Castle Lab
Every part of a castle was built because an attack had worked: the moat against siege towers, the gatehouse because the gate was the weak point, round towers because square corners could be dug out from under. Castle Lab lets students build a castle in 3D, from a Norman keep to a Japanese castle or a sandcastle, test it against six kinds of siege, walk inside it, and print it as a cardboard model.
Using this with a class? Make a free class and add your students yourself: each gets a username and password, with no email or Google account needed. Or give them one join code. Using Google Classroom? Post the link there; with a free class, the link also puts each student in your class, so you see their work. mytekDev is also available from the Google Workspace Marketplace, so your school's Google admin can install it for everyone.A first lesson: Everyone starts from the same plain castle, which loses to every attack. Each student adds one part at a time and tests it, then the class compares which part did the most, and why.
Set up a free class Share to Google ClassroomWhat a student actually does
They open the lab on a Norman keep, 45 meters by 41, with walls 171 meters round. They pick another style, a fairy tale castle with tall blue cones or a Japanese castle with stacked roofs, and change anything: three to eight corners, how high and thick the walls are, the battlements, the stone, round or square towers and their roofs.
On the Layout tab they drag the corners of the plan by hand, move the gate to another wall, and place the keep, the hall and the well. Every wall shows its length, and the readout under the castle gives the perimeter and the courtyard's area.
On the Siege tab the castle is tested against ladders, a siege tower, a battering ram, diggers under a tower, a trebuchet and a long siege. Each test says held, shaky or fell, and why. Then they press Walk and go in through the gate, up onto the wall walk and to the top of the keep.
Will it hold? Each test says what happened and why, and offers a part to try. Adding a well turns the long siege from fell to held.
What they are learning while they play
Nothing here is presented as a lesson. This is what the activity is made of.
| What the student does | What it is |
|---|---|
| Adds a moat and sees the siege tower stopped | Cause and effect in history. Each part of a castle answered an attack that had worked. Testing one part at a time shows which attack it was for. |
| Drags the corners of the plan and reads the wall's length | Perimeter and area. The same length of wall can hold very different amounts of room. A square holds more than a long thin rectangle with the same wall. |
| Changes one thing, tests, and keeps or undoes it | The engineering design process. Testing one change at a time is how you know what each change did. |
| Prints a castle at 1:200 | Scale. Every length is divided by the same number, so the model has the castle's shape at a size that fits on a desk. |
How to tell whether it landed
Ask, and let them show you. A student who has understood it can answer these without help.
- What was a portcullis for, and what attack did it help against?
- Why does a moat stop a siege tower but not a long siege?
- Your plan has 140 meters of wall. How could you make the courtyard bigger without more wall?
- Which one change did the most for your castle in the siege test? Show me.
Use it in your subject
Not a technology class? Then the app is how students show what they learned in your unit. More projects for every subject.
History
Start everyone from a plain castle that loses to every attack. Add one part at a time and record which test it wins, then match each part to the attack it was built for.
Math
Find the perimeter and area of a 40 by 30 meter castle by hand, then drag the plan into new shapes with the same wall and compare the room inside.
Engineering
Give a brief: hold against five of six tests, with walls no taller than 15 meters and no more than five features. Students test one change at a time and defend their design.
Art and design
Print the castle as a cardboard build kit and build it, or design a crest for its flags and banner.
Practical notes
- AgesAges 8 through high school. Younger students pick a style and add parts; older ones draw their own plans, work the math by hand and design to a brief.
- TimeA minute to a castle of their own. A satisfying session is thirty to forty-five minutes.
- EquipmentA computer or Chromebook with a modern browser. The castle is 3D, so a very old or very slow computer may struggle. Nothing to install.
- CostFree. The app has no paid tier.
- PrepNone. Open the page and go. Reading this page first takes about three minutes.
- In a groupEveryone can start from the same castle, then compare what each student changed and how it tested.
For co-ops, microschools, and classrooms
Give pairs the same weak castle and a limit of five features. Each pair designs, tests and defends their castle; then print the strongest as a cardboard model and build it together.
Common questions
Is Castle Lab free?
Yes. It runs in your browser and there is no paid tier. A free account adds saving and sharing, but nothing on this page is behind a paywall.
Does my child need an account to try it?
No. The demo on this page is the complete lab with a Norman keep. Make a free account to save a castle and share it.
Which castles can it make?
Thirteen styles to start from: a motte and bailey, a Norman keep, a concentric castle, a crusader castle, a fairy tale castle, a chateau, a Japanese castle, a desert fort, a tower house, a brick Gothic castle, a sandcastle, an ice castle and a dark fortress. Each one can be changed, so students can make castles that are not on the list.
Are the siege tests accurate?
They are the app's simplified rules, drawn from what historians write about sieges, and the app says so. They show what each part of a castle was for; they do not predict the outcome of a real battle.
Can we build it for real?
Yes. The Export tab prints a cardboard build kit at a model maker's scale, with a page that says how. It also saves a picture, a floor plan, a file for a 3D printer and a 3D model for a game.
Still have a question? Ask us, and a person will write back.
Where to go next
Start with Castle Lab
Trying it costs nothing and takes about five minutes. An account is what makes the work last.
Castle Lab is one of the making apps on the platform. It is a place to make things, not a course, and it is not a substitute for a teacher: it is at its best when an adult asks the questions above and takes the answers seriously.
Page last reviewed November 2026.
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