You're in charge to destroy many buildings ! Pick the best moment to go down with your crane for your wrecking ball to destroy as much part of the building as possible.
But be careful, not every parts of the building can be destroyed, only the ones with windows. Collide with the wrong part of the building and your wrecking ball will be destroyed, meaning your failure.
If you achieve to hit the TNT block, you enter in fever mode and can destroy everything you want !