.lesson-header {
  background: var(--paper);
  border-bottom: 2px solid var(--ink);
  padding: 0.6rem 0;
  position: sticky; top: 0; z-index: 100;
  box-shadow: 0 2px 0 var(--accent);
}
.lesson-header .container { max-width: none; padding: 0 1rem; }
.lesson-header-inner {
  display: flex; align-items: center; justify-content: space-between;
  flex-wrap: wrap; gap: 0.5rem;
}
.lesson-title {
  font-family: var(--font-display);
  font-size: 1.05rem; font-weight: 700; color: var(--ink);
  display: flex; align-items: baseline; gap: 0.5rem;
  flex-wrap: wrap;
}
.lesson-title .lesson-num { color: var(--accent); font-size: 0.85rem; font-weight: 700; }
.lesson-title .lesson-jp { font-family: var(--font-jp); }
.lesson-title .lesson-en {
  font-size: 0.68rem; color: var(--text-muted);
  font-family: var(--font-sans); font-weight: 500;
}
.lesson-sec-badge {
  display: inline-flex; align-items: center;
  font-family: var(--font-jp); font-size: 0.78rem; font-weight: 700; color: var(--accent);
  background: var(--card-2); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 0.1rem 0.55rem;
}
.back-link { font-size: 0.8rem; color: var(--text-secondary); display: flex; align-items: center; gap: 0.3rem; font-family: var(--font-sans); font-weight: 500; }
.back-link:hover { color: var(--accent); text-decoration: none; }
.section-pills { display: flex; gap: 0.35rem; flex-wrap: wrap; }
.section-pill {
  padding: 0.3rem 0.65rem; border-radius: var(--radius);
  font-size: 0.75rem; font-weight: 700; font-family: var(--font-sans);
  cursor: pointer; border: 1px solid var(--border); background: transparent;
  color: var(--text-secondary); transition: all 0.15s ease; white-space: nowrap;
  display: inline-flex; align-items: center; text-decoration: none;
}
.section-pill:hover { border-color: var(--accent); color: var(--accent); text-decoration: none; }
.section-pill.active { background: var(--accent); color: #fff; border-color: var(--accent); text-decoration: none; }