Or the more free TIC-80. I have paid for both, but never used either enough to be able to say one or the other has any significant advantages.

https://tic80.com/

This and TIC-80 recommended bellow really feel more like a fun challenge for a programmer than a creative tool for a kid. Was it the first time your kid was exposed to any kind of programming?

True, was not the first exposure, and I still did a good lot of hand holding at the beginning.