My Days Are Numbered

I'm addicted to a Japanese logic puzzle. You will be, too.

Sudoku is a logic puzzle. You fill numbers into a grid, using deduction (or, failing that, plain old trial and error). Each row and column must contain the digits 1 through 9, with each digit used only once. The best way to understand is probably to visit Sudoku.com, where there are clear explanations and some sample games. It's incredibly easy to learn.