Rules :

1. Any live cell with fewer than two live neighbours dies, as if by loneliness.

2. Any live cell with more than three live neighbours dies, as if by overcrowding.

3. Any live cell with two or three live neighbours lives, unchanged, to the next generation.

4. Any dead cell with exactly three live neighbours comes to life.

The Game of Life is a cellular automaton devised by the British mathematician John Horton Conway in 1970. It is the best-known example of a cellular automaton.  More info via Wiki

Instructions :

Click on a dead cell to give life to it, click on an alive cell to kill it.
Drag over dead cells to give them life, drag over alive cells to kill them.

Click on Step to go one generation further, Start to go on in automatic, Stop to pause, Clear to kill all the cells, Random to give life to random cells.