In the sample project for this chapter, you'll find a Tower prefab in the Prefabs folder. The tower itself is quite simple; it's just a group of primitives arranged to look like a cannon, as you can see in the following screenshot:
The barrel of the gun is affixed to the spherical part of the tower. The gun can rotate freely on its axis when tracking the player so that it can fire in the direction of its target, but it is immobile in every other way. Once the tank gets far enough away, the tower cannot chase it or reposition itself.
In the sample scene, there are several towers placed throughout the level. As they are prefabbed, it's very easy to duplicate towers, move them around, and reuse them between the levels. Their setup is not terribly complicated either. Their hierarchy looks similar to the following...
