I bumped into lejos in a section on Mindstorms toolchain options for Macintosh in one of my dad's MacWorld magazines. BrickOS for C and C++, lejos for Java, NQC, etc.

After the RCX was reverse engineered, all sorts of language support appeared. The 'hacker' community around Mindstorms was huge in the 00's. My favorite thing in the world was the Exploration Mars expansion. When I was around your son's age, my parents introduced me to computers by getting me a LEGO Mindstorms Robotics Invention System 2.0 set for Christmas in 2001. I think you have to try with different things to see what will capture your child's imagination. Raspberry-pi with Raspbian, Arduino, Robotics kits, etc.) although nothing that he showed major interest at the time.

This project does require a lot of my own time. He is able to follow along with the videos and understand the material at a good level. We are currently building Ben Eater's 8-bit computer (/8bit) and he absolutely loves it. He used this series of YouTube videos to learn about Godot. He showed strong interest, built a few games in it and even understood enough of the Python like language that Godot has.

I introduced him to Godot when he was 9. I bought him some cheap hardware (Meowbit) to put his programs on and he loves showing off his games to his friends and everyone else. He got absolutely hooked and it is still his favorite platform today. I introduced him to MakeCode () around 8. I tried to introduce him to Python (around 7.5) by following an online book about game programming. (Unfortunately I do not think they make this kit anymore.) Verdict: MINOR SUCCESS. It came with educational software that introduced him to programming languages, etc. The kit retailed for about $250 at the time and a kid could assemble it 'like LEGO'. I bought him a Kano computer kit when he was about 7. While I never found the perfect machine here is how I have been introducing my now 10 year old son to the world of computers:

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