Hmmm. I may be misunderstanding how the test case errors are reported but - having re-read the instructions - it still looks to me that my solution should work. I guess it's difficult to know without being able to see the starting point for test cases that didn't pass?

Impressive. Thanks!

I think your code remains case sensitive... where only "x" and "o" are counted and not "X" and "O".

I used a similar approach, though your code is cleaner than mine. in any case, I am confused by the use of parenthese in "".join([etc.])
Do you understand the syntax and in what instances one would use something other than parenthese?

Hi Alex - perhaps using the following syntax will make a difference?: slice[x:y]