Welcome to kakuro, the addictive brain teaser! This Japanese puzzle craze, sometimes called "cross-sums" or "kakro," is sudoku's bigger (and tougher) brother. As with all good puzzles, the rules are easy to learn but the game is difficult to master. These 101 puzzles are specifically designed to introduce novices to the game. Like a crossword puzzle, the playing area consists of filled and empty squares. Some of the black squares contain a diagonal slash from top left to bottom right, with numbers in them--the clues. A number in the top right corner relates to an "across" clue, and one in the bottom left to a "down" clue. The object is to insert digits from 1 to 9 into the white squares that add up to the associated clue; however, no digit can be duplicated in an entry. For example, for a total of 6, you could have 1 and 5 or 2 and 4, but not 3 and 3. Easy, right? Beware! It gets more complicated. In case you're stumped, solutions appear at the end.