把擴散拆成「雲團→分枝→漸散」三階段，又點名重力／密度差／對流三種物理，逼模型算出真實流體而…
Extreme close-up of black ink dropped into clear water in a glass vessel. The ink disperses in realistic fluid… [ ... 完整 prompt + 變數說明 + sample output 在原站 ]