I am not a native English speaker. I don't quite understand why the phrase is "you don't look your age" instead of "you don't look like your age" or "you don't look like you are at your age."
I understand that "you don't look your age" means you look younger than people at your age. Just I don't understand how come the meaning of "look" is different from its usual meaning which is to stare / gaze / watch something.