## MAKING ‘FULL HOUSE’ PUZZLES

We have to leave behind the squirrel and acorns and oak trees as these are all too slow to draw, so we’ll use grey and white squares and black lines. Here is a puzzle and it’s solution as created with pencil and paper. You will definitely also need an eraser!

Creating a puzzle you have to work backwards. First draw the board (7 x 7 works fine but you can make it larger or smaller). Then shade in some random blocks, perhaps half a dozen to begin with. Now try to draw in straight lines to fill in all the empty squares.

You can see from the puzzle above that lines must stop not only at edges and filled squares but also if they come to a square which already has a line passing through it. This is important because the puzzle is not reversible, that is you can’t start at the finish point and trace the route backwards to the start point. It doesn’t work.

As you go you will find you need to add and take away shaded squares until the whole puzzle works properly. Here is an example where you might shade in squares at A and B. However you now leave square C that you won’t be able to visit. The answer is to rub out square D and shade it in one to the left. This now leaves you problems visiting all the squares in the top right corner of the board.

Changing direction to take in C could leave you trapped in a cul-de-sac at E so again you need a change of direction and more squares shading and unshading. Did I mention an eraser would be needed? The final result is, by chance, a perfect answer because the finish square is right next to the start square.

Lastly here is a page of empty boards that you can print.