I have a new obsession. For a long time I have been addicted to Sudoku. It's a game played on a grid where the player has to fit the digits 1 through 9 in 3x3 cells, 9 cells per grid. You can't repeat any digit in one cell or in a row or column. There is no math involved so the numbers are really just symbols that are easy to remember. There was a time I was playing upto 20 games of sudoku a day! Now *that's* an addiction!
But times change, people change. I've found a new obsession. Kakuro is actually not at all like sudoku except that numbers cannot repeat in blocks. It's a little harder to explain so you really need to play to figure out how the game works. There is math involved in this game, single digit addition only. The top and left of each cell block tells you what the cells must add up to. But really, once you memorise certain blocks of numbers that constantly recur, the game is less about addition and more about physical problem solving, like tetris. For example, in a 2-cell that must add up to 17, the only solution is 8,9. 16 in a 2-cell can only be 7,9, and 7 in a 3-cell can only be some combination of 1,2,4. You see the lower-right corner on this kakuro where 17 going to the right and 16 going down intersect? The point of intersection must be 9 since that is the only number common to both sums. Then the 7 for 16 and the 8 for 17 can also be filled in.
The best online game I've found so far is this one. The only problem with that site is that you get only one game a day - arg! If I find as good a puzzle on a site that doesn't restrict puzzles-per-day, this PhD thesis will never get finished!