Accessory and control method

An accessory suitable for disposing on an electronic device, which has a plurality of first device elements disposed adjacent to first and second edges of the electronic device, the accessory comprising:

• a cover has a plurality of first cover elements disposed in the cover, at least one of the first cover elements attracted to at least one of the first device elements along each edge of the electronic device;
• wherein when one of the first cover elements is not attached to the one of the first device elements along the first edge of the electronic device, the cover is flipped along the second edge of the electronic device and the first cover elements along the second edge are attracted to the first device element along the corresponding edge of the cover, and when one of the first cover elements is not attached to the one of the first device elements along the second edge of the electronic device, the cover is flipped along the first edge of the electronic device and the first cover elements along the first edge are attracted to the first device element along the corresponding edge of the cover,
• wherein when the first cover element and the corresponding first device element are two magnets attracted to each other, a north pole and a south pole of the first cover element are arranged in a first axis which is parallel to the cover and perpendicular to edges of the cover corresponding to the first and the second edges of the electronic device, a north pole and a south pole of the first device element are arranged in a second axis which is opposite to the first axis, parallel to the cover, and perpendicular to the first and the second edges of the electronic device,
• wherein magnetic polarities of the first cover elements facing the edges of the cover are the same,
• wherein the placement of the first cover elements in the cover forms a symmetrical pattern respect to a third axis which is parallel to the first edge and goes through a geometrical center of the cover and a fourth axis which is parallel to the second edge and goes through the geometrical center of the cover,
• wherein the cover has a front surface and a rear surface opposite to each other and parallel to the first axis, and a distance between the first axis and the front surface is equal to a distance between the first axis and the rear surface,
• wherein when the cover is flipped, an attraction between the first cover element and the corresponding first device element is kept and one of the first and second edges of the electronic device is tightly attached to corresponding edge of the cover, and
• wherein the cover is able to rotate 360 degrees about each of the first and second edges of the electronic device.