This is a nice game. It is not too hard and not too easy, either. I hope you keep the good work.
BTW, the answer to the diagonal thing reminds me of big games released with lots of bugs due to lack of time to fix them.
Anyway, I found a bug (not the diagonal thing, of course). On lvl 28, if you clear the white balls first and then the blue ones, one of the silver balls falls over one of the green balls making it impossible to finish the level. I will keep playing in case I find another bug (besides the diagonal thing).