Initial phone screen, then a deeper phone call with the CEO. Finally they gave you a take-home assignment to complete at your leisure. This seemed very forward-thinking/progressive of them, and much appreciated. The task was not very challenging (not algorithmic), with a little parallelism requirement to challenge you a little. This had to be implemented on their platform, which seemed pretty awkward and even flaky at times. I'm quite comfortable with this kind of code, and took a long time to polish the solution to very high standards. Some trivial initial changes were requested, no problem. After that, the only feedback I received was "*** person tried it again, it still doesn't work". To get such a terse response after providing such a polished and (in all honesty) well-prepared solution seemed like a surprisingly rude way to treat someone who has invested so much time. A thorough going-over of their requirements showed no missed requirements. Perhaps it was an ambiguity. I would caution others against wasting their time with this. 5 weeks from initial contact to final word is also far too long.