Lights Out

Click a number in a cell to switch the color of that cell and orthogonally adjacent cells. OFF is blue; ON is yellow.

1	2	3	4	5
6	7	8	9	10
11	12	13	14	15
16	17	18	19	20
21	22	23	24	25

Possible activities

ON: all cells
ON: diagonal line
ON: corners
OFF: only middle cell
checker board pattern

More information Lights out (Wikipedia), tutorial

Other experiments