public void StartNewGame(Grid grid, Difficulty difficulty = Difficulty.Unknown)
{
ValidatorGrid.EnsureGridIsValid(grid);
_grid = grid.Clone();
_solutionGrid = _solver.SolveGivens(_grid);
Difficulty = difficulty;
GridChanged();
_historyManager.ClearRedo();
_historyManager.ClearUndo();
SetModalState(ModalState.None);
_colorManager.Clear();
_gameTimerManager.StartTimer();
}