Friday Puzzles #20

Carrying on from last week, here’s another topologically themed sudoku. This week, it’s the turn of the projective plane. You’ll also have noticed that this week, in a noble and glorious gesture to save the planet, I have removed the colouring of the 9-cell marked regions. Indeed, dear reader, I have potentially saved some of your precious, precious, colour printer ink.

Now, this will make things difficult for those who can’t visualise the surface via the given identification space – and so the puzzle isn’t as hard as it might have been. I might revisit this design in coming weeks to really exploit some of the beautiful logic induced by this particular grid structure.

    #024 Real Projective Plane Sudoku – rated medium

All puzzles © Tom Collyer 2009.