About the game

Southbound Flock is a free browser game about one of the longest journeys a small bird makes. You fly a barn swallow 6,214 miles south for the winter, from Hudson Bay in Canada to the Pampas of Argentina, in a sky you share with everyone else playing.

How it plays

Flight is a trade between height and speed. Dive and you gather speed; pull up and that speed turns back into height. Every wingbeat gives you a burst of speed, but each one costs energy, and a swallow only has so many. You refuel by snapping up insects on the wing, the same way real swallows feed.

The route crosses eleven real landscapes: the boreal forest around Hudson Bay, the Great Lakes, Ohio farmland, the Appalachian ridges, the Louisiana bayou, a 600-mile open-water crossing of the Gulf of Mexico, the Yucatán jungle, the volcanoes of Central America, the Amazon, the Pantanal wetlands and finally the Pampas. Each one flies differently. Warm farm fields throw up thermals, wind climbing the Appalachians gives free lift along the ridges, volcano plumes lift you hard but burn energy, and storm towers over the Amazon push you toward the trees.

There are no checkpoints. If you hit the ground, the trees or the water, you start again from Hudson Bay.

Controls

Space or click

Flap for a burst of speed. Each flap uses one pip of energy.

↑ W

Pull up: trade speed for height.

↓ S

Dive: trade height for speed.

P M

Pause, and sound on or off.

On a phone

Drag up or down with your left thumb to pitch; tap with your right thumb to flap.

Flying with others

Everyone on the server flies the same route at the same time, and you see other players' swallows with their names above them. Tuck in just behind another bird and its slipstream cuts your drag. Fly into one, or dive onto it from above, and whichever bird hits harder sends the other tumbling, which can end a flight if it happens near the ground. Where a pilot crashes, a feather marks the spot for everyone who flies past later.

The records board tracks the farthest flights, the fastest dives, the highest climbs and the most knockdowns. Speed and altitude records are measured by the server from your actual flight path.

Tips for a long flight

• Flap only when you need to. A long, shallow glide costs nothing.
• Thermals rise under the small puffy clouds. Slow down inside one and it carries you up.
• Over the Gulf there is no land and little food. Climb as high as you can before you leave the coast, and ride the tailwind gusts.
• When a hawk appears, a sudden dive or a sharp climb usually makes it overshoot.

The real migration

Barn swallows that breed across North America spend the winter in Central and South America, and some of them travel as far as Argentina. They feed on flying insects as they go, and they often travel in loose flocks. Many songbirds cross the Gulf of Mexico in a single nonstop flight. The distances and landscapes in the game are based on that route, compressed so a full migration takes about 20 minutes of flying.

How it was made

Southbound Flock was designed and directed by one person. The code, the art and sound (every bird, tree and cloud is drawn by code; there are no image files), and much of the writing were generated with AI, specifically Anthropic's Claude, working from that direction and revised through a lot of play-testing.

The decisions are human ones: following a real migration route, one life with no checkpoints, a shared sky where you can knock rivals out of the air, knockdowns decided by the server so nobody can fake them, ads that never stand between you and a flight, and running the server it all lives on.

If something feels off, or you have an idea, the contact page reaches that person directly.

Cost

The game is free to play. It is supported by advertising shown around the game, never in the middle of a flight and never as a condition of playing.