I have myMask (a circular shape initially) which will be controlled using left-Right-Up-Down keys.
I have an image myBackgroud image which remains still.

What i want to do is that when myMask passes on myBackground, the image that we see on screen is ONLY what is within myMask.
Just imagine a magnifying glass that u passes on a picture

What u see in it is Another picture. The magnifying glass is then a mask...