The key to this game is using the landslides. When you use the
jackhammer to connect the cracks remember this:
The answer is simple: which ever portion is smaller will be destroyed,
so stay on the larger portion.
For the earlier level, just herd all the enemies to to one side, and go
up and down the cracks, and then destroy them. Repeat for each
of the levels.
Once you get past level 16, you get the achievement: