Recently, I have been mining the Polymarket API

and found that many concepts in prediction markets are very interesting.

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For example, a few days ago I was asked
why the order books for Yes and No are mirror images of each other.
I was momentarily at a loss for words, thinking it was an intuitive thing,
but how do I explain it to others?

At the time, I tried a few explanations,
but it seemed like the other person didn't quite understand.

Like an analogy:
Perpetual contract trading can
open long, open short, close long, close short.
Open long = close short are both market buys.
Open short = close long are both market sells.

Or using the underlying principle of the entire prediction market:
For each event, a Yes/No pair is generated.
So when you buy a Yes token,
it's equivalent to minting a Yes/No pair first,
then selling the No.

But it seems none of these directly explain the mirror image issue.

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If I can't teach others, it means I still don't understand 🥲