When I first started solving algorithm problems from Algospot.com, I had no skills for solving difficult problems. So I sorted problems by acceptance ratio, because I wanted to begin from easy problems. But some difficult problems had high ratios, because only a few master programmers submitted answers for those problems. I wanted to filter out such problems, so I made this. By the way, since I always wanted to build a web app, it was a good chance to start. And I'm writing these useless words to practice English..