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Regular pentominoes


  Blokus Puzzler Applet
Blokus is a game devised by Bernard Tavitian, and based on Polyominoes. You have four sets in four colors of all polyominoes in sizes 1-5 (monominoes through pentominoes - 21 pieces totaling 89 squares in each color: 84 pieces and 356 squares altogether). The Blokus Pieces
In the competitive game, each of four players takes one color and tries to place as many of his pieces as he can while blocking the opponents'. In a two player game, each player has two opposite colors.

Placement rules

Each color starts from its own corner.

After the first, each piece of a given color must touch another piece of the same color at a corner, and must not touch another piece of the same color at a side.

Here's what a game might look like if players were being cooperative rather than competitive:
In this example, all the empty space is in two opposite corners.
  Here are some questions to answer:

Following the Blokus placement rules:
  • The 'largest' possible game consists of playing all the pieces of all the sets (356 squares).
    It can be done on significantly smaller boards than the standard playing board of 20x20 (400 squares).

    It can be done on 19x19 (361) or 18x20 (360) boards, which have just 5 or 4 unused squares. In 2007, a 21x17 with just ONE unused square was discovered, as was a 21x16 with NO empty space (but without the four "I" pentominoes).

    In 2008, enlisting computer assistance, I found 13x14, 12x15, and 10x18 solutions for two colors. These have just 4 and 2 empty squares, respectively. The latter two can be duplicated to produce 15x24 (or more 18x20) solutions for four colors, also filling 360 squares.

  • More generally, what is the smallest rectangle that will hold 1,2,3, or 4 colors ?
    For those smaller boards, general solving is very difficult: it seems that there is always a piece or two left at the end which won't fit. (I have found such a solution for 19x19, after many hours of trying.)
    An easier method is to use symmetry: put a mixed, complete set of pieces together (one of each kind), and replicate that configuartion as a quadrant or half of the overall solution. (More information   HERE  )
    (Click the space below to see my best efforts. The image cycles with each click through all results, then back to blank.) Click for results images
  • What is the lowest possible total score ?

    62 + 62 = 124 ?

    This astonishing game was discovered by "Rubik87".
  • Here is the Most Lopsided Game Possible (218-14). Note that red and blue don't even touch.
  • What if you are constrained to play the monominoes (single-square pieces) in the corners of the board ?
  • What configurations can be created, using (2,3,4 colors) with no empty squares ?
  • What is the largest of those ?
  • What other questions might be posed ?
  • Solutions to a Tetrominoes Puzzle