In a parallel universe far away, Newton's constant of universal gravitation is equal to 1. Three equal masses (weighing 1 kg each) are placed in space a couple of meters part, given an initial velocity, and let go. What do they do? See for yourself.
Full documentation is available here.
The x in the left pane is the mathematical origin; the x is the center of mass of the system.
Click "Start/Stop Animation" to run the simulation. When animation is stopped, click and drag planets or the tips of their velocity vectors to change their initial position or velocity. Click and drag the shape sphere to view from different angles.