Great quote!

This website says:

"Without warning, coming as a complete and unexpected shock, she felt a pressure she had never imagined, as though she were being completely flattened out by an enormous steam roller. This was far worse than the nothingness had been; while she was nothing there was no need to breathe, but now her lungs were squeezed together so that although she was dying for want of air there was no way for her lungs to expand and contract, to take in the air that she must have to stay alive. This was completely different from the thinning of atmosphere when they flew up the mountain and she had had to put the flowers to her face tobreathe. She tried to gasp, but a paper doll can't gasp. She thought she was trying to think, but her flattened-out mind was as unable to function as her lungs; her thoughts were squashed along with the rest of her. Her heart tried to beat; it gave a knifelike, sidewise movement, but it could not expand.

"But then she seemed to hear a voice, or if not a voice, at least words, words flattened out like printed words on paper, 'Oh, no! We can't stop here! This is a two-dimensional planet and the children can't manage here!'"