Puzzle #18

This is a Heyawake puzzle. 


Difficulty: extreme

Theme: Filled Empty Space

Puzz.link link. 

Recently learned about an advanced Heyawake deduction. Here's my take on it. In addition, this puzzle requires bashing (or some deduction I haven't figured out yet). That's why this puzzle merits an "extreme" rating and not merely a "hard" rating. You have been warned.

Many thanks to rob and Freddie Hand for proving this unique.