#editor {
  border: 1px solid #ccc;
  border-radius: 6px;
  padding: 8px;
  width: 100%; /* fill entire row */
  max-width: none; /* remove the 600px cap */
  box-sizing: border-box; /* include padding/border in width */
}

.toolbar {
  border-bottom: 1px solid #ddd;
  margin-bottom: 6px;
  padding-bottom: 4px;
}

.toolbar button {
  border: none;
  background: #f6f8fa;
  padding: 5px 8px;
  margin-right: 4px;
  cursor: pointer;
  border-radius: 4px;
}

.toolbar button:hover {
  background: #e1e4e8;
}

textarea {
  width: 100%;
  min-height: 200px; /* make it taller if needed */
  margin-bottom: 10px;
  font-family: monospace;
  box-sizing: border-box;
}

.preview {
  border-top: 1px solid #ddd;
  padding-top: 6px;
}