The following manuals are in sequence, you must read them in the given order to have better understanding

1. VGA Retro Game Introduction - DE0-NANO
   

   Read more: VGA Retro Game Introduction - DE0-NANO

2. VGA Retro Sprites and Sound Synthesis - DE0-NANO
   

   Read more: VGA Retro Sprites and Sound Synthesis - DE0-NANO

3. PC Engine / Turbografx-16 - DE0-NANO
   

   Read more: PC Engine / Turbografx-16 - DE0-NANO