Conway's game of life is a cellular automaton. The simulation can be started it from a random setup or the pattern can be given by toggling cells on or off by clicking on them.
More information about this simulation on the wikipedia page Conway's Game of Life.
With the left mouse button pressed you can drag an area to manipulate. Use the keyboard to: <c>: copy, <x>: cut and <v>: paste. Manipulate the copied content with <m> to mirror and <r> to rotate. And the selected area can be cleared by pressing <0> or filled by pressing <1>.