Slitherlink

If you think that slitherlinks are NEW puzzles, then you are wrong.
On http://www.oct.zaq.ne.jp/woodside/slithe/ you find puzzles from 1999 !!!

You have to draw lines between the dots to create a continuous loop.
The numbers tell you how many lines that square has.
You find an tutorial on http://www.kwontomloop.com/tutorial.php

On http://www.oct.zaq.ne.jp/woodside/onlyone/ you also find hitori from 1999