There are eight bodies: red, blue, green, magenta, cyan, yellow, gray, and orange, orbiting along a circle.
There are three control buttons in the top of the left column: Play, Pause, and Reset, followed by a number of editable fields below. Click on Play button to run the simulation. Click on Pause to stop it. Click on Reset to restore the defaults.
The fields show the default values of the masses that can be changed. All values are in the metric system. The colors of the values respectively correspond to the colors of the bodies. When you hover the mouse cursor over the field, it displays its identifying label. The default masses of all bodies are 3.2e29.
The field at the bottom, labeled "Increment", is the value in seconds of the time increment used in the calculations.