XuanxuanQijingProblem213/Variation 1

White plays and kills. What is the size of the board?  

Denis Feldmann suggests this version. The motivation is to make a geta impossible for White, so White has to drive Black to the opposite edge in a variation that only works on a 19x19 board.
/Solution to variation 1

No other stones on the board ; Black to play and live  

Denis Feldmann : This is the strongest version I could find : after the discovery of the new move at (see Solution to variation 1), the problem becomes an ordinary life or escape one... or is it? (another incredible variation, courtesy of Fan Hui , complicates things ; see below)

No other stones on the board ; Black to play and live  

Denis Feldmann : After some more discussions with strong players (Fan Hui and Noguchi Motoki, among others), and the discovery of a new line (which I may give (or not) in a few days), this seems at last correct, in that Black final escape is only possible by pushing once more on the first line