Move the angle slider a (blue) to make rotated copies of polygon BCDEF.[br]Click the checkbox, then move the angle slider b (red) to rotate the entire pattern.[br]Move points B, C, D, E, F to change the shape of the polygon.[br]Move point A to change the center of rotation.[br][br]If the rotated (red) pattern lines up with the original (blue) pattern, then the pattern has rotational symmetry, by the angle b.