I created this Scratch proof-of-concept for 3D pong (https://scratch.mit.edu/projects/1881311/ https://scratch.mit.edu/projects/1881311/) over a decade ago when

I created this Scratch proof-of-concept for 3D pong (https://scratch.mit.edu/projects/1881311/ https://scratch.mit.edu/projects/1881311/) over a decade ago when I used to teach kids. I also found several other examples on the Scratch website which show how to build 3D graphics on a 2D canvas. After many years of teaching kids to code, I would say the best introduction for a 9 year old is to start with block-based environments to build structural thinking fundamentals, before introducing him to typed programming languages. The issue I see in starting in Unity or an equivalent high-level abstraction (e.g. threejs.org), is that it doesn't build strong fundamentals in how you think about solving problems. Many kids these days think they are "coding" when they are really just modifying a collection of examples and starting points (which has fueled the burgeoning industry of summer camps teaching "Minecraft modding"). As is the case for many other skills, great amateurs make great professionals.