Resistance force generator for use in a game machine

An operation device that communicates with a game device that generates game information and communicates said game information to a resistance force generator incorporated in said operation device, said operation device comprising:

• input means that communicates input device information to said game device, said resistance force generator further comprising:
• a container which accommodates a particulate magnetic substance that is movable from an inactive position to an activated position;
• a rotation member provided inside said container and connected to said input means, said rotation member being rotatable in response to operation of said input means and independent of said game information;
• and
• a magnetic field generation means which generates a magnetic field inside said container in accordance with game information generated by said game device and which causes said particulate magnetic substance to move from said inactive position to said activated position upon activation of a magnetic field inside said container,
• wherein said particulate magnetic substance in said inactive position generates a first resistance to rotation in said rotation member, and
• wherein said particulate magnetic substance in said activated position generates a second resistance to rotation in said rotation member,
• said first and second resistances to rotation generating first and second resistances to movement in said input means in accordance with game information.