This one took me really long to see, for some reason. I had the right idea on the left side, but not so on the right. Finally got it though. Some interesting logic here, but feels maybe a bit messy.
(12 years ago) I didn't find this easy. :) 10 tries.
*****
EDIT 2022, 18th Nov. - Still not easy. But I got lucky to solve it fast. Giving 5 stars, today. :)