Sigma is the first app enabling users to compete against each other in coding challenges in real-time. In addition, Sigma has a vast collection of programming challenges, starting from complete beginner's level to professional expert's level, which you can practice and solve as you want. Check if a string is a palindrome? Print all the prime numbers between 1 to 100. Given there are two queens on a chessboard, check if they could attack each other. Check if 4 points on the x, y plane form a square. Become fast and clever, plus become a part of the coding community.