Ages 6–12 · a serial story at bedtime

Bedtime Expeditions

A bedtime story that continues every night. The narrator remembers where the heroes stopped, and every place they discover comes out of a label printer, ready to stick on the magnetic map.

2,000–3,200 CZK (about €80–130)
about 15 minutes a night
Prusa MK4S · ESP32 · Claude

The map hangs on a magnetic board, 60 × 90 cm. The kids set their heroes on it. My 9-year-old son holds the orange button and talks for his hero, my 6-year-old daughter holds the green one and talks for hers. At a tense moment one of them throws a foam die and says the number out loud. After about a quarter of an hour the narrator walks the heroes to camp.

A new place gets a printed label with its name, an icon and one sentence about its secret. The kids stick it on a magnetic card, color it in and pin it on the map. A chronicle file keeps the heroes, the treasures and the mysteries nobody has solved yet, and the place they like most gets 3D printed on the weekend.

Who plays: two kids, with a parent sitting next to them. The parent has a third button that stops the narrator at any moment.

What runs where: a small box next to the board, our Mac at home (the Gateway), and Claude for the story itself.

Play a round

Three evenings of one expedition, cut down to a few clicks. Pick what a hero says and hold that kid’s button while they talk. Then roll the die, print the new place and pin it on the map. The red button belongs to the parent and stops the narrator at any point. Every reply here is written in advance; the real narrator makes them up on the spot.

The demo board is a drawing. The real one is a magnetic board, 60 × 90 cm.

Evening 1 of 3 · minute 0 of ~15

Narrator

mic off

foam die

thermal label printer

The wow moment

The heroes walk into a place nobody has seen before. The narrator gives it a name, the printer next to the board buzzes, and out comes a label: Owl Tower, a tiny tower and one sentence about its secret.

My 6-year-old daughter sticks it on a magnetic card, colors the tower with a crayon and pins it on the map before the lamp goes off. The next evening starts from that label.

Three weeks later the narrator asks what the brass key from the Old Well might open. Both kids remember where they found it.

A sample evening

NarratorLast time, Badger and Fox made camp under the Moss Bridge. In the night they heard a bell beyond the forest. Nobody knows who rang it.
Daughter (6)Maybe a ghost.
NarratorMaybe. Fox, the path splits. Fireflies one way, fresh paw prints the other. Which way?
Daughter (6)Fireflies!
NarratorThe fireflies lead you to a dark tower above the trees. Something big lands on its roof. Badger, roll the die and tell me the number.
Son (9)Two.
NarratorTwo. A gust from huge wings blows out the lantern. You hide in the doorway, and an owl the size of a wardrobe looks down at you.
Son (9)I show it the brass key.
NarratorThe owl turns the key over in its beak and hands it back. Not shiny enough. This place needs a name. I’ll call it Owl Tower.
label printer:
OWL TOWER · The owl at the top counts every ring of the night bell.
Mom (parent button)Teeth.
NarratorThe heroes make camp at the foot of Owl Tower. The owl wants something shiny. More tomorrow.

Written for this page as an example. At home the narrator speaks Czech.

Why a tenth time

The map growsAfter a month the board is covered with labels the kids colored themselves. Each one is a place they found on a particular evening.
Mysteries carry overThe chronicle keeps what nobody has solved yet, like who rings the bell at night. Tomorrow starts with that question.
Two heroes, two buttonsThe narrator turns to each kid in turn, so my daughter gets her scenes even on evenings when her brother has a lot to say.
The die can say noA 1 or a 2 means trouble: the lantern goes out or the floor gives way. Code reads the number, so the narrator can’t turn a bad roll into a win.
One building a weekOnly the favorite place gets 3D printed, on the weekend. The story never waits for the printer, and a building on the board means the kids picked it.

What AI adds

Claude is the narrator. Before each evening it reads the chronicle and continues from where the heroes stopped, including the mystery from three weeks ago.

It answers what the kids actually say. If my son wants to dig a tunnel under the fallen tree, the tunnel is in the story.
It turns a die number into a scene. Code decides how well the move went, and the model decides what that looks like.
It names every new place and writes one sentence of secret short enough for a label. Code checks both before printing.

A parent can run a serial story too. I would lose track of who has the brass key by the second week.

How it’s built

The narrator box and the label printer sit next to the board. Speech recognition, the chronicle and the Czech voice run on the Mac, our home server, which this gallery calls the Gateway.

Printed parts

HeroesOne figure per kid, printed in up to five colors on the MMU3. The magnet goes in during a print pause and gets printed over, and each figure is too big to swallow.
Weekend buildingsThe favorite place of the week as a small 3D building, with a magnet sealed inside the same way.
Narrator boxA case with a speaker grille, a mic hole and three buttons: orange and green for the kids, red for the parent.

Electronics

ESP32 in the narrator box, with an INMP441 microphone, a MAX98357A amplifier and a speaker.
Three buttons: one for each kid and one for the parent.
A thermal label printer for the place labels.
On the Mac: whisper.cpp for speech to text, Claude with rules for kids and the chronicle in a file, and Piper with a Czech voice.
No electronics at all: magnetic foil cut into cards, and the foam die.

Parts list

Part	Used for	Price
Magnetic board 60 × 90 cm	the map	~1,000 CZK (about €40)
ESP32, INMP441 mic, MAX98357A amplifier, speaker, 3 buttons	narrator box	up to 500 CZK (about €20)
Thermal label printer, magnetic foil, foam die, magnets, filament	labels, cards, die, heroes	500–1,700 CZK (about €20–70)
Mac (the Gateway), Prusa MK4S with MMU3	already at home	0 CZK
Total		2,000–3,200 CZK (about €80–130)
Claude	the narrator, running cost	tens of CZK a month

The estimate gives the total and two items: the board at about 1,000 CZK and the modules at up to 500 CZK. The third row is what is left of the total, and most of it is the label printer.

Architecture

Where code ends and the model begins

Code does

Opens the mic only while a button is held, and knows whose turn it is.
Keeps the chronicle file: heroes, camp, treasures, open mysteries, places.
Reads the die number from the transcript and decides how well the move goes.
Ends the evening after about 15 minutes and asks for the camp scene.
Checks every label before printing: name length, icon from the list, one sentence, blocked words.
Stops everything when the parent presses the red button.

The model does

Tells the story in the narrator’s voice, from the chronicle and from what the kids just said.
Turns the die result that code picked into a scene.
Names new places, picks an icon from the list and writes the one-sentence secret.
Writes the camp summary that code saves into the chronicle.

Safety and offline

Voices stay home: whisper.cpp turns speech into text on the Mac, and Piper speaks the narrator’s lines on the Mac. Claude only ever gets text.
Mic on a button: The mic records only while a kid holds their button. The red parent button stops the narrator mid-sentence.
Code keeps the rules: Turns, the die, the 15-minute limit and the chronicle live in code. Claude picks icons from a fixed list, and code checks every label before it prints.
Nothing to swallow: Magnets are sealed inside printed figures and buildings. The box runs from a USB charger, so there are no coin cells anywhere. The cards are flat magnetic foil and the die is foam.
A parent’s account: Claude runs on my account with rules for kids. Anthropic’s terms allow products for minors when safeguards are in place.
Without internet: No internet means no narrator. The board, the labels and the die still work, a parent can take over the story, and the chronicle is a plain file on the Mac.

Roadmap

one eveningFirst playable prototypeA map on wrapping paper, heroes borrowed from toys we already have, and a script on the Mac that listens only while someone holds the spacebar. The parent writes new places on sticky notes. The narrator, the chronicle and the recap of last night are already there.
nextNarrator boxThe ESP32 box with the mic, the speaker and three buttons replaces the spacebar, and each kid gets a button of their own.
thenFull versionMagnetic board 60 × 90 cm, thermal label printer, magnetic cards, printed heroes and a foam die. The favorite place of the week becomes a 3D building.

More ideas to try

The map as a remote. A chip under each place card and a reader in the narrator box. At the start of the evening a kid takes a place off the map and touches it to the box, and the narrator picks up from what happened there last time.
A backpack of finds. Things the heroes find get printed as labels on bigger magnetic cards and go into each hero’s backpack at the edge of the map. At a tense moment a kid can use an item instead of rolling: the move works, but the item gets used up or changes, like a rope that snaps. Items can be lent between heroes.
A wish for each hero. Each kid says what their hero wants most, like finding a lost brother or a horse of their own, and the chronicle keeps it. Code makes sure each hero gets one step closer about every third evening, and after five steps the wish comes true. The place where it happens becomes that weekend’s 3D building.

Status: an idea. Nothing on this page has been built or tested yet, and the demo is a simulation with pre-written answers. Prices are estimates from Czech shops in October 2026.