Codewars is now one of my favorite sites, because of it’s slick UI that looks like a game, and the way it keeps giving you harder problems to solve. I am using it to sharpen my algorithm skills and practice ES2015, and it has helped me a lot so far in just a few days.
It has Kyu and Dan rank system, borrowed from martial arts or game of Go. I am a fan of Go, and I’ve even written a real-time Go server on Node JS before, so I am already familiar with Kyu and Dan system. Basically, you start from 8kyu, and you go down to 1 kyu as you get better and better. After 1 kyu, you would then become 1 Dan (Master level), and go up all the way up to 9 Dan. The fact that it gives you ranking this way makes you feel like you are training to become a master of coding, and makes it that much more fun.
You can see how others wrote the same code Compared with Hacker Rank, which I used to use, one of the things I loved the most is that you can learn by seeing other people’s code. Once you complete the challenge, you are taken into a screen which shows how everyone else have written the same Kata (Code Challenge). You can see that some people solved it a lot more efficiently with a lot less code, makes you think twice before submitting a problem.
It has “Allies” system, which you can add your friends to your “Guild” like concept. Just like any MMO games, it has allies feature, which you can add friends, see their rank and how they solved problems. I loved how you can form a community there.