After moving all objects to prefab folder, when I press the play, I can not see anything except background?
Did you reset the position of your prefabs ?
On double click on your gameobject in hierarchy unity makes a focus on it so you can see where it is.
Maybe it’s just a position problem (it happend for me :D)
thanks for advice but unfortunately that is not a problem. There is something else, everything is on the right position, I have checked all gameObjects in my hierarchy. I notice that till I made the level_02,then I deleted level-2, but now either Level_01 doesn’t show anything except the background.:)So, I started making everything from beginning:(
Just a thought, but check the Transform.position z-value of your objects, and make sure the z-value of your background is higher. A lower number would place your background in front of your objects, and make them invisible.