Change colour of visited link Harlowe 2.0.1

I'm an absolute newbie to Twine, and also CSS in general. I'm cobbling together how to use Stylesheets from guides all over.
Currently, this is what my stylesheet contains:

<code css>
body { background-color: #f5fff0; } tw-passage { color: #17cc5a; } tw-link { color: #0bec5e; } tw-link:visited { color: #08963d; }
</code>

While the text colour of the passage does change according to values entered, and so does the link colour, the
tw-link:visited { color: #08963d; } AND { background-color: #f5fff0; } statements have no effect.

Can anyone tell me what's wrong with the syntax? Or where I'm going wrong and what to do about it?

Apologies if the mistakes happen to be very stupid, I'll do my best not to repeat them