2D UFO Tutorial
Create a simple 2D UFO game that teaches you many of the principles of working with Unity and creating 2D games.
In your first foray into Unity development, create a simple 2D UFO game that teaches you many of the principles of working with Game Objects, Components, Prefabs, Physics and Scripting.
Source: https://unity3d.com/learn/tutorials/projects/2d-ufo-tutorial