Look at a very very old video game. The ghosts just won't stop. Never!! Can you imagine having to write thousands of motion blocks one under the other? How boring it would be ... And pointless, they would come to an end sooner or later..
Fortunately for us the control structure is there forever. No matter what blocks we put in the belly of forever, they will be executed in sequence and start again from the beginning.
TODO: Create one, two or more enemies of your hero move forever starting at the moment the game starts (click on the green flag). If an enemy is "sticking" to the boundaries of your Stage, find out how you can change their movement using the blocks turn ή if on edge, bounge.