A slightly generalized ellipse

The [color=#0a971e][b]green curve[/b][/color] is the set of all points whose summed distance (distance from [color=#c51414][b]segment L[/b][/color] + distance from [color=#c51414][b]point G[/b][/color]) is 6. Inspired by [url=https://twitter.com/jamestanton/status/559359577385230337]@JamesTanton[/url].

Points [color=#c51414][b]G[/b][/color] and [color=#1551b5][b]P[/b][/color] may be moved around.