How does Polly Horvath use imagery in Everything on a Waffle?

Example of Imagery:

"Later, as I lay in the dark, looking at the one star that shone through my window, with my foot throbbing ... worried about how I would be taunted at school if the rumor was that I was suicidal, I felt a little rush of joy. I didn't know where this joy came from. It didn't seem to need parents or ten toes or the things you think you need. It seemed to have a life of its own."