Why does the author take "changing face" as the topic?

Father is a "face-changing king" Who doesn't love dad, but dad makes me "it's not easy to say I love you". Just look at his figure, he is not tall, but his stomach is round, which is really far from my hero image. I have a father who can change his face. He will put on an angry face, a caring face and a humorous face. First, let's look at his angry expression. My father is fiercer than a tiger when he is angry. Usually my father teaches me knowledge as a teacher, but one day, my father suddenly said to me, "Today, you are a teacher and I am a student." I agreed at once, but what I never expected was that my father wanted me to talk about the new math lesson "the sum of the inner angles of a triangle" that I had not finished learning. I immediately objected, "this is a new lesson, and the teacher will tell us next class!" " "Dad said seriously," Don't tremble, you must explain it to me today, or you won't want to sleep. " I read the book helplessly for a while and said to my father, "I don't understand." It depends on you. " Dad stared at me with his eyes, and the veins stood out on his neck jumped straight, as if to swallow me at once, and said maliciously, "Have you seen it ten times?" "No one can save you now, but you can only ask for help. Only when you knock down the difficulties and tell me the new lesson can you sleep. " Looking at the "devil" in front of me, I had to obediently read the textbook once, twice and three times, and kept sketching on the manuscript paper ... God has eyes, and I finally understood the new lesson. After telling it to my father, he turned anger into laughter and said to me, "Thank you, little teacher, for explaining this lesson to me." At this moment, I suddenly realized my father's good intentions. He encouraged me to think hard and cultivate my good habit of self-study and independent thinking.

Then, let's take a look at his caring face. One night near the final exam this semester, my father always accompanied me to do my homework in the study. The clock pointed to eleven o'clock, and I looked at a lot of unfinished homework. I'm as anxious as a cat on hot bricks. When my father looked at it, he handed me a piece of paper, which read: "Son, you have been really tired and bitter studying these days. Father sees it in his eyes and hurts in his heart. I hope you will be strong and overcome the immediate difficulties ... "I baked a ham in the microwave oven to replenish energy. Looking at my father's affectionate words and eating delicious ham, my eyes became blurred. I said to my father, "Dad, I am very touched." ..... "Finally, let's look at his humorous face. Dad likes to be funny, and he can perform comedy star Zhao Benshan's sketches Grass and Clown. But a joke made up by my father made me laugh my head off. He said: there was a young man who did a lot of metal work, but he was embarrassed to eat more. One day, he was eating noodles in the canteen. He ate half a catty of noodles first, but he was not full. The canteen master asked him strangely, "didn't you just eat half a catty of noodles?" "He lowered his head and said," My relatives' children are here, "but he still didn't have enough to eat, so he went to the canteen to make noodles. The canteen master was surprised and asked him, "why are you here again?" "He stammered with a red face," The child's mother is here again, "the canteen master jokingly asked him," Do you have any relatives? " He picked up the noodles and ran away quickly ... after listening to this joke told by my father, my mother and I almost "died" laughing. composition

Now, I understand more and more that my father cares about me whether he is angry, concerned or humorous. I like my father more and more.