fn makeMove(self: *@This(), move: BitMove, flag: Moves) void {

    fn makeMove(self: *@This(), move: BitMove, flag: Moves) bool {

                // preserve board state
                // const bckup = self.backup(); FIXME

                // preserve board state, so we can rewind illegal moves
                const bckup = self.backup();

                    // make sure the move is valid (no check)
                    const king_square = switch (self.side) {
                        .white => @intToEnum(Square, @ctz(
                            @bitCast(BoardType, self.bitboards[Chess.PE.K.int()]),
                        )),
                        .black => @intToEnum(Square, @ctz(
                            @bitCast(BoardType, self.bitboards[Chess.PE.k.int()]),
                        )),
                    };
                    if (self.isSquareAttacked(king_square, self.enemy)) {
                        self.restore(bckup);
                        return false;
                    }
                    return true;

                    self.makeMove(move, .all);

                    return self.makeMove(move, .all);

                return;

                return false;

            gs.makeMove(move, .all);

            _ = gs.makeMove(move, .all);

            gs.occupancies[0].show();
            gs.occupancies[1].show();