Click or touch squares to toggle them between alive and dead. Use the play / pause button to pause and unpause the game, and the slider to adjust the speed. The game autopauses when the mouse is over the board.
As you can see below, this version is pretty snappy even with a large number of squares
This is the SVG version of the game, before I rewrote it using canvas for performance reasons. SVG is a great format, but not suited to applications with a very large number of elements. Mouse over the grid and click squares to toggle. Mouse out to start the game. Mouse back over to pause and toggle squares.