The first boss appears as a large version of the Sweepers, who comes in waves, accompanied by two other Sweeper enemies, and a new enemy, a humanoid vessel floating on a cloud, which can move in any non-black space. They can climb walls, and extinguish fires. When they find Xbox games, they dance around and also play fan-fare.
The second boss appears as a large version of the Sweeper accompanied by two other Sweeper enemies, which can shoot and perform other Sweeper-like attacks, but which don't use fires. This boss has a unique defense pattern.
The third boss appears as a large version of the Sweepers accompanied by two other Sweeper enemies. The Sweepers in 1.5.1 have a new pattern of attacking, which is less effective than the previous Sweepers, but more annoying. Any drone that enters the "Sweeper Zone" becomes invisible, and attacks enemies.
The fourth boss appears as a huge Sweepers accompanied by a bunch of Sweeper enemies. The Sweepers in 1.5.1 have a new special ability, and they no longer start fires, but extinguish fires. It also has a new defense pattern d2c66b5586