Very neat, playground was much more put together than I expected. A bit of aliasing but otherwise very clean (for some simple twiddling at least).
The default layout seems to have the classic "horizontal scrollbar because it doesn't account for a vertical scrollbar when setting the width" design flaw. Not sure if that's specific to the example or a "just how the sizing system works" thing.
When you mention the scroll bar are you talking about in the preview or the editor? There shouldn't be a horizontal scroll bar anywhere, so we should fix that. Also, what browser are you using?
Preview, the issue will go away if I force enable chrome://flags/#overlay-scrollbars. Screenshot (w/ flag set to default): https://i.imgur.com/tExERgS.png
Google Chrome 128.0.6613.120 (Official Build) (64-bit) (cohort: Stable)
Windows 11 Version 23H2 (Build 22631.4112)
Issue does not occur in Firefox on the same system since it seems to default to overlay scrollbars.
The default layout seems to have the classic "horizontal scrollbar because it doesn't account for a vertical scrollbar when setting the width" design flaw. Not sure if that's specific to the example or a "just how the sizing system works" thing.