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Plank puzzles by SwampBeast

This page offers a challenging new selection of plank puzzles generated by a java program called SwampBeast. If you think you have plank puzzles sussed then I recommend you try out some of the 10x10s below and see if you still survive. The rules for the plank puzzles are not repeated here; visit any other plank puzzle page for a reminder (important note... if you haven't tried plank puzzles before, this is not the place to start!). SwampBeast was written by James Stephens of Atlanta, Georgia, USA (www.puzzlebeast.com). To find out more how this puzzle set was developed, read below.

Having never before encountered a plank puzzle I didn't design myself, I have thoroughly enjoyed the opportunity to try solving some over the last few weeks, and indeed still have several of the 10x10s left to conquer. One of my early favourites was Trebuchet, which originally had only 81 moves, but hardly touched the top right corner. I couldn't help putting my designer hat back on and searching for an improvement. It wasn't easy, but eventually I managed to squeeze out an extra 12 moves, creating Trebuchet V2 as now featured.

Title	Size	Planks	Moves	Notes
Staircase	5x5	3	29	Target was to reach 5x5 moves
Six-squared	6x6	3	36	Target was to reach 6x6 moves
Expressway	7x7	3	50	Just go straight across!
Box step	7x7	3	48	A curious layout
Brute 66	7x8	3	66	Named in honour of Route 66
Trebuchet V2	9x9	3	93	Breach the castle wall. See pbs.org for more info on trebuchets.
Shuttle	9x9	3	95	Reminiscent of TCF
Pennsylvania Avenue	10x10	3	95	Making use of primers
Parallel Universe	10x10	4	84	An extraordinary multilayered challenge
Special Delivery	10x10	4	100	Hit the 100!
Junior	8x8	5	75	Introducing P5
Stack of five	9x9	5	109
Conundrum	10x10	5	124
Fort Mudge	10x10	5	121
Revenge of the SwampBeast	10x10	5	174	Only for the bravest few

Solved the lot? Have you name added to the solvers list.

Notes from the Author

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