Up front: I solved the challenge, so this isn't a request for hints or help on the solution. Admittedly, this took well over a week, a lot of reading and ultimately just a lot of random guesstimation. When I got the answer, I was surprised to see the "congrats you've got the first part" message.
Would someone be willing to walk me through why this works? I was trying much more complex inputs, and the fact that it ended up being so simplistic surprised me. What would this specific input have driven in terms of a response that would have been desirable?