I'm also stuck (with +1 characters) and can't seem to figure it out ;-)

glad to hear that

I personally liked this question a lot! I was having trouble solving this question (with a then best of 36 chars) when I realized the intuition behind how this question was supposed to be solved!

Definitely my favorite problem so far. :D

now it works tnx

I've tried it myself, and they aren't the same to me. When I say Reset, I mean the button below CW code editor, not just refreshing the browser

Please verify if that works or not.

sample test cases are same

sample test cases are same

Should be fixed. Try copying your code and hitting Reset button.

File "/workspace/default/tests.py", line 15
test.assert_equals(count_black_cells(6666, 8888), 177
^
SyntaxError: '(' was never closed

Add random tests. Thank for you reviews

"Random tests" are not random.

https://docs.codewars.com/authoring/guidelines/submission-tests#random-tests

good kata, but random tests needed.

amazing kata, the first one i had to forefeit. the concept illustrated is brilliant.

It's okay, don't give up and you'll succeed.