In the prior versions of the widget this didn't happen, so I assume it's a bug. (I'm using an older version on my website in fact)
Actually, in the older version canvas had also 100% on both, but it also automatically updated itself with the correct proportions, looking in the inspector.
by the way I like the idea of placing inline canvas and json!

Also, if I can make a tiny request, I'd love to have a version of the script where after the animation on click is done goes back to the animation set in the beginning. buuut I can also ask friends for help on this >.>
I had in mind I wanted to make an animation where the character waves at you or does things if you click on it, or that does other stuff, like saying thank you, if you click e.g. on a download button. But that's a plus. If this distortion thing would be solved it'd be better >.<
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Old version: (no bug)


New version: (with bug)


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Also I confirm that if I replace spine-widget.js with the old one, it works well again.