What is the most complicated 4 piece sliding block puzzle that fits in a 4x5 space?
I think I have a good candidate for that. I found it while writing a Math Games column on Sliding Block Puzzles.
http://www.maa.org/editorial/mathgames/
mathgames_12_13_04.html
If anyone can beat this record... or has anything else on the topic, I would like to hear about it. Ed Pegg Jr