Play it like a normal Roof level, using lobbed-shot plants. Switch in Cabbage-pults for Melon-pults and upgrade Melon-pults to Winter Melons when there is enough sun available. It is necessary to use Sunflowers and Flower Pots, and as the game progresses further, try to get Twin Sunflowers. It is good to have Tall-nuts to protect your plants, and Pumpkins to protect from ambush zombies. Bungee Zombies and Catapult Zombies may appear, so use Umbrella Leaves, but since they only appear in huge waves, you may use Jalapeno against Bungee Zombies or Ice-shrooms to freeze them and other instant kills against catapults. If you have Imitater, use it to quickly place more Tall-nuts and Pumpkins.
