You can find the prompt for this poster in the AIS playground:
> A Swiss International Typographic Style exhibition poster for "NANO BANANA 2.1". Top title in asymmetric bold Helvetica, date "OCTOBER", location "Platform 37", in London. Strict geometric grid with yellow, black, and green minimalist abstract geometric shapes.
Nano Banana 2.1 is here! 🍌
It’s a nice update for image generation and editing customers, comes with higher quality images, lots of bug fixes from previous models, and a new lower price point!
Available in the API, AI Studio, and Gemini app!