SlideFour is an extension of the sliding puzzle SlideThree which was developed and programmed for Zillions of Games by W. D. Troyka.
 
The numbers 1 to 16 are arranged in reverse order in a square pattern on a 5x5 board. Only a group of four pieces in a row or column can slide. One, two, or three pieces by themselves cannot slide. The object is to rearrange the numbers into numerical order occupying the starting sixteen spaces.
 
The quickest solution discovered so far is 92 moves. But there should be even shorter solutions.
 
 
SlideFour was written for my Diploma Thesis on "Randomized Evaluation Functions in Single Agent Search". You can request a PDF version of the thesis by writing an e-mail to me.