Every few waves it turns night for one wave causing turrets to be unable to attack enemies in the dark.
Levels 5,11,36 are nights
Here are a variety of ways to defend against the night.
1: Use the delete button to dig 2 blocks under the ground. Build a power generator there. Cover the block above it with any block, preferably wood. Now dig holes for lights around the area of the generator. This makes perfect bait blocks and night vision as well! ~Hexapheonix.
2: Over time, work on crafting detector mods for your favorite turrets. This mod allows them to see in the dark.
(Post your defenses against the night here if you wish to share)