URL: https://preset-env.cssdb.org/features

Browser / Version: Firefox 66.0
Operating System: Mac OS X 10.14
Tested Another Browser: Yes

Problem type: Design is broken
Description: The code examples are not styled correctly in Firefox. The text is black on a black background rather than having syntax highlighting. It appears the issue is to do with --font-code: "Source Code Pro", monospace, monospace; which is used to style pre elements with font: 400 100%/1.5 var(--font-code);
Steps to Reproduce:
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Firefox:

Chrome:

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