| To play this tromino puzzle, click and hold down the 
      mouse key, dragging the yellow square to any desired square cell in the 
      array shown, then release. Then fill in the remaining squares by the same 
      mouse action, dragging the L-shaped tiles, called trominos, so eventually 
      every empty square is covered exactly once by such a tile. Clicking on the 
      Reset button erases the trominos and randomly places the yellow square in 
      the array. Clicking on the Solve button will either complete the puzzle, 
      if that is possible, or result in no progress if you have placed trominos 
      so that no solution is ultimately possible. (Colors may change, but no solution 
      will result.) Once a solution is achieved, clicking on the Recolor button 
      changes the colors of the trominos into just four colors, in such a way 
      that no two trominos sharing an edge have the same color. 
  Clicking on either of the two down arrow buttons at the top, left allows 
      you to specify a new rectangular or square shape for the puzzle, having 
      anywhere from 2 through 32 squares on a side. If you make an m×n 
      rectangle and the product mxn 
      is divisible by 3, no yellow square appears and you should try to fill the 
      spaces with trominos only. If mn leaves remainder 1 upon division by 3, 
      one yellow square appears and you can try to solve the puzzle just as in 
      the original 8×8 case. If mn leaves remainder 2 upon division 
      by 3, two yellow squares appear (these can be relocated if desired) and 
      the goal again is to solve the puzzle by filling the remaining spaces with 
      trominos. This version of the puzzle was programmed
 by Chris Eliot, Visiting Professor
 Computer Science, Amherst College, Spring 2004
 
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