body { margin-left: 280px; margin-right: auto; }
#TOC {
  position: fixed;
  top: 2rem;
  left: 1rem;
  width: 220px;
  max-height: 90vh;
  overflow-y: auto;
  font-size: 0.85rem;
  padding-right: 0.75rem;
  border-right: 1px solid #ddd;
}
#TOC ul { list-style: none; margin: 0; padding-left: 0.9rem; }
#TOC > ul { padding-left: 0; }

#toc-toggle {
  position: fixed;
  top: 2rem;
  z-index: 10;
  width: 1.75rem;
  height: 1.75rem;
  border: 1px solid #ccc;
  background: #fff;
  border-radius: 4px;
  cursor: pointer;
  font-size: 1rem;
  line-height: 1.6;
  padding: 0;
}
body:not(.toc-hidden) #toc-toggle { left: 250px; }
body.toc-hidden #toc-toggle { left: 1rem; }

body.toc-hidden #TOC { display: none; }
body.toc-hidden {
  margin-left: auto;
  margin-right: auto;
  max-width: none;
  padding-left: 3rem;
  padding-right: 3rem;
}

@media (max-width: 1000px) {
  #TOC, #toc-toggle { display: none; }
  body { margin-left: auto; }
}