It's a little interactive Conway's Game of Life simulator.
Click on cells to mark them as "alive" or "dead". Run and stop a simulation using play / pause buttons. "Zoom" in or out using plus and minus buttons. Clear the state using "Undo" button.
Go ahead, make a glider, play with diff patterns it's quite entertaining.
It's written in Elm and intended as an excercise in Elm. The implementation is quite naive, so criticism and PRs are very welcome.