Watching course of gamification, I reminded one interesting source — Project Euler.

- Why is this source interesting?

It's just a problemset that contains math and algorithm problems, but they have just one test. Maybe, it's a bit puzzle , so I'll explain on an example:

10001st prime Problem 7 By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th prime is 13.

What is the 10 001st prime number?

Obviously, there is only one answer and one test — and that's all you need to get AC.

This source contains nearly 420 problems

During solving problems,you'll get different achievements, which will motivate you — they have cool design). E.g. they have Fibonacci Fever achievement — for solving 12 problems numbered by Fibonacci numbers.

P.S. First time I met this project two years ago — — I got 20 percent of my mark in one of subjects for solving this problems) I haven't found any posts about this project, so I wrote one.