As mentioned with the previous game in Chapter 4, Advanced Game Content Generation with a Fruit Chopper Game instead of explaining the mechanism of the gameplay loop it will be better for you to work from scratch or to understand the current logic you got with the book. With that said, let's break down the gameplay logic:
Once the game starts and as long as the score is less than 100; the levelLayout blueprint will keep moving the Blocks transform towards the left to give the appearance of a running level. Once the Blocks transform reaches its endpoint (completes showing the last block) the levelLayout blueprint will reset the position of the Blocks transform and show the collectables, to start displaying the level continually again.
The madScientist blueprint, which is the player, will start receiving the inputs from the touchscreen or the keyboard/mouse. As long as the player is running on the ground, the animated sprite will display a running loop animation; otherwise...