It's funny. When you're at school, you barely register grids and numbers. You have a dim notion that they're somehow involved in mathematics, possibly geography, but they're approximately as relevant to you as long division, the water table, and the word 'conjugate'.
Then, a few years later, somebody leaves a sudoku puzzle half-finished on a train, you take a look, trace your finger along the lines, a little bell rings, and suddenly you can't get enough.
Crosspix – a game popularised by Picross on the DS and entitled Tsunami in its paper form – is what mathematics should have been like at school, and a more accessible answer to sudoku.
For those who don't know, it works like this: You have a blank grid of, say, 10x10 squares. As in Minesweeper, the squares either conceal something or they don't, and it's your task to work out which are which using the numbers the game sparingly supplies.
Whereas Minesweeper places these numbers within the board, however, Crosspix lines them up outside it, above and to the left of each column and row, so that if 4, 6, 2 is provided beside a row there will be a line of four, then six, then two filled squares, in that order, each separated by at least one unfilled square.
If the grid is ten across and the number given is 10, easy. You just fill in every square in that line. If the 10 fills a row, then you know where at least one of the squares in each of the perpendicular columns that make it up belongs, and from those you can usually deduce the locations of a few more filled squares. And so on until you've got yourself a picture.
