Set MainCamera to adjust 2D game

Unity is also a good tool to develop 2D games, however it is not convenient to design the game on an initial camera shape which is shown bellow:

So, firstly, let's change the shape of MainCamera:

  Change the value of "Projection" from "Perspective" to "Orthographic" shown as bellow:

Then we add directional light and a background of the scene:

• Since the value of z axis controls the layer of the game, so the items of the game must have the same z value! 
• The item with smaller value of z axis is put in front of the bigger value one.