The only way to know what someone feels is to ask them
Not to read their face. Not to guess from outside.
Think of a time someone was smiling and they were not happy. You have seen it. You have probably done it. Now think of a time someone said "I am not angry" while everything in your observation said they clearly were.
Both happen constantly, at every age. Sometimes we cannot know what someone feels from the outside. Sometimes they do not know it from the inside. That is not a flaw in people. That is part of being human, and it is where this program does its work.
So the deepest rule in the program is also the simplest one. When you want to know what someone feels, ask them.
Children practice this inside the games. After every round of charades, the guessing stops and someone asks the actor what they actually felt. A guess that does not match is not wrong. It is a different true reading of the same body. Children learn that guessing is interesting and asking is how you know.