One page: buyer, problem, why now, offer, price, channel. The whole idea, defensible, on a single screen.
The exact test to run, with the pass line and the kill line set before you start — so the result isn't up for debate.
The thing you give away to prove the value before you have a product to sell.
Acceptance criteria, what must be nailed, and what is explicitly out of scope for v1.
Ten minutes, no product required
Free, in your browser, on your own key. Type it, paste your notes, drop in a .md, .txt or PDF — or say it out loud.