Sentries

Sentries are undefeatable, immovable objects that sometimes spawn exclusively in Mechtropolis. They can appear in two colors, which determine the rotation. They usually spawn in the middle of the room, but can be found on top of cars as well.

They usually spawn with other gunner type droids, making it annoying to fight droids while they exist.

Information
Sentries attack by spinning 360 degrees, while shooting bullets at the rate of a Rapid-Fire Droid. However, their bullets do more damage, doing a whopping 10  per bullet. These bullets can be dodged by jumping, getting behind shelter, or jumping onto the sentry itself. After completing the stage, the sentry will shut off, and will never be active again.

Trivia

 * Red sentries rotate clockwise, and blue sentries rotate counterclockwise.
 * They can spawn on top of cars, the middle of the room, or other places.
 * These can be stopped by putting a cauldron on them if they are in the middle of the room with the Alchemist ability.