Q: I found a mistake, where should I report it?
A: There are a few unsolvable¹ problems in the Cho Chikun collection. Some people also believe none of the Hatsuyo-ron problems have a solution, but it hasn't been proven yet.

Q: Why isn't Guan Zi Pu here?
A: Guan Zi Pu contains many duplicate problems. There are different answers involving ko/reductions which should be perused depending on the game situation. As such, I didn't find it suitable to include here. Nevertheless, you may download Guan Zi Pu 1, Guan Zi Pu 2, and Guan Zi Pu 3.

Q: How do I become strong at go?
A: Read uncle Benjamin's guide to become strong. And make sure you follow his advice!

Q: Where did you get the problems?
A: The Cho Chikun encyclopedia, I quite honestly can't tell. The classical problem collections are available over at Uli's. Sensei's library also has an overview of the classical go problem books.

Q: Is it legal publishing problem collections like this?
A: I hope so (I am not publishing solutions, only board positions and most of the authors have been dead for quite a while).

Q: How was the picture at the top created?
A: The old picture was raytraced using POV-Ray. The new picture is hand coded SVG!

Q: But the problems are not interactive!
A: That's not a question! Tasuki hits you with a fan. You heard about Tsumego Hero? If you can get past the eye-bleeding visuals, the user experience is nice. Not on mobile, though!