[chang1]

I had a similar experience with DuckDuckGo several years ago, but the difference was that I got paid as I progressed through the various stages.

I had to submit a short written design proposal and was told to cap it at a few hours and was paid for it. It was accepted and then I spent time implementing a solution. The pay again was capped at a certain amount of hours, but I ended up going past the recommendation because I was actually having fun trying to figure it out.

I submitted the solution and after a while I got a response with basically, "it was a difficult decision, but sorry we're going to pass" and they wouldn't provide additional detail. It's been over 5 years, but I still wonder why they passed.

I can only assume they had a lot of candidates and they may have had other very strong submissions that were better than mine. However, it took a lot out of me emotionally and affected me for quite some time... more than any other interview in my ~20 year career. I feel for the OP.