Sudoku

Sudoku has three simple rules. The numbers 1 through 9 may only appear once in each row, column, or 3x3 block on the puzzle board. Some numbers are already filled in. Your task is to fill in the rest. Sudoku has been around for decades. The techniques for both generating and solving these puzzles are well researched and there are many apps and solvers out there for your enjoyment. So why another one? This is my first Android app so I wanted something simple that didn't require a lot of effort to create. Was I ever wrong. Beyond generating puzzles with a guaranteed single solution, puzzles should be made intentionally easy or difficult and that is where the rabbit hole opens. The first step to creating a good puzzle is to solve it and the techniques required to reach the solution determine the difficulty. There are about a dozen base techniques ranging from fairly obvious to complex and time-consuming to work through. This app implements the first seven and can already produce some maddening puzzles. Easy puzzles can be solved without a tremendous amount of effort as they should. Medium and Hard puzzles ratchet up the difficulty and I have not yet completed an Expert puzzle without guessing. Guessing is not one of the implemented techniques! The app also allows you to generate puzzle booklets that can be printed and handed out to your friends and co-workers. Each printed puzzle has a QR code that will allow the same puzzle to be opened in the app where you can check the solution or solve it yourself. You can print single puzzles, two puzzles side-by-side, or four puzzles on a single sheet that can be folded into quarters to create a booklet. You can take the game with you even when electronics aren't available. Have fun and drill your brain!