maybe there's more than one task, but the task i took appeared to be completely specified (the one where you find a balance point - i may have remembered the name wrong - for an array, so that the sum of elements to either side is equal).

it wasn't obvious to me what to do on first read, but when i paid a little more attention, everything was there (including edge cases, as far as i could see). in particular, they gave a formal numerical expression that was unambiguous (and which didn't seem to contradict the text).

Yep, it's good to read the specs in detail ;)

The spec was clear, but the fact that the test dataset used for the test was the very one given as an example wasn't. plus, it was a bit frustrating not being able to fiddle with the test dataset. I would have done it locally with my compiler, but the necessary boilerplate would have lost me time. So, I didn't test enough, and made a silly error which went undetected because of the trailing zero. I still got 75%, but that looks quite miraculous.

EDIT: It appears I can customize my test dataset, and I didn't see it. Silly me.

Yes, it is even possible to add your own data sets, Codility will tell you what you code returns for them. I guess we should make it more apparent in the interface.