cool concept however it seems to be causing ye olde FOUC on firefox so i don't think i'll be using it

this add-on is a great concept and works quite well, i appreciate the ability to set how long a site is whitelisted!
however, i kinda wish it had the option to set your own "valid reasons"? as an example: sometimes i want to visit a blocked site for a specific post with a tutorial in it, and it's kind of inconvenient to either have to lie or turn off the extension and reload the page. i realize this could be abused if you could type whatever you want (i.e. set your valid reason to "a" so you only have to type one letter to get in and not think) so maybe there could be a minimum character limit to circumvent that? just an idea.
it would also be useful to have a link whitelist, so that you could exempt specific pages on a site from the blocker while still blocking most of the site -- blocking twitter.com blocks everything on twitter and blocking twitter.com/blocks home blocks nothing on twitter... what if i just want to block my main timeline and not the post containing something i need to look at? maybe twitter is especially picky about this sort of thing idk though.
anyways thank you for making this! hope this feedback is reasonable, sorry it's so longwinded, i've never written a review for an extension before