Note: A general version of this puzzle has been discussed here
There's a 4x4 square, where switches are either red or green. When you flip a switch, all the buttons on that row and column will change color.
Is every starting position possible to complete? If not how many are there that are impossible?
Note: To complete all tiles must be green!
Letting 1s be red and 0s be green, here's an example flip;
1011 0010 1111 0000
1001 0000 0000 0010
The button press for above was the 3rd column, 3rd row.