If you understand this pattern it's a good idea to eleminate the lights, and get the on-lights close together.
Also get them to the border, because negations will not take place outside the frame. :)

This riddle isn't hard, if you understand how it works. :)
The position you press on, will negate all the lights in a cross patern.
010
111
010
If you press on the 1 in the middle, all will be 0. Negate means it will make an off-light on, and on-light off.

100
011
111
If we press on the 1 in the middle (2,2) we'll get:
110
100
101

We negated all the lights in the cross pattern.