Notes from the Author (2002)

SwampBeast is a Java application which consists of two basic modules, a puzzle generator and a puzzle mutator. The puzzle generator creates a large number of random puzzles, and attempts to solve each one. If a puzzle can be solved, it is assigned a score which reflects (at least in theory) the difficulty of the puzzle.

The puzzle mutator takes the best puzzle from the generator and applies a variety of mutations such as moving planks, adding, deleting or moving stumps, etc. Higher scoring mutations are retained in place of the original puzzle. A typical puzzle on this page is the result of perhaps 100,000 generation steps followed by 10,000 or more mutation steps.

The scoring algorithm continues to evolve from the first versions of SwampBeast. In the early days the scoring criteria were chosen to produce puzzles with long solutions, and as a result many of the puzzles had a large number of "flip-flop" moves, i.e. sequential moves using the same plank. The criteria were subsequently adjusted to explicitly discount flip-flop moves by shorter planks, and as expected the resulting puzzles proved to be harder to solve. The current criteria also give a higher score to solutions that make frequent changes in the set of active planks.

Another twist on SwampBeast puzzles is the use of priming patterns. Rather than starting with a totally random puzzle, the grid is primed with a pattern designed to maximise the use of the longer planks. Pennsylvania Avenue, Special Delivery, and Parallel Universe were produced using priming patterns with diagonal corridors through the puzzle. These patterns were distorted somewhat in the mutation process. (although, surprisingly, the pattern remained completely intact through the mutation steps for Parallel Universe.)

Jimmy Stephens - Feb 2002
www.puzzlebeast.com