https://www.w3schools.com/css/css_pseudo_elements.asp
Note: As a rule, double colons (::) should be used instead of a single colon (:). This distinguishes pseudo-classes from pseudo-elements. However, since this distinction was not present in older versions of the W3C spec, most browsers support both syntaxes for the original pseudo-elements.

use the fork panel of your solution and run the tests as much as you need

my solution failed on a random test but then I submitted it successfully without any changes

is there a possibility for me to know the test that caused failure?