The narrator tells us that he's going to go on a school trip to an amusement park. He's happy because he'll be able to play with his big brother, who's also going to be going on the trip. The two of them decide to go to the ocean ball park instead of going to the other amusement park, because the ocean balls can be used for making "particle model bosons" and "fermions" . They decide to play in the "ball pit" instead of the other park because it's safer, and because they're both in the same study group. The narrator is all, "hey, why don't you play with me instead of daodao?" . He wants to join in on the fun, too, but he doesn't want to be seen as a pretentious brat.