Unity provides all the low level engine stuff. Both the missile and the falling bomb are GameObjects in Unity jargon. They have positions as Vector3 types. I get them both and get the difference vector. Then according to the magnitude of that, I add acceleration to the rocket and so on...

The trail of the rockets and the smoke they produce are particle creators provided by Unity. You provide the sprites and tweak settings.

It is possible to find add-ons for unity in it's built in asset store to do most of the things but I haven't used it. Except for Google AdMob integration.