Trying to select text within a codeblock in Chrome (80.0.3987.163, Windows 10) results in some glitchy behaviour. Here is an example from your example GitBook page, below. It is nearly impossible to select single words, single lines or groups of lines, etc.

Native text selection appears to be prevented here because each line of source code has the CSS pointer-events: none set on it. I believe that this property was set in an effort to prevent the underline from appearing when you hover each line of code, since they are marked up as <a> tags. I see two options:

1. Convert the <a> tags to <span> tags and remove the pointer-events: none declaration.
2. Remove the pointer-events: none declaration and instead prevent the underline from appearing on hover by specifying a.sourceLine, a.sourceLine:hover { text-decoration: none; }.

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