Ponturo is like Sudoku crossed with NP-complete*
I’m drawn to Ponturo because it’s quick and fresh, and there’s a boardgameish appeal to its archipelago presentation. Also it requires less focused concentration than Sudoku, so it pairs well with television watching.
Play puzzles for free on the Ponturo page of We Love Puzzles. There are also instructions. And the tempting allure of many more Japanese puzzle games.
* = Though Ponturo itself is, I believe, solvable in polynomial time. It just has an NP feel.