In this recipe, you added the empty GameObjects called corner_max and corner_min to the scene. The X and Y coordinates of these GameObjects will be used to determine the bounds of movement that we will permit for the player-controlled character; that is, player-spaceGirl. Since these are empty GameObjects, they will not be seen by the player when in play-mode. However, we can see and move them in the Scene window and since we added the yellow oblong icons, we can see their positions and names very easily.
When the Awake() method is executed for the PlayerMoveWithLimits object inside the player-spaceGirl GameObject, the maximum and minimum X and Y values of the corner_max and corner_min GameObjects are recorded. Each time the physics system is called via the FixedUpdate() method, the velocity of the player-spaceGirl character is updated to the value set in the Update() method, which is based on the horizontal and vertical keyboard/joystick inputs...