Masyu rules

Masyu (also sometimes known as pearls) belongs to the same family as Slitherlink.  They are both puzzles where you must use the clues to draw a single connected loop.  Here are the rules:

1. Use the clues to draw a single, connected loop that does not cross or branch off.
2. Lines must pass through the black circles (or pearls), and must turn at a 90 degree angle within the pearl.  The lines coming out of the pearl on each leg of the angle must continue straight for at least one square.
2. Lines must also pass through the white circles (or pearls), and must go straight through the pearl, but must make a 90 degree turn on at least one of the squares adjacent to the pearl.
3. Not all squares in the grid are required to be filled, but every square with a pearl will have a line through it.

Here's an example: