Firefox Reader

After intializing reader through onclick="ReaderMode.BrowserOpenReaderMode(event);"

screen #1 of reader in Firefox

Using portions of the aboutReader.css as a userstyle, Light

screen #2 of reader in Firefox

Using portions of the aboutReader.css as a userstyle, Dark

screen #3 of reader in Firefox

The text buttons didn't work but the margin button did.
The Light and Dark buttons worked only after adding the following to the userstyle.