If you look closely, you can see that in addition to what you typed above, you can also see the output
puts write the String “Hello World” to the console,
and returns nil
So, it does what it needs to do. It does not create anything to the model.
If you want to Draw Something, look e.g. here
(https://developer.sketchup.com/article-writing-your-first-code)
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Other places you can start:
https://forums.sketchup.com/t/ruby-learning-resources-wikilists