Crosses

Make the horizontal and vertical sums equal

Swap pairs of tiles by dragging until the arrangement of numbers is such that the vertical
and horizontal numbers sum to the same value.

Start with 5 tiles and then use the Set size buttons at the bottom to try 9. If you're feeling confident, give 7 tiles a go—but be warned, it's a little trickier. Maybe you can work out why?

Set size:

- Is there a special tile position?
- If you find one solution, can you make it into a different one by swapping in the same row?
- How about by swapping between horizontal and vertical?
- Will this need more than one swap?
- How should you choose which tiles to switch?
- What is the minimum number of moves to solve the puzzle and what does it depend on?
- How many solutions do you think there are all together?
- Can you make a version of this game using a different number of tiles?
- Can you make a version of this game using a different arrangement of tiles?