"hidden singles" (groups in which a value is possible in only one cell), pairs, and so forth. And the practice mode helps you learn solving strategies by generating puzzles that exercise the specific strategy you want to learn. If you get stuck, SudoKoach can give you three levels of hints. A little hint tells you what to look for (e.g. naked single, hidden single, box/line elimination, etc.), but doesn't give any details on the value or where to look. A medium hint tells you what to look for and what value is involved (e.g. a hidden single with the value 7). And a big hint shows you exactly where the next move is, and explains the logic behind the move. These explanations help you learn the more advanced Sudoku solving strategies, so you can become a better player. Why not download SudoKoach and try it out? It is a lot more fun to use than it is to read about!