.lesson {
  display: grid;
  grid-template-columns: 220px 1fr;
  gap: 1.5rem;
  align-items: start;
  padding-bottom: 4rem;
}
.lesson__nav {
  position: sticky;
  top: 84px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1rem;
  box-shadow: var(--shadow);
}
.lesson__nav h2 {
  margin: 0 0 .75rem;
  font-size: .78rem;
  text-transform: uppercase;
  letter-spacing: .08em;
  color: var(--muted);
}
.lesson__nav a {
  display: block;
  padding: .42rem .55rem;
  border-radius: 10px;
  color: var(--ink);
  font-size: .9rem;
}
.lesson__nav a:hover { background: var(--accent-soft); color: var(--accent-ink); }

.lesson__content {
  display: grid;
  gap: 1rem;
  min-width: 0;
}
.lesson__block {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.35rem 1.4rem;
  box-shadow: var(--shadow);
  scroll-margin-top: 90px;
}
.lesson__block h2 {
  margin: 0 0 .75rem;
  font-size: 1.4rem;
  letter-spacing: -.02em;
}
.lesson__block h3 {
  margin: 1.2rem 0 .45rem;
  font-size: 1.05rem;
}
.lesson__block p,
.lesson__block li {
  color: #334155;
  font-size: 1rem;
  line-height: 1.65;
}
.lesson__block p { margin: 0 0 .85rem; }
.lesson__block ul,
.lesson__block ol {
  margin: 0 0 1rem;
  padding-left: 1.2rem;
}
.lesson__block li { margin-bottom: .35rem; }

.lesson__analogy {
  margin: 0 0 1rem;
  padding: .9rem 1rem;
  border-radius: 14px;
  background: var(--accent-soft);
  border: 1px solid #a7f3d0;
  color: var(--accent-ink);
  font-size: .95rem;
}
.lesson__analogy strong { color: #065f46; }

.lesson__callout {
  margin: 0 0 1rem;
  padding: .9rem 1rem;
  border-radius: 14px;
  background: #fff7ed;
  border: 1px solid #fed7aa;
  color: #9a3412;
  font-size: .95rem;
}

.lesson__demo {
  margin: 1rem 0;
  border: 1px solid var(--line);
  border-radius: 14px;
  overflow: hidden;
  background: #0f172a;
  color: #e2e8f0;
  font-family: var(--mono);
  font-size: .84rem;
}
.lesson__demo-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: .75rem;
  padding: .65rem .9rem;
  background: #1e293b;
  color: #94a3b8;
  font-size: .78rem;
}
.lesson__demo-body { padding: .9rem; line-height: 1.55; }
.lesson__demo .ok { color: #6ee7b7; }
.lesson__demo .warn { color: #fbbf24; }
.lesson__demo .err { color: #fca5a5; }
.lesson__demo .muted { color: #94a3b8; }

.codes {
  display: grid;
  gap: .65rem;
}
.code-row {
  display: grid;
  grid-template-columns: 72px 1fr;
  gap: .85rem;
  align-items: start;
  padding: .8rem .9rem;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: #f8fafc;
}
.code-row__n {
  font-family: var(--mono);
  font-weight: 700;
  font-size: 1.05rem;
}
.code-row__n.is-2xx { color: #047857; }
.code-row__n.is-3xx { color: #0369a1; }
.code-row__n.is-4xx { color: #c2410c; }
.code-row__n.is-5xx { color: #b91c1c; }
.code-row h3 {
  margin: 0 0 .2rem;
  font-size: .98rem;
}
.code-row p {
  margin: 0;
  font-size: .92rem;
  color: var(--muted);
}

.steps {
  display: grid;
  gap: .7rem;
  margin: 0;
  padding: 0;
  list-style: none;
  counter-reset: step;
}
.steps li {
  position: relative;
  padding: .85rem 1rem .85rem 3rem;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: #fff;
  color: #334155;
}
.steps li::before {
  counter-increment: step;
  content: counter(step);
  position: absolute;
  left: .85rem;
  top: .9rem;
  width: 1.5rem;
  height: 1.5rem;
  border-radius: 999px;
  background: var(--accent-soft);
  color: var(--accent-ink);
  font-weight: 700;
  font-size: .85rem;
  display: grid;
  place-items: center;
}

.lesson__next {
  display: flex;
  flex-wrap: wrap;
  gap: .75rem 1rem;
  margin-top: .5rem;
  font-size: .92rem;
}

.mini-table-wrap {
  overflow-x: auto;
  margin: .85rem 0 1rem;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: #fff;
}
.mini-table {
  width: 100%;
  border-collapse: collapse;
  font-size: .9rem;
  min-width: 320px;
}
.mini-table th,
.mini-table td {
  padding: .55rem .75rem;
  border-bottom: 1px solid var(--line);
  text-align: left;
}
.mini-table th {
  background: #f8fafc;
  color: var(--muted);
  font-weight: 600;
  font-size: .78rem;
  text-transform: uppercase;
  letter-spacing: .04em;
}
.mini-table tr:last-child td { border-bottom: 0; }
.mini-table .hl {
  background: #ecfdf5;
  font-weight: 600;
}
.mini-table caption {
  caption-side: top;
  text-align: left;
  padding: .65rem .75rem .2rem;
  font-size: .82rem;
  color: var(--muted);
  font-weight: 600;
}

@media (max-width: 900px) {
  .lesson { grid-template-columns: 1fr; }
  .lesson__nav { position: static; display: flex; flex-wrap: wrap; gap: .25rem; }
  .lesson__nav h2 { width: 100%; }
  .code-row { grid-template-columns: 1fr; gap: .35rem; }
}