The certificate

The certificate is the reward: a title, a message and an optional image, encrypted with a key built from every word of the event, in day order, joined by single spaces.

Write and seal it

The keeper writes events/<event>/final/final.yaml:

title: You made it through the longest night
message: >
  Seven doors, seven words, one key. Thank you for playing.
image: medal.png      # optional, next to final.yaml

Optional extras: subtitle (a line above the name), signature (a sign-off at the bottom), image_position (top to put the image where the logo goes) and background (an image behind the whole certificate). See the final.yaml reference.

Then, once every day is sealed:

advent keeper seal 2026

The words are read from the days’ source copies (it needs the editors key), so nobody retypes them. Sealing refuses while any day is missing. If a day is re-sealed later with a different word, advent verify reports the certificate as stale: seal it again.

Rewards

Finishing can unlock more than the certificate: files to download and links, listed under the certificate once it is unlocked.

rewards:
  - label: Wallpaper pack
    file: wallpapers.zip
  - label: Bonus puzzle
    url: https://example.com/secret-bonus

Files are encrypted one by one and only downloaded when the player asks for them. Everyone who finishes gets the same rewards, so a code that must be unique per person (a gift card, for instance) does not fit here. See the final.yaml reference.

Preview it

advent preview --all-open --solved

opens the calendar on your machine with every word already collected: type any name in the certificate panel to see the real certificate and download the PNG.

What players get

When every word is collected, the player enters a name and the certificate opens in the browser. It shows your brand, the player’s name, the edition and its year, and can be downloaded as a PNG. It does not show hints used or attempts: those live in the player’s browser and could be reset, so they would prove nothing.