Friday puzzles #4

Following its incredible introduction to the world in the finals of the first sudoku world championships in 2006, the toroidal variant gets the pulse of any enthuasiast racing. My effort is in much the same spirit as that original.

The rules are: Fill in each column, row and each region with the numbers 1-9. Some of the regions run off (for example) the top edge of the grid. They continue up from the bottom edge of the grid. Similarly with the left/right edges. The idea is that if you take a nice square, glue left side to right side, and then the top edge – now a circle – to the bottom edge you get a torus – and hence the adjective toroidal. Although if you too are a dabbler in the dark arts of pedantry, you will have noticed that actually a classic sudoku is also “toroidal”. But arguably not as hard. :)

All that is left to be said is this puzzle deserves a slot by itself. Back to two (or more) next week!

    #007 toroidal sudoku – rated hard

All puzzles © Tom Collyer 2009

P.S. The next 2-3 Friday’s might suffer some delays too. I’d say there is approximately a 1/7 chance of the puzzles being published on a Friday, but I’ll nevertheless try to keep to the deadline!