A picnic rug, two gaps in the hem, and a column of ants that will take the shortest way between them around whatever you leave lying about. Everything you put down is a wall, so the route is yours: a dotted line shows exactly where they will walk right now and you watch it bend as you put things out. The one rule is that you may never close the rug off, because ants always find a way in, and a placement that would seal it is refused before the tap lands with the ghost turned red. Sauce bottles fire, the cooler chills, the thong lands flat on a whole patch and cannot reach the air at all, and the zapper is the one a blowie actually respects. Blowies fly straight over the lot of it, which is why some of your shrapnel has to reach the air.