src/styles/dark-mode.css

.dark-mode {
  background: #1c1c1c;
  color: white;
}

.dark-mode .excel-toolbar {
  background: linear-gradient(to right, #444, #222);
}

.dark-mode .excel-toolbar button {
  color: #222;
}

.dark-mode .excel-grid {
  filter: brightness(0.9);
}