It’s a really big question. We used the same engine that was created for the action game, but changed many things to develop a strategy game. Actually we are now developing a completely different game though based on the original action. Just like in every strategy we have included many new features: construction of bases, recruiting and hiring of staff, purchasing of various ammunition, research, manufacturing, etc.
You can find more information on Heavy Duty at the Akella site, and read the full E3 interview in our E3 section.