It appears to be Doritos!

Wei Wuxian gets his own package of Cheeze-Its. "Not even stale."

"Lucky!" She eats a Dorito. "It's a bit stale, but the flavour's still good. That's the important part."

"Wanna swap?"

"If you want to, but I am happy with this."

He drops half his Cheez-Its in her hands.

That is. So many cheez-its. A bounty of cheez-its. She would hand over some Doritos as a trade except her hands a full of cheez-its. "Thank you."

"--oh, you don't know anything about magical theory!"

"...no!"

Does she want an INFODUMP about MAGICAL THEORY, the MOST INTERESTING SUBJECT IN THE WORLD

Too bad she's getting it whether she wants it or not.

Wei Wuxian is very good at infodumps. She listens attentively.

They should sit down over here (he sweeps for mals first) and then he can draw diagrams to help explain the concepts to her.

Unfortunately, to get close enough to see the diagrams, they're also close enough that their legs are pressed together and his arm could very easily go around her shoulder.

So this is very educational but also a teensy bit alarming. What is she meant to do? Is she meant to put arms over shoulders? Hopefully not??? She is going to listen and sit very, very still

He casually slings his arm over her shoulder while discussing the theory of mana capacity.

Okay so this is happening.

...arms on shoulders are nice.

Wei Wuxian doesn't seem to find arms on shoulders to be remarkable or interesting in any way, particularly compared to diagrams about magical theory!

"We should really have a magical theory class. I bet that's going to be way more useful than Romance of the Three Kingdoms."

"It does seem a whole lot more practical."

"Why do all the spell classes have to be themed around the liberal arts."

"Maybe it's to motivate the students?" Chu Chu has maybe a skewed view of how teens feel about school work.

"Like, we're never going to learn about military history unless it's the only way to get spells to set mals on fire?"

"I was thinking the other way around, but your way makes more sense."

"I like military history, si-mei, but I have to say I'm much more motivated to learn how to set mals on fire."

"It's definitely more useful in the Scholomance than knowing how to make a phalanx."

"You could make a phalanx during graduation."

"Would that even help much?"

"No idea, we haven't gotten to phalanxes yet."