Simplify the following text for a Grade 7 native English-speaking person.
Original: Riordan created the fictional character Percy Jackson and made the story of how he would travel across the United States to recover Zeus 's lightning bolt .
Simplified: When Haley wanted him to make up stories of his own using the characters from the myths , Riordan created the character of Percy Jackson . He made up the story of how Percy traveled across the United States to search for Zeus ' master bolt .