You are an experienced programmer and have a problem with the engine, shaders, or advanced effects? Here you'll get answers. No questions about C++ programming or topics which are answered in the tutorials!
Talking about worms all the time... think even the old ms-dos "gorillas" had that "earth eating" in. damn... where's my basic compiler... gotta play again.
For rotation, make the engine render Orthogonal (Look up in the doc how to do this) and use billboards for images. Then you can use the 3D rotation functions to rotate it and I think it will be very fast too.
So basically, if you had a larger map, then you'd split it into smaller chunks and process & render each seperately. 256x256 each for example. Then you also have to calculate when you're 'eating' ground that envolves more than 1 square. But that's simple math I think. Hope it gives you some ideas.