
Nonblank blocks are lettered sequentially
according to their order in the puzzle file.
Thus, each move is described by a block ID
followed by the move direction {u,d,l,r}:

test.blk

Solution path with #steps= 100 :


 100  test.blk
a-r  b-d  a-d  b-r  c-r  d-u  d-u  a-l  a-d  d-d  
c-l  d-r  d-r  a-u  a-u  d-u  d-u  a-r  a-r  c-d  
c-d  c-d  a-l  a-l  a-u  a-u  c-u  b-l  b-l  c-u  
b-u  d-d  a-r  a-r  c-u  b-u  d-d  d-d  b-r  b-r  
c-d  a-l  a-l  c-d  a-d  c-d  b-l  b-l  d-u  d-u  
c-r  b-d  a-d  d-u  a-r  a-r  b-u  b-u  a-l  a-l  
b-u  c-l  d-d  b-r  b-r  d-d  d-d  a-r  a-r  c-u  
c-u  c-u  a-l  a-l  a-d  a-d  c-d  b-l  b-l  c-d  
b-d  d-u  d-u  a-r  a-r  c-d  b-d  d-u  b-r  b-r  
c-u  a-l  a-l  c-u  a-u  c-u  b-l  b-l  d-d  a-r  
