If you thought Sudoku was the greatest number puzzle game in the World then you obviously haven't tried Kakuro.
Mastersoft Kakuro lets you play this mathematical version of crosswords on your Pocket PC. A Kakuro consists of a game board made up of filled and empty cells. Some cells contain a diagonal slash with one or 'clue' numbers in them. A number in the top right corner is a clue for the 'across' sum, and a number in the bottom left corner is a clue for the 'down' sum. The object is to insert digits between 1 and 9 into the empty cells so that the sum of the empty cells equals the numbers in the clues associated with them. No digit may be used more than once in each sum.
Mastersoft Kakuro is a comprehensive version of the puzzler, offering unlimited Kakuros over six difficulty levels. It's rammed full of features, including a unique number entry system with the ability to show your workings out, and various types of hints to aid your play. There are all manner of statistics available in Mastersoft Kakuro, which allows you to track your progress from beginner to Kakuro master.
The playing area in Mastersoft Kakuro is completely skinable, allowing you to change the background, number colors, and number styles. You can also choose to enable or disable sound effects.
One thing I think could be improved in Mastersoft Kakuro is its help system. There is an online help page but I thought the game would've benefited from an interactive tutorial to help beginners.
That said, Mastersoft Kakuro remains the best way to enjoy this taxing Japanese number puzzle on your PDA.