About a year ago I logged into a Korean competitive programming website that had really unique problems. They really required a lot of creative thinking — and by creative thinking I don't mean just creative use of mathematics, algorithms and data structures, rather it was about thinking out of the box. The problems were (for the lack of better examples) a bit like CF's April Fools Day Contests' problems. If I remember correctly, it also had some special cases fo some intractable problems as well.

I have since then forgotten it's name and I can find it anywhere. Please help me find that website. Any hint or suggestions towards that website would be greatly appreciated.