Look at shapes A and B. Are they the same size and shape?
The answer, surprisingly, is yes. To most people, shape A appears to be shorter and wider than shape B. But it’s just a matter of alignment; shape B is aligned further to the right than shape A.
Despite knowing they are the same exact shape and size, your brain may still be having trouble perceiving them that way. If you were to print the 2 shapes out on paper and cut them out, you could see that they are exactly the same in all dimensions. Or, you can simply view shapes A and B with parallel red lines superimposed on them, and it’s easy to see that they are misaligned.
Because the leftmost diagonals of the shapes are in a continuous line, our brains subconsciously follow that line and perceive that the two shapes are sitting on top of one another. But in reality, one is just slightly shifted on the horizontal axis.