ZenKen81 is Sudoku with a mathematical twist, the classic KenKen puzzle invented by Tetsuya Miyamoto. Every puzzle is a new puzzle, no repeats, and no subscription to buy new ones. Puzzle sizes range from 4x4 to 9x9, for the beginner to the expert. Build your own puzzle. Choose your own level of difficulty.

We've created a sleek modern interface designed to take advantage of the iPhone's unique touch screen capabilities. It's an interface that is designed to let you immerse yourself in the puzzle and let you play as fast as you can think. There's no need to switch back and forth between modes or squint at hints. Just play.

Use your imagination to create puzzles, not just to play them. We've given you the tools to create your own puzzles at the level of difficulty you want. Want easy games? Select small puzzles and choose two cell cages. Make things harder by increasing the size of the puzzle and adding in four and five cell cages. Or you can hide the arithmetic operations in the clues and really give yourself a hard time.