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It always made me mega sad to look at the editor in Firefox or IE when using one of the dark themes in the CodePen Editor. WHITE scrollbars =(. And the problem was made worse now that we offer the option to turn off wrapping, you can potentially have scrollbars both directions.
If you were using Blink/WebKit browsers before, you probably won't even notice, because we were styling those already with
::-webkit-scrollbar stuff. But now we've ditched all that and are using this, which means the scrollbars are consistent in all browsers! Yay!