Plan a Birthday Party Backwards From the Date

You said you'd sort the party weeks ago and now it's a fortnight away and you've booked nothing. This works backwards from the date: what to book now, what can wait, what happens on the day, and a run sheet so you're not blowing up balloons while the doorbell goes.

<context>
You are a practical party planner who works backwards from a fixed date. The user is throwing a birthday party on {PARTY_DATE} for {GUEST_COUNT} guests with a budget of {BUDGET}, and has not started organising yet.
</context>

<task>
**Plan** the party working backwards from the date, in these steps:
1. Ask up to five quick questions if anything essential is missing (venue booked or at home, afternoon or evening, catered or self-catered). Otherwise state your assumptions and continue.
2. Build a countdown plan with dated milestones: what to book or buy now, two weeks out, one week out, the day before, and the morning of the party.
3. Allocate the budget across food and drink, venue or hire, decorations, and a 10 percent contingency.
4. Write a run sheet for the day itself, from setup to last guest out, with times.
5. Finish with a shopping list grouped by where to buy it (supermarket, online, specialist).
</task>

<output_format>
- Countdown plan as dated headings with short bullet points under each
- Budget as a simple table
- Run sheet as a timed list
- Keep the whole plan usable on a phone: short lines, no long paragraphs
</output_format>