Try this website.
http://people.ex.ac.uk/rbd201/riddle/ame.htm
It's fun.
The link's been spreading around for awhile now, and it's popular among a lot of colleges. Your daughters and sons might have already played it or heard about it.
Good luck! It took four of us (college age persons) about 14 consecutive hours (yep, from after dinner to seven in the morning) to successfully pass through all 100 levels.
Careful though. It's addicting. ;P