Please email support@mindmagik.com if you cannot find an answer to your question.
Reporting a bug or providing feedback can be done in one of two ways:
1) Inside the game, go to the PLUS menu (small icon with an + on the main menu) and select EMAIL SUPPORT. The local email client should be automatically launched with the TO: SUBJECT: and BODY: auto-populated and ready to edit and send.
2) Go to the contact page of this website and send an email to support@mindmagik.com
This is most likely because the local email client has not been configured to send email on the device itself. Check that your device can successfully send an email outside of the Sudoku app.
To add a pencil note, tap any empty cell to zoom in. When zoomed in you can add notes to all of the cells within the same block at the same time. Pinch out to zoom out, or touch any object on the screen other than a pencil note.
Beginner, Easy, Medium and Hard do not require any special type of solving techniques. The level is based on the number of starting numbers given in the puzzle.
Expert will require most players to use pencil notes. Note pair techniques are needed, such as pointing and claiming pairs.
Crazy level introduces naked and hidden pairs.
Fiendish and Insane have X wings and other more advanced techniques that make the puzzles very challenging. Diabolical puzzles are very difficulty and although very advanced players can solve these using advanced chaining techniques, most players will require some guesswork to solve these.
The extreme black puzzles are only possible when entering a custom puzzle. These are even more difficult than Diabolical. Even though they are valid puzzles, these are often referred to as "Impossible" puzzles. They will almost certainly require a human player to guess. The algorithm used by the application to solve these is so intensive that it is not possible for a human to perform in a timely manner. As such, the out-of-the-box puzzles do not include extreme puzzles.