What happens with platform on second level when the first level is destroyed? Does all the construction crumble and fall apart? Or does it just fall down one level and previously second level is now first?
page 9 ; you can find :
If there are no Heroes in the Enemy’s line of sight, the ranged attack instead targets and destroys the highest pillar of the closest platform in the Enemy’s line of sight and range. If there is no legal ranged attack target in the Enemy’s line of sight, the attack is skipped.
So the first level can not be destroyed before the second level.
always the highest pillar
.. and yes, this rulesbook is apocalyptic !