P5: PP | PP | PP | PP | PP (7 | 7 | 7 | 7 | 7)
We're on the roof, so let's take a look at the easiest strategy on this stage.
There are no discos and diggers on the roof so the 10 cob setup works well.
On roof, imp can land on column 5 so cobs are moved 1 column to the front.
Stall gigas when they get too close to the front line.
Use ice to kill ambush zombies on wave 20.