Bombs may be placed on the lower floor beneath the passages in order to conceal them. Very powerful bombs that are concealed in this way may be potentially deadly to both players on the lower and upper floors. Bombs can be thrown and stacked against the wall may be able to blast enemies on the upper passages as well. Bombs may also be thrown up onto the upper floor to hit opponents who are there.
When Sudden Death begins, the left and right walls will start to close in on the stage.
If you are hit by these blocks you lose.
Baku Bomberman Official Guidebook, pg. 102