Every curious child deserves a chance to try.
Rangkai was born from a simple question: how can anyone in Indonesia, in cities or villages, learn to make a blinking light, a sensor that reads temperature, or a small robot, without needing a lab first?
It began with a wish, then came together piece by piece
We saw many children and teachers who wanted to learn electronics and programming but stopped before they could even try. Not because they couldn't, but because the path was too expensive, too intimidating, or too unfamiliar.
That's where the wish came from: a breadboard that opens in any browser, speaks Indonesian, has levels from kids to experts, and doesn't punish you for mistakes. We started with one LED and one button, then added components, a block editor, classes, assignments, and quizzes, one at a time, always asking: does this help people learn?
We chose the name Rangkai, Indonesian for "to assemble", for three reasons: assembling components into devices, assembling ideas into creations, and helping today's children become tomorrow's technology makers.
The barriers we want to remove
- 1A set of components and a microcontroller board isn't cheap, and not every school has a lab.
- 2Components that burn out from a wrong connection make many people afraid to try again.
- 3Good simulators are mostly in English and made for adults who already know the basics.
- 4Teachers have to check dozens of circuits one by one, leaving less time to guide students.
Six things we won't compromise on
Mistakes are part of learning
In Rangkai, LEDs can burn out and wires can be swapped. Only the picture breaks, and the message explains what happened.
In our own language
Messages, hints, and component explanations are written in plain Indonesian, from kids' level to advanced.
For everyone
Students learn for free. All you need is a browser and internet, with nothing to install.
Keeping children safe
No ads or trackers. Students only need a nickname, and projects stay private until shared.
Teachers lead the way
Assignments, automatic grading, quizzes, and circuit races exist so teachers have more time to guide.
Built on open source
Rangkai uses open-source software from the global community, and we list its licenses openly.
Assembled step by step
Rangkai wasn't built all at once. Every feature started from one question: what still makes people stop learning? We designed an answer, tried it ourselves as a student and as a teacher would, and refined it until it felt easy.
Rangkai is designed and tested by our team, and developed with the help of Claude Code, an AI coding assistant from Anthropic. AI helps us write and check code faster; decisions about what to build, for whom, and whether it is ready stay in human hands. We want children to see the same thing: AI is a tool for creating, not a replacement for curiosity.
Rangkai also stands on the work of the global open-source community. The full list is on the open-source licenses page.
- 1
One LED in the browser
The first step: a breadboard, wires, an LED, and an Arduino Uno that really runs programs in the browser, with nothing to install.
- 2
Blocks and levels
So children could join in, we added a block editor and four levels, from Beginner with just blocks to Advanced with multiple code files.
- 3
Mistakes that teach
Circuits are checked as they run. An LED without a resistor appears to burn out, swapped pins are pointed out, and every component has an explanation and pin labels.
- 4
More boards and components
Arduino Nano and Mega, sensors, displays, motors, even a microSD card, so projects can grow with curiosity.
- 5
Lively classes
Class codes, puzzle assignments, automatic grading, live quizzes, circuit races, points, and badges, to help teachers and motivate students.
For our nation
Indonesia will be built by a generation that doesn't just use technology but can create it. We want Rangkai to be one of the steps toward that: the first place a child feels they can make something work with their own hands and mind.
- Within reachHands-on electronics no longer depends on how well-equipped a school lab is.
- Supporting schoolsHelping teachers teach coding, electronics, and AI with ready-to-use tools.
- Raising makersFrom today's first LED come tomorrow's Indonesian engineers, researchers, and tech entrepreneurs.
Let's build together
Rangkai keeps growing. Feedback from students, teachers, and parents means a lot to us in making it better.