Text this: Dynamics of a Rotating Sphere on Free Surface of Vibrated Granular Materials

  ______    ______   ______     ______   _    _   
 /_   _//  /_   _// |      \\  /_   _// | || | || 
   | ||     -| ||-  |  --  //   -| ||-  | || | || 
  _| ||     _| ||_  |  --  \\   _| ||_  | \\_/ || 
 /__//     /_____// |______//  /_____//  \____//  
 `--`      `-----`  `------`   `-----`    `---`