Orbholt

Orbholt is a gravity sandbox. Drag back from any point and let go to fling a moon; a dotted line shows the path it will take around every star and planet on the field. In free play, place up to eight stars and planets, erase them, speed time up and watch the trails draw orbits, slingshots and crashes. Eight challenges ask for real orbital feats: two full laps around a star, parking a moon in a ring, collecting sparks in one flight, orbiting a planet instead of its star, slingshotting out through a gate, keeping three moons up at once, a loop around two stars and a final puzzle where you may place a planet of your own. It plays in the browser with a mouse, touch or keyboard.