think....
think...
think some more....
walk away....
think some more...
gets it....

LOL

::tips-hat::

nice use of destructing in that for loop!

It's not how CodeWars problems work.

Each problem is created with some difficulty level in mind, and in this case it's rated as 4 kyu in 8 to 1 scale. So it is actually how author created it, and how they meant it to be challenging. If you choose to go for a blue, 4 kyu kata, you should already know what difficulty to expect. Hint: blue is where easy one-liners end and some research is needed, usually.

It's also quite unprobable that you will find an easier version, because it would probably be considered a duplicate - but sometimes it happens that some problem has easier and more difficult version. Not that often tho. You can create the version with "low-ish" level of difficulty if you like, and see if community approves it.

If you're using the trainer (the one in the main page) you should set it to "fundamentals" instead of "rank up" to get the elemantary katas. Though usually it's better to search for katas from the kata list: the second button in the left bar. You get to search, filter, order and choose any katas you want there.

Good point.

New to the site. Not sure how fast they ramped up.
In addition the site chose the problem for me, not the other way around.

What the heck are the dan problems like?!?

Why are you doing a 4kyu kata if you're brushing up skills on a new language?

Go do some white katas. This is not the kata for you.

I am here to brush up skills on a new language, not advanced CS techniques.

A "naive" implementation can pass all but one test case which requires a more performant solution.

Please split this into two problems: one "low-ish" level and one "high-ish" level.
"My daughter was very happy with our program. After she got her homework done she played with it a bit. 'Daddy, why does '12345' take so long to run?

Also, consider bumping the low-ish one up just a bit. Even that has a mix of tail and non-tail recursion.