The following section describes how to define a Bob (blitter object). Like
VSprites, a Bob is a software construct designed to make animation easier.
The main advantage of a Bob over a VSprite is that it allows more colors
and a width greater than 16 pixels to be defined.

To create a Bob, you need both a bob structure and a vsprite structure.
The components common to all GELs -- height, collision-handling
information, position in the drawing area and pointers to the image
definition -- are part of the VSprite structure.  The added features --
such as drawing sequence, data about saving and restoring the background,
and other features not applicable to VSprites -- are further specified in
the Bob structure.

 the vsprite structure and bobs        bob priorities 
 vsprite flags and bobs                adding a bob 
 the bob structure                     removing a bob 
 using bob flags                       sorting and displaying bobs 
 specifying the size of a bob          changing bobs 
 specifying the shape of a bob         complete bob example 
 specifying the colors of a bob        double-buffering 
 other items influencing bob colors