Click anywhere within the grey area to add a solar mass. You can additionally toggle the other inner planets of the Solar System. There is a counter on the upper left corner of the simulation. On the upper right corner there are instructions for special places in time and space where if you click at the right place at the right time strange stuff will happen. Often after you chose one of those special places you will have to refresh the page to choose a different one.
Okay so basically there is an alien species attempting to exterminate us. They visited us a few days ago and did not like us very much, we're gonna call them the evil-doers. These evil-doers can create what we call a Mass Bomb. It is a special device that does the reverse of a nuclear bomb, it converts energy into mass. Through some quantum information device, with enough energy they can teleport an entire solar mass from another point in the universe right to where the bomb is. This can create catostrophic effects for us humans. For instance if the first case scenario is played out (labeled 1 in the sim) the mass bomb adds mass to the sun, this causes to Moon's orbit to destabalize and collide with the Earth (not good). Or if the bomb goes off at the second (1) scenario then the Moon can maintain its orbit, this is a best case scenario for us. The other two scenario's have the Earth and Moon system either decoupled (2) or the Earth flung into interstellar space (3). Clearly these evil-doers should be taken seriously.
If you spam the Venus and Mars button you can create a large amount of orbiting bodies. If you get say, 20 of each planet and then click on the sun (adding a solar mass to the sun). Then the system contracts and within the next 4 mintures you can watch the Solar System organize to a few planets with circular orbits.