The instrument

This is the hook, drawn. Push the imbalance and watch what a swap would pay. When the pool is live it reads the real one instead, and you can still take the dial off it.

• The heap in the glass leans toward whichever side the crowd is on. That lean is the imbalance the hook measures.
• Piling onto the crowded side pays the premium. Relieving it pays nothing extra, at any imbalance.
• The curve is the whole rule: premium rises linearly with imbalance and stops dead at 3%.
• Whatever is charged is donated into the pool in the same transaction, so the column marked goes to the LPs is the same number as the one you paid.