Yes, I have met Oskar face-to-face I believe a total of 4 times over the last 4 years at events like International Puzzle Party (IPP) and Gathering for Gardner (G4G). I own a number of his puzzles. I have collaborated with him on a number of his puzzles, Mosaic Block, Real 6x6x6, and Ring Bracelet come to mind. And he and I have both been regular posters in the forums at twistypuzzles.com for years. I've been on there since 2004, Oskar since 2009. Though Oskar has been designing puzzles for decades. I got into designing about 5 years ago.