ベクトルの共変・反変を直感的に理解

I found a book that gives an intuitive explanation of the covariance and contravariance of vectors, making you say, "Ah, so that's what it means." I have summarized that part. It was the easiest to understand of all the books I have read so far. "Vectors and Tensors for Physics" by Daniel Fleisch, published by Iwanami Shoten.