Runway

you are the tower. land them all, and keep them apart.

air traffic control: draw a path from each plane to the runway of its colour, and keep them from touching

Every plane flies the line you draw at its own speed and lands when the line ends on its own runway. Two lines may cross; two planes may not be there at once. A plane with no line flies straight and bounces off the edges.

Concepts: air-traffic, collisions, planning.

An interactive you play with one thumb, on Wundr.