"There are two key differences between you and these guys; they can't move, and you can't fire deadly ninja-seeking rockets."
— (As written in the N in-game help).
This devious turret will fire a single homing missile at you whenever you are in its line of sight, which is basically everywhere around it that isn't covered by terrain. Only one rocket will be fired by each turret at any one time. If the rocket explodes without killing you, the turret will fire another if you are still within sight. The rocket travels rather quickly, comparable to the ninja's top speed, and has advanced homing software. The turret has a slight delay after it senses you before it fires.
Multiple rockets are hell, as seen in 19-4: quad damage. Difficult terrain, lots of bounceblocks, or enclosed space also allows the rocket to do maximum damage. An extreme and unique example of this is shown in Brickman's 80-3: Full Circle, where you have to keep the rocket behind you all the way.
- 80-3: Full Circle by Brickman
To avoid rockets, you need to learn how it moves. It's difficult to explain in words, since you need experience. Generally, if a rocket is coming straight at you, stand still near some sort of wall or obstacle, and move aside just before it hits. Hopefully it'll loop into the wall and explode, without harming you.
There is one known trick for rockets. It is used in 80-3 by top highscorers. If you confuse the rocket and make it move a certain way, it can loop through the tiling in the center, allowing you to move quickly through the circle without worrying about the rocket being on your tail. This technique is also used to make KRA DDAs, a DDA that keeps the rocket alive throughout the entire course of the map.