Press the left/right arrows to make it move, or down arrow to make it stop. When the train is offscreen, the thought bubble tells how far. Bigger train and more carts. It's fun to hold down the left arrow until the train's bubble thing says 10,000, then let it slow down. By the time it stops, it is at about 20,000 Then hold down the right arrow until it comes zooming back - it gets going pretty fast.
