I had made changes to file
usr/share/gnome-shell/theme/gnome-classic.css
And
usr/share/gnome-shell/theme/Yaru/gnome-shell-theme.gresource
to decrease space between icons in app list. But, my system is now broken and after restart, I can't boot into Ubuntu.
I can go to recovery mode and access my terminal and grub is available too. I am using 20.04. How do I reverse those changes and properly boot into Ubuntu.
You have to reinstall the packages which provide these files - backup and reinstall:
Backup:
Reinstall:
Then reboot.