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