Hi there.

I just tried reproducing all the steps in the tutorials, then adding the onTrigger for the button, exactly as you wrote in your mail, and it works for me.

I don't get any errors in the console. I implemented it in a clean installation of Pharo with the latest release of Willow-Playground, on Windows 10, rendering with Opera.

Could you check if those same steps give you the result you mention?

Thanks for your interest in Willow!