At A Cleverly-Titled Logic Puzzle Blog you can find a lot of Pearls Of Wishdom Puzzles (a.k.a as Masyu) which looks a bit like Slitherlink puzzles.
The rules are simple:
1. Draw a single loop that connects the grid cells. The loop may only travel horizontally or vertically, and never diagonally (so all turns are of 90 degrees). The loop may only turn at the centers of grid cells. The loop may not cross itself or branch off; in other words, the interior of the loop will be a single polygon.
2. The loop must pass through every pearl (circle) on the grid.
3. The loop MAY NOT turn at a white pearl, but MUST turn at ONE or BOTH of the adjacent cells in the loop.
4. The loop MUST turn at a black pearl, but MAY NOT turn at EITHER of the adjacent cells in the loop.
Tags: Logic Puzzle