Write a window poster people read from across the street

Help me write a window poster people can read from across the street.

What it's for: [e.g. an offer, an event, now open Sundays, we're hiring]
Where it'll go: [e.g. shop window, A-board on the pavement, café noticeboard]
Size: [e.g. A3, A2]
How far away most people will be: [e.g. across the road, walking past]
What I want them to do: [e.g. come in, book, remember the date]
Must-have details: [dates, times, prices if you're happy to show them]

Ask me up to 2 short questions first. Wait for my answers.

Then:
1. Three headline options of 5 words or fewer.
2. The full poster: headline, one supporting line, the key detail, and the call to action, nothing more.
3. Which part should be biggest, and which can be small.
4. A version for an A-board, if it's different.

Fewer words is better, UK English.

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