How to implement a Worms style destructible terrain in XNA?

Riemer has a similar approach to a game he developed in XNA, cannon shells cause the terrain to be "destroyed" and any props that were previously on said terrain are moved accordingly.

It needs to be refactored and improved for your needs but it's a start.

Riemer has a good selection of tutorials for other things too.

http://www.riemers.net/eng/Tutorials/XNA/Csharp/Series2D/Adding_craters.php

There are two possibilties, eighter one work, but it depends on XNA how easy it is to implement:

• Like others suggested, bitmap masking. You keep a bitmap of all "ground" pixels and all "air" pixels. If you have gravity; a character can't fall through ground, while it can fall through air.
• Vector geometry. You start with a rectangular "ground", and hold a list of "removed" ground, which creates air. This geometry is very simple to edit: just append a circle or similar to the list, and update the graphics. I don't know whether XNA has vector & shape abilities; but it should be easy to create geometry with these two things, and later apply a texture or similar. Also, this can be easy to optimize, by keeping a cached version of the rendered landscape, and only update the cache of the bounding-box of the newly added "air". This solution requires a bit more math though.