Moeboid, I have been on the site twice now and I think I solved only 4 problems so far. But caution is demanded here: If you start to dig into this stuff, you easily get addicted and totally lost So, maybe I should limit it to one visit per week and solve one or two problems?
Most of the problems can (easily) be solved with programming, but that's taking away the fun of it a bit. For somebody that likes puzzling and that studied maths a long time ago without using it in daily work anymore, it is quite a nice site.
the reason i'm doing these is to learn how to write programs, so i've written programs for all of them even if i could have solved them without it. the 5 that haven't been completed yet are because i don't know how to import data. working on it, though. i'm really hoping that soon i'll be able to write useful programs.