Join the dots in a bid to create squares on the grid.
Colour the squares by completing a square, and the winner is then the player who's managed to fill the most squares.
You'll need to lightly swipe to select playing positions. It can be a little bit fiddly on tiny screens, though.
I think I need to learn how to do gestures properly!!
What I Didn't Do
The two player mode ended up being really awkward, with players often taking each other's turns. The "Whose turn it is" needs rejigged, I think.
So, until I've figured that out, you'll just have to resort to actual pen and paper for two player mode
Since this game is traditionally played on Pen and Paper, I've often considered making some kind of Foldapuz edition, but can't quite figure out how to turn it into a quick puzzle.
If you've any thoughts on that, post 'em in the comments!