There are four bodies: red, blue, green, and black, placed along a circle.
You can change the positions of the bodies.
You can change the masses of the bodies.
You can change the initial velocities of the bodies. An initial velocity is defined as the x and y components of a distance traveled in one second.
You can change the time increment of the calculations (which changes the resolution of the orbits).
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 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.
In the first four fields from the top are the default values of the masses of the bodies. By way of an example, the mass of the green body is 1.9e30 in the scientific notation.
In the next eight fields are the x and y components of the positions of the bodies. By way of an example, the red value 1.5E11 (meters) in the fifth field, labeled "X0" is the x coordinate of the red body.
In the next eight fields are the values of the x and y components of the initial velocity for each body. By way of an example, the red value -1.0E4 in the fourteenth field, labeled "Vely0", is the y component of the initial velocity of the red body (10000.0 meters/sec in the -y direction).
The field at the bottom, labeled "Increment", is the value in seconds of the time increment used in the calculations.