title: How to create basic "fog of war" effect in Actionscript 3?
body: <p>Hey all.  I'm working on a little flash game, that is a top down game.  Your character is placed in a 600x800 pixel area, and you can use the arrow keys to walk around (in 8 directions).  The object of the game is to avoid getting eaten by the enemy.</p>
  
  <p>To make the game more interesting, I want to create a "fog of war" effect, so you can't see the entire map, but rather, only a small area around your character.  I'm thinking of keeping things very basic, what I'm looking for is the entire map to be blacked out, but a "circle of visibility" around your character.  Like this:</p>
  
  <p><img src="https://i.stack.imgur.com/zcpBH.png" alt="alt text"></p>
  
  <p>Of course, as the player moves around the map, the circle of visibility would move with him.  If there were obstacles, they would come "into view" as the player moved toward them.</p>
  
  <p>I am not sure where to begin on implementing this feature.  I'm using actionscript 3 and would really appreciate your help on giving me ideas on how to implement it!  Thank you!</p>