Friend linked me up to that site last year. I got up to level 16, bookmarked it and haven't gone back since. It sure gets the mind working.
Did you get pass level 10 yet?
There's also another puzzle game at this site to try:
http://www.fasco-csc.com/index_e.php
Basically you're stuck in a room and need to find clues to escape. Sounds easy, no? :P