body {
  margin: 0;
  font-family: Arial;
}

.sidebar {
  position: fixed;
  top: 0;
  left: 0;
  width: 260px;
  height: 100vh;

  background: #f7f7f8;   /* softer like ChatGPT light mode */
  color: #111;

  transform: translateX(-105%);
  transition: transform 0.45s cubic-bezier(0.4, 0, 0.2, 1);

  padding: 12px;
  box-shadow: 4px 0 20px rgba(0,0,0,0.08);

  z-index: 1000;
}

.sidebar.active {
  transform: translateX(0);
}

.main {
  transition: transform 0.4s ease, opacity 0.3s ease;
}

.main.shift {
  transform: translateX(10px);
}

.overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.25); /* lighter overlay */
  opacity: 0;
  visibility: hidden;
  transition: 0.3s ease;
}

.overlay.active {
  opacity: 1;
  visibility: visible;
}

.icon-btn {
  font-size: 22px;
  background: none;
  border: none;
  cursor: pointer;

  padding: 6px 10px;
  border-radius: 8px;

  transition: background 0.2s ease;
}

.icon-btn:hover {
  background: rgba(0,0,0,0.05);
}