Sudokulator app for iPhone and iPad

Sudokulator is an easy, fun calculator for Sudoku puzzles. Sudokulator provides 20 puzzle pads that are used to solve Sudoku puzzles. Puzzle pads can be emailed and can be copied and pasted into Notepad (or anywhere else, including Sudokulator).

Sudokulator does not generate Sudoku puzzles. But, it does have one example, with no solution. The puzzle pad in the screenshot is the Example puzzle:
- The button cell in the center is selected
-- The Orange color button indicates the selected button
-- The Blue text indicates a Possibility count of one
-- The Red background indicates only one Possibility
-- The highlighted Number control button (blue) indicates the Possibility number (1)
- The second row contains two cells with the number one
-- The Blue button with the blue background on the left is the Sudoku number one
-- The Gray button with the red background on the right is the Possibility count one

To solve a Sudoku puzzle you must enter the puzzle into Sudokulator
-- Select a Puzzle pad
-- Display the Puzzle pad
-- Clear All the cells in the Puzzle pad
-- Enter each known Sudoku number into its cell
---- Press a Puzzle button to select it
---- Press a Number control button to enter the Sudoku number
-- Use the Puzzle buttons to examine the Possibilities
---- Select Sudoku numbers from the Possibilities and progress toward the solution

Sudokulator has two screens
- The puzzle pad screen which is used to solve puzzles
- The control screen with a few controls for selection, emailing, and so on.

The Control Screen
- Press the Select button on the puzzle pad to display the control screen
-- The Puzzle pad number is the number of the current puzzle pad
-- The Plus or Minus (+|-) button changes the puzzle pad number
-- The Email button will create an email containing the current puzzle pad contents
-- The Copy button copies the current puzzle pad to the pasteboard (as text)
-- The Paste button pastes the contents of the pasteboard into the current puzzle pad
-- The Example button puts the example puzzle into the current puzzle pad
-- The Sudokulate button displays the puzzle pad

The Puzzle Pad
- Press the Sudokulate button on the control screen to display the puzzle pad
-- The Puzzle pad number is the number of the current puzzle pad
-- The Puzzle buttons are the 9 rows of 9 columns of round button cells
-- The Number control buttons are 9 blue buttons in a row for entering Sudoku numbers
-- The Clear buttons are used to clear the whole pad or individual puzzle buttons
----- The Clear All button will clear all Sudoku numbers for the whole pad
----- The Clear Cell button will clear the Sudoku number for the current puzzle button
-- The Select button displays the control screen

Puzzle buttons on the puzzle pad
-- Puzzle buttons have two kinds of numbers
---- A Possibility count is the count of possible Sudoku numbers for the button
-- Possibility counts are blue text
---- A Sudoku number is the number entered into the button
-- Sudoko numbers are black text
-- The background color of a puzzle button is
---- Gray if no Sudoku number has been entered
---- Blue if a Sudoku number has been entered
---- Red if only one number is possible for the cell
-- The foreground color of a puzzle button is
---- Orange if the puzzle button is selected
---- Blue if the puzzle button contains a Sudoku number
---- Brown if the puzzle button is in the same row, column, or group as Orange
---- Gray for all other buttons