Challenge of producing guidelines to address different needs.
Some users:
- Need audio and synthesized speech;
 
- Need images, video, and graphics;
 
- Require time-independent control (e.g., those using serial
access or with physical disabilities);
 
- Require space-independent control (e.g., can't use the mouse to
navigate in two dimensions);
 
- May have more than one disability.
 
Note: Plain text help content is 
not the best solution.