Making a mask

How do I make a mask like this?

<img src="http://i.imgur.com/HYSHjlp.png" border="0" />

I want the circle to move with the character and see through the black background.

I have tried so many times but I failed so hard.Could someone help please?

Well, I can think of 2 ways:

1. Open C2 and check "Lighting" example

2. Create a very big black sprite with a hole in it. And then pin the sprite to player

Thanks bro!I prefer the first one! <img src="smileys/smiley1.gif" border="0" align="middle" />