Use "ZOOM" options in your internet browser if you can't see the whole applet (top of y-axes to the bottom) on one screen.
Click on the "PLAY" button , BOTTOM LEFT, to start the animation and click again in the same place to "PAUSE" the animation.
At anytime you can use your mouse to click on the slider button and drag the years to whatever number (0 to 20years) you wish.
You can also use the ARROW KEYS (up & down), once you have clicked on the slider button, to move the slider in precise, one year steps.
Internet Explorer users you may need to click on "Show All Content" before you can view the applets below.