private void NewLevelSet()
{
if (!ConfirmClose())
{
return;
}
CloseLevelSet();
var level = CreateNewLevel(0);
_levelSet.Add(level);
UpdateTitle();
rightTabControl.TabPages.Add(new LevelEditorTabPage(this, level));
UpdateRightTabControlVisible();
UpdateLevelMenuItemsEnabled();
IsChanged = false;
}