Painting black rectangles again

This Nuribou puzzle is large but easy, with the possible exception of its very first step. It is also the blog's first puzzle constructed while I was standing up.
http://pzv.jp/p.html?nuribou/13/13/kek-13zu4k9o6l1zm4l8o-12k4zu6k9k
The Seventh Nuribou

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