Because more beginners vote codes than experts

Same here! I didn't know where to start, but someone answered another comment with this link: https://medium.com/javascript-scene/composing-software-an-introduction-27b72500d6ea
This kata is challenging, but becomes simple once you apply this idea.

Spoiler flag?

Thanks, and well done that you solved this one! The difference between 4x4 and 6x6 is that 4x4 can be solved by just brute force. For 6x6 you need to apply at least some rules first to limit the number of solutions because you do not get enough processor time to perform a brute force. In my own experience: for my first solutions I needed tons of code, but when I tried again in js I found a solving strategy which made it all of a sudden a little more easy than a 1 kyu... :)