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Throw a note from a high window at dusk and fly it across the rooftops to the one sill that is lit.

The throw sets the whole budget. After that you trade speed for height and height for speed, ride the warm air off the vents, and keep the note away from the crows with a tight turn or a foil strip they want more.

Five windows, three notes, and a sky that darkens with every delivery. When you can fly it by hand, teach a script to do it: the same flight, one decision every tenth of a second, with sensors that reach only as far as the plane can see.