First, create a SPEC.md file in the repo root with a basic outline:

Spec

Overview

[To be filled via interview]

Target Audience

[To be filled via interview]

Key Messaging

[To be filled via interview]

Page Sections

[To be filled via interview]

Design Direction

[To be filled via interview]

Technical Decisions

[To be filled via interview]

Open Questions

[To be filled via interview]

Then read the SPEC.md and interview me in detail using the TodoAskUserQuestionTool about literally anything: technical implementation, UI & UX, concerns, tradeoffs, positioning, copy, audience, etc. But make sure the questions are not obvious.

Be very in-depth and continue interviewing me continually until it's complete, then write the final spec to the file.