Orbit Sandbox: an n-body gravity simulation. Drag from empty space to launch a body; a dotted line predicts its path. Bodies attract each other and merge when they touch. Keys: 1 to 5 load presets, Q W E pick the launch mass, space pauses, [ and ] change the time warp, Tab on the canvas selects bodies, Delete removes the selected one, F follows it, T toggles trails, S shares, C clears.