There is a new game on Kindle: Sudoku ($3.99), by Electronic Arts Inc. I'm looking forward to trying it, but suspect the K2 and even the KDX may be easier to use than the latest K3, due to Amazon's short-sighted removal of the number keys from the keyboard. Sure, they work with the Alt-Key, as they do on the KDX, but there isn't any writing on the keys to remind you how far over you have to go to get to the 5 or 6.
Game Description
Play Sudoku on Kindle - anytime, anywhere.
EA Sudoku contains thousands of built-in puzzles, as well as the ability to enter and play a puzzle from your favorite newspaper or magazine in "Newspaper" mode.
With five difficulty levels from "Easy" to "Insane," Sudoku offers plenty of fun for Sudoku players of all skill levels. Built-in game features let you make "Notes," "Undo" moves, and apply "Error Checking." If you get stuck, you can use the "Hints" feature to fill out a cell for you, or use "AutoFill" to display the notes on all open cells on the game board. You can even track your game stats to see how you progress over time.
EA Sudoku lets you exercise your mind in a fun way.