About
There is a world with 1 randomly-placed, randomly-sized, stationary particle. There are buttons to play, step, and reset the model. Stepping the model causes the particle to move. Resetting the model places the particle at a new random location with a new random size. Playing the model causes it to step repeatedly. Resetting the model causes it to stop playing. Once the play button has been clicked, it can't be clicked again until the model is reset.