Hi liam,
I guess you know ‘something’ about css because you got an ‘effect’. However it sounds like you haven’t been ‘specific’ enough with your css – you need to read up on css specificity inheritance.
This is not the place to teach you css – find a basic primer somewhere.
Briefly you need to ensure that you specify any additional css in such a way that it only applies to the bits that you want it to apply to.
The plugin offers a huge number of html tags or ‘hooks’ so that you can be as ‘specific’ as you may need to be depending what it is you want to change.
https://icalevents.com/1596-ical-events-to-dos-etc-styling-with-css-hooks/
‘View source’ or ‘inspect element’ to see the hooks.
At the very least using
‘table.ical’
or
‘div.events_wrap’
before the rest of whatever it is you are tryingto affect, should make the css specific enough to apply to the calendar list only.