.app-shell {
  display: grid;
  grid-template-columns: 300px minmax(0, 1fr);
  min-height: 100vh;
}

.app-main {
  padding: 28px;
}

.os-sidebar {
  position: sticky;
  top: 0;
  min-height: 100vh;
  padding: 24px 18px;
  border-right: 1px solid rgba(255,255,255,.08);
  background:
    linear-gradient(180deg, rgba(255,255,255,.05), rgba(255,255,255,.02)),
    radial-gradient(circle at top left, rgba(159,124,255,.15), transparent 30%);
}

.brand-block {
  display: grid;
  gap: 8px;
  margin-bottom: 22px;
}

.brand-block h1 {
  margin: 0;
  font-size: 2rem;
}

.brand-block p {
  margin: 0;
  color: var(--muted);
  line-height: 1.5;
}

.brand-kicker,
.eyebrow {
  text-transform: uppercase;
  letter-spacing: .08em;
  font-size: .72rem;
  color: var(--muted);
}

.nav-list {
  display: grid;
  gap: 10px;
}

.nav-link {
  padding: 12px 14px;
  border-radius: 14px;
  border: 1px solid rgba(255,255,255,.08);
  background: rgba(255,255,255,.04);
  transition: .18s ease;
}

.nav-link:hover {
  transform: translateY(-1px);
  border-color: rgba(159,124,255,.24);
  background: rgba(255,255,255,.06);
}

.nav-link.active {
  background: linear-gradient(135deg, rgba(159,124,255,.24), rgba(124,92,255,.28));
  border-color: rgba(159,124,255,.35);
  box-shadow: inset 0 0 0 1px rgba(255,255,255,.04);
}

@media (max-width: 980px) {
  .app-shell {
    grid-template-columns: 1fr;
  }

  .os-sidebar {
    position: static;
    min-height: auto;
    border-right: 0;
    border-bottom: 1px solid rgba(255,255,255,.08);
  }

  .app-main {
    padding: 18px;
  }
}