Hypocycloid prove that an epicycloid with "k" cusps moves snugly inside one with "k"+1 cusps. The evolute of a hypocycloid is an enlarged version of the hypocycloid itself, while the involute of a hypocycloid is a reduced copy of itself. The pedal of a hypocycloid with pole at the center of the hypocycloid is a rose curve. The isoptic of a hypocycloid is a hypocycloid. Curves similar to hypocyloids can be drawn with the Spirograph toy. Specifically, the Spirograph can draw hypotrochoids and epitrochoids. The Pittsburgh Steelers' logo, which is based on the Steelmark, includes three astroids (hypocycloids of four cusps).
Super City (toy) Super City (toy) The Super City toy is a construction set produced by Ideal Toys in 1967. It is similar to Lego, small plastic pieces which are assembled to create complex structures. However Super City is more oriented to buildings and allows more sophisticated constructions. Children could build skyscrapers, research laboratories and pharmaceutical factories. Super City is made of plastic frames which connect at the edges with grooves and studs into which fit a variety of wall panels. Frames can be connected at right angles by grooved and flanged columns. Frames are primarily square with some rectangles (half squares) and