Destructible Environment

Why making my game, I ran into a little problems trying to make Destructible Environment.

My question is how would you make a 2d image into something that you can slower destroy like
in worm armageddon.

plz help.

I have no experience with 2d games but you should be able to get the pixels in a circle (explosion area) if you have a center coordinate and a radius. Then you would just set these pixels to transparent.