Put something in the tin

Nothing. No account, no badge, no faster analysis, no feature that was hidden before. There is deliberately nothing to hand over, because there is nothing being withheld.

Saying so plainly matters more than the money. A donation laid out like a purchase — tiers, a menu of amounts, a list of what each one unlocks, a monthly box already ticked — tells you that you are buying something, and you would be right to expect it. That is why there is one button and no options: you are not buying anything here.

Grading a game costs nothing to serve — Stockfish runs on your own processor, so the hundredth game is as cheap as the first. What is not free:

• Bandwidth. The engine is about seven megabytes, sent to every visitor who has not been here before.
• A domain, and whatever hosts it. Small, but not nothing, and it arrives every month whether anyone visits or not.
• Time. The unglamorous half — the opening book, the contrast audit, the thresholds that stop the pattern miner from making things up.

The button takes you to a page Stripe hosts, on Stripe's own domain, and the card details are typed there. It is one charge — nothing is stored for later and nothing renews. If you want to choose the amount, you choose it there.

This app has no server and never sees your card. It could not store a card number if it wanted to; the same reason your games are never uploaded applies here, only more so.

Then do not, and nothing about the app changes. Telling somebody about it, or opening an issue when a move is graded wrongly, is worth a good deal too.