Toy Workshop · Concept

Runes

Invent a spell, print it as a rune and give it to your sister. It will work for her too.

Ages 6–12
Parts ~2,260 CZK (about €90)
Idea stage · not built yet

1The Book. An open-book stand, 220 × 160 × 60 mm, printed in leather brown with gold edges. ESP32-S3, microphone and speaker inside.
2Two rune sockets, Ø 32 mm, each with an RC-522 NFC reader underneath.
3Thermal printer in the spine. Spell cards come out the top.
4The wand, 280 mm. ESP32-C3, motion sensor, vibration motor and a 400 mAh battery in the handle.
5Translucent PETG tip over a single WS2812 LED.
6Runes, Ø 30 × 5 mm. Raised symbol, NTAG215 chip sealed in mid-print.

A child tells the Book what a spell should do. Claude turns the sentence into a small rule, the Book reads it back, and overnight the 3D printer makes a rune: a 30 mm token with that rule stored in an NFC chip sealed inside. Set the rune on any Book and wave the wand. The spell runs without Wi-Fi or the model, even at a friend’s house, as long as the friend has a Book too.

The wow moment

Her spell, his room

My 6-year-old daughter hands her big brother a small green stone with a spiral on top. “This is my spell. It’s called Fireflius.” He sets it on his own Book, circles his wand twice, and his room goes her shade of blue while her wind chimes play. “My spell works at your place too!”

Nothing was paired or synced. The rule was in the stone, and his Book read it.

That scene needs two Books and two wands in the house. The parts list further down is for one set.

Fireflius

Made by Little sister (6)
Element air · power 4

{"v":1,"n":"Fireflius","by":"sister",
 "el":"air","pw":4,
 "when":{"wand":"circle_x2"},
 "do":[{"room_light":"blue"},
       {"play":"wind_chimes"}]}

What the NTAG215 inside holds · 135 of 504 bytes

What it sounds like at the Book

From the design notes. The model’s job is the JSON and the names. Whatever the Book says about what a spell does is built by code from the rule itself, so it can’t promise something the rune won’t do.

Little sister“I want it so when I wave my wand up and down, the lamp twinkles like a little star and plays that song with the raindrops.”
The Book“Got it. When you wave up and down, the lamp in your room blinks white three times and Raindrops plays. Do you want to give this spell a name?”
Little sister“Stardrop!”
The Book“Stardrop is written down. Your rune will be ready tomorrow morning. Now show me the wave three times.”
Combining Stardrop + Fireflius
The Book“These two go together, both are cast with the wand. The new spell blinks blue and white and plays both tunes, one after the other. I’m calling it Starry Firefly. Shall I print it?”
An incompatible pair
The Book“One spell turns the light on and the other turns it off. Together they’d just argue. Try a different pair.”

How it plays

From a sentence to a duel

The child tells the Book what the spell should do. The Book is a stand shaped like an open book, with two rune sockets, a microphone and a printer.
Claude turns the wish into a rule in a tiny language with a whitelist (trigger → action). Code checks it, and the Book reads it back.
The child performs the wand gesture three times, and code stores its pattern.
The Book prints a spell card, and overnight the 3D printer makes the rune, a 30 mm token in MMU colors with an NTAG215 chip sealed inside. The whole rule is stored on the chip as JSON of up to 504 B.
A rune set in the Book’s socket charges the wand. The wand holds three spells at a time.
To combine two spells, put one rune in each socket. Code checks that they fit (same trigger type, no conflicting actions, at most 4 actions), Claude names the new spell, and the pair gets printed as a new rune.
In a spell duel, each sibling brings three runes and they cast in turns. The room lights show who is ahead.

Try it

The Book on your screen

Three stations, in the order a kid meets them. Make a spell by talking, combine two runes on the Book, then charge the wand and cast in big brother’s room. The model’s answers here are pre-written. The checks are plain code, the same kind the Book would run.

Speak a spell

Pick a wish. At home you’d hold the gold button on the Book and say it out loud; the microphone is only on while the button is down.

The Book is waiting. Pick a wish on the left.

Combine two runes

Tap a rune to drop it into a socket (dragging works too). Tap a socket to take the rune back. Code checks three things; if the pair fits, the printer does the rest.

Checked in code, no model
Same trigger type
No actions that fight each other
At most 4 actions together

The BookPut a rune in each socket.

Chip, left socket

// empty

Chip, right socket

// empty

The spell card for a new pair comes out here.

Charge the wand and cast

Tap runes to charge the wand (it holds three), then pick a gesture. The wand only knows the gestures of the spells it carries. The room belongs to big brother; most of the runes don’t.

It’s after 8 pm Sound (plays only when you click)

// code log: charge the wand, then cast

Why a tenth time

A collection that keeps growing

Runes get collected, given away and traded like cards, except every one of them was invented by a kid in the house. Two runes can make a third, so the shelf grows like a family tree. Some pairs refuse to combine, and you only find out which by trying.

The spells don’t expire either. A rune printed in October still works in March, on any Book.

Spell duels give siblings a contest. Each brings three runes. Code gives every spell an element and a power level from a fixed budget, so nobody can print the one rune that beats everything, and the room lights show who’s ahead. In the demo above, power is 6 minus the number of actions, so a spell that does four things hits softer than one that does one.

What’s new thanks to AI

A six-year-old writes a program by saying it

She says a rule in her own words, and a minute later it is safe, runnable code sitting in a stone on her shelf.

She says“When I wave up and down, the lamp twinkles like a little star and plays the raindrop song.”

Claude returns

{"when":{"wand":"wave_updown"},
 "do":[{"lamp":"blink","color":"white","x":3},
       {"play":"raindrops"}]}

Code checks it, the printer makes itStardrop. 153 bytes on the chip, readable by any Book.

Without a language model you’d need a menu of presets or block programming, and a kid who is still learning to read won’t get far with either. Here the model has one narrow job. It turns the sentence into a when → then rule from a closed list of events and actions, and it makes up names.

Code checks the rule against the list, and the Book reads it back in plain words so she can say “yes” or “no, the other lamp”. She learns that a program is something you check before you run, and nobody had to use the word program.

The step up from the Rule Box, an earlier round-1 idea, is that the program becomes a physical object that carries its own code. You can give it away, combine it with another one, and run it with no network.

How it’s built

Three printed parts, a few cheap boards

Everything prints on a Prusa MK4S, with the MMU3 doing the second color: gold on the Book, the spiral on the wand, the symbol on each rune.

The Book

About 220 × 160 × 60 mm, shaped like an open book, in leather brown with gold ornaments. Two Ø 32 mm sockets sit over two RC-522 readers (dashed), the ESP32-S3 goes under the left page, and the thermal printer lives in the spine.

The wand

280 mm, hollow, with a two-color spiral from the MMU. The translucent PETG tip spreads the light of one LED. The battery sits in the handle behind a cap held by an M2 screw, so small fingers stay out.

The runes

Ø 30 × 5 mm with a raised symbol in a contrasting color. The print pauses, an NTAG215 goes in, and the last 1.5 mm of plastic seals it. The pause means a grown-up has to be awake for one minute of an otherwise overnight print.

Why NTAG215: the rule itself lives on the chip, and it has 504 bytes of user memory. The cheap NTAG213 stickers hold 144 bytes, which is tight for a rule with a name and two actions and too small for a combined one.

Parts list

Part	What it’s for	Where	CZK
ESP32-S3 DEVKit	the Book’s brain	LaskaKit	448
RC-522 NFC reader ×2	reading and writing runes in both sockets	GME	98
NTAG215 tags, 10 pcs	one inside every rune	estimate	~120
INMP441 microphone	push-to-talk	LaskaKit	98
MAX98357 amp + 40 mm speaker	the Book’s voice and the spell sounds	LaskaKit, GME	187
CSN-A2 thermal printer	spell cards	LaskaKit	928
ESP32-C3 SuperMini	the wand’s brain, BLE to the Book	estimate	~100
GY-521 (MPU6050)	wand gestures	GME	79
Vibration motor	the “click” when a spell fires	GME	49
Li-Po 400 mAh + TP4056	wand battery and charger	battery estimated	~120 + 20
WS2812, 1 pc	the glowing tip	estimate	~10
Total for one Book and one wand			~2,260 CZK (about €90)

Prices from Czech shops on Sep 24, 2026. Not in the total: filament, a push button, BPA-free thermal paper, a 5–9 V / 2 A supply for the printer, and the second set if both kids get a Book.

Architecture

Swipe sideways for the whole diagram →

Where code ends and the model begins

The model does

turns the child’s sentence into a JSON rule, with a schema that only offers the listed triggers and actions
invents names for new spells and combinations
words the friendlier lines, like an offer when a wish isn’t allowed

Code does everything else

checks every rule against the whitelist again, schema or not
builds the read-back sentence from the rule itself
writes and reads the chips
decides whether two runes fit: same trigger type, no actions that fight, at most 4 actions
assigns element and power from a fixed budget, runs duels, keeps score
recognizes gestures and runs spells with no model at runtime
enforces the 8 pm quiet rule

Actions come in two tiers. Wand actions (light, vibration) work anywhere. Room actions only work at home, and only on a whitelist of kids’-room devices in Home Assistant. Sounds come from the Book’s speaker; the wand has none.

Safety and offline

What it won’t do

Saved spells run offline, for good. The rule lives on the rune, so it also works at a friend’s house, as long as the friend has a Book and a wand.
The whitelist has no locks, no heating and no other rooms. Room actions only reach the kids’-room devices listed in Home Assistant.
Parental time lock: after 8 pm, quiet spells only.
The microphone is on only while the button is held. The Book doesn’t listen in the background.
A parent approves each overnight print with a tap on a phone notification.
API keys stay on the Gateway, a Mac at home. They never go into the ESP32 in a kid’s toy.
Ø 30 mm runes are just under the EN 71-1 small-parts cylinder (31.7 mm), so they are for kids 6+ and not for siblings under 3. For younger ones, print the Ø 35 mm version.
The wand battery gets a protected charger (TP4056 with DW01) and a compartment closed with a screw. Thermal paper should be BPA-free.

Roadmap

From stickers to duels

Protoa weekendThe Book with one reader and wand-only rules. No printed runes yet; plain NFC stickers stand in for them.
v1a monthPrinted runes with the JSON on the chip, Home Assistant actions for the room, the card printer.
v2after thatCombining runes and spell duels.

Scores, v2 of the idea

9Novelty

9Engagement

7Feasibility

Compared with v1, a spell is now a portable physical object with its code inside, which brought in collecting, gifting, combining and duels.

Status: an idea. Nothing on this page has been built or tested yet, and the demo above is a simulation with pre-written model answers. Prices are from Czech shops on Sep 24, 2026; the ones marked as estimates are guesses.