Hi Steffen.
I think I read somewere that the Solo puzzles were too hard for some. For me the hardest 9×9 are too easy
I think it'll break the API but I would be glad would there be a way to load my "own" sudokus. I once created a wrapper for PocketBook's Sudoku which allowed me to do that. The downside is: Every Sudoku counts as a "book" and thus floods the books database.
I'm thinking about writing a wrapper for SGTPuzzles which would pre-fill the state-file with a Sudoku and then start SGTPuzzles.