I should write something in English too due to AdSense Ads in English instead of Polish :)
So there is this game at http://www.supuzzle.com/. I tried to solve this „easy” for the first look puzzle and give up. But it was so addictive that I have to google for help. Then I googled that in two dimension world is impossible to solve it! There is even mathematical prove of it – here. However in this case there is a glitch that helps to solve puzzle.