Digital advent calendar with doors that open by date

Decide what's behind the doors

Write all 24 before you build, because the content shapes everything else. A few common kinds:

Family and friends: A memory, a photo, a joke, a clue for a treasure hunt in the house, a short message from someone far away.
Classrooms: A puzzle, a fact, a short maths problem, a winter word with its meaning. Mix difficulty so every pupil gets some days right.
Shops and brands: A tip, a recipe, a behind-the-scenes note, an offer code for that day. Make sure every offer is real and its terms are clear.
Charities and clubs: A story of one person helped, a volunteer's thank-you, one small action readers can take that day.

Keep each door's content short. Something that takes ten seconds to enjoy brings people back tomorrow; a long article behind every door doesn't.

How doors unlock

The usual rule: door 1 opens on 1 December, door 2 on the 2nd, and so on. A few decisions to settle:

Late visitors. Someone arriving on the 10th should be able to open doors 1 to 9 too, so they catch up.
Locked doors. Tapping a future door should show a gentle message ("Come back on the 14th") rather than nothing.
Time zone. The app uses the visitor's device clock, so the door opens at midnight where they are.
Opened state. Opened doors stay open, with their content a tap away, and are remembered in that browser between visits.
After Christmas. Decide whether all doors stay open into January or the calendar shows a closing message.

An honest note on cheating

Because unlocking runs in the browser, someone who changes their device's date can open doors early. For a family calendar that doesn't matter. For a daily offer code it might: treat codes as ones you're happy for a determined person to find early, or simply publish the content behind each door on its day instead.

Design that makes it feel like a calendar

Shuffled door numbers, as on a paper calendar, with door 24 larger.
An opening animation, a door swinging or a paper flap folding back, that's skipped for people who ask their device for reduced motion.
Today highlighted so nobody hunts for it.
Sound only if asked for, and off by default.
Big tap targets for children and phones.

Building it with Anticode

Give the content and the feel: "A digital advent calendar for our bakery's newsletter readers. 24 doors, shuffled, door 24 large. Behind each: a baking tip or a recipe card written below. Doors unlock by date from 1 December; earlier doors stay open for late visitors. Opened doors remembered. Warm red and cream, a paper-flap opening animation. A newsletter sign-up under the calendar."

Anticode writes it as one app. To test the unlocking before December, ask for the start date to be set a few days back while you check the doors, then ask for the real date again before you publish. If you'd rather change the door content from the dashboard without a rebuild, ask for it to come from a CMS collection with one entry per day.

A newsletter or enquiry form in the calendar sends sign-ups to you through Anticode's form pipeline; a sign-up needs an email address. That's the usual reason a business runs one: see newsletter signup page for the wider set-up.

Limits

One device each. Opened doors are saved in each visitor's own browser. Open it on a laptop and the phone doesn't know.
No prizes drawn. It can't run a fair daily prize draw or check who has opened what, since apps don't share data between people.
No personalised calendars by link. Everyone with the link sees the same calendar. To make one for a single person, build a separate app for them.
Anyone with the link can open it. Don't put anything private behind a door.

For a single countdown to a date, the countdown timer app is simpler. For a gift exchange, see the secret santa generator.

Questions people ask

Can I use it for something other than Christmas?

Yes. Any countdown works: 30 days to a wedding, a Ramadan calendar, a week before a launch. Give the start date and the number of doors.

Can I put photos behind the doors?

Add your own photos with the build and say which door each belongs to. Images from other websites can't load inside the app.

Can children use it without an account?

Yes. Nobody signs in, and nothing they open is sent anywhere.