Drag a star into space, then plant planets around it. The green ring is
the habitable zone, where water stays liquid. Throw a body as you let go, or switch to Orbit.
Grab a body to throw it again, or drop it back on the dock to remove it. Pile enough stars
together (8 M☉) and they collapse into a black hole. Drag empty space to pan, scroll or
pinch to zoom.