba(124,92,255,.5)}
.layout{
  display:grid;
  grid-template-columns: 360px 1fr;
  gap:14px;
  padding:14px;
}
.sidebar{
  background:rgba(18,26,51,.8);
  border:1px solid var(--border);
  border-radius:14px;
  overflow:hidden;
}
.search{padding:12px;border-bottom:1px solid var(--border);background:rgba(255,255,255,.02)}
.search input{
  width:100%;
  padding:10px 12px;
  border-radius:10px;
  border:1px solid var(--border);
  background:rgba(8,10,20,.55);
  color:var(--text);
}
.levels{padding:10px;max-height: calc(100vh - 170px); overflow:auto}
.level{margin-bottom:12px}
.levelTitle{font-size:13px;color:var(--muted);margin:10px 4px}
.item{
  display:block;
  width:100%;
  text-align:left;
  padding:10px 10px;
  border-radius:12px;
  border:1px solid transparent;
  background:transparent;
  color:var(--text);
  cursor:pointer;
}
.item:hover{background:rgba(255,255,255,.04)}
.item.active{border-color:rgba(124,92,255,.55); background:rgba(124,92,255,.12)}
.item .id{color:var(--muted);font-size:12px;margin-right:8px}
.item .title{font-weight:700}
.item .summary{color:var(--muted);font-size:12px;margin-top:6px;line-height:1.3}

.content{
  background:rgba(18,26,51,.55);
  border:1px solid var(--border);
  border-radius:14px;
  padding:16px;
}
.status{color:var(--muted);font-size:13px;margin-bottom:10px}
.lesson h2{margin:0 0 6px 0;font-size:20px}
.lesson .meta{color:var(--muted);font-size:13px;margin-bottom:16px}
.card{
  background:rgba(255,255,255,.03);
  border:1px solid var(--border);
  border-radius:14px;
  padding:14px;
  margin-bottom:12px;
}
.card h3{margin:0 0 8px 0;font-size:14px;color:#dcd6ff}
.card p{margin:0;line-height:1.45;color:var(--text)}
.test ol{margin:8px 0 0 18px;color:var(--muted)}
.badge{display:inline-block;padding:6px 10px;border-radius:999px;background:rgba(124,92,255,.18);border:1px solid rgba(124,92,255,.35);margin-right:8px}
.footer{padding:12px 16px;color:var(--muted);border-top:1px solid var(--border)}

@media (max-width: 980px){
  .layout{grid-template-columns:1fr}
  .levels{max-height: 360px}
}