* "To make a long story short" - Meg Murray uses this phrase to summarize events for Charles Wallace. This is a very common idiom that means to skip over unnecessary details and get to the point.
* "It's not the end of the world" - This phrase is used by Meg to comfort Charles Wallace, implying that even though things are difficult, they can still be overcome. This is a common expression used to reassure someone in a stressful situation.
* "A piece of cake" - This idiom is used by Meg to describe how easy it is to travel through time and space using the tesseract. While not explicitly stated, the implication is that it is so simple that it's like "a piece of cake."
* "He's a real chip off the old block" - This idiom is used to describe Charles Wallace's resemblance to his father. While not stated in the book, the implication is that Charles Wallace is very similar to his father in terms of intelligence and personality.
* "A storm in a teacup" - While not directly used, the imagery of the "Black Thing" engulfing the world could be interpreted as a metaphorical "storm in a teacup." This idiom refers to a situation that seems very serious but is actually insignificant.
* "To be in a pickle" - This could apply to the situation of the children being trapped in the dark and oppressive world of Camazotz. They find themselves in a difficult and challenging situation, which could be described as being "in a pickle."
It's worth noting that the novel uses a lot of symbolism and allegorical imagery, which can be considered figurative language, but may not fit neatly into the category of "idioms."
Let me know if you'd like to explore some of those figurative language elements!