How to play
You fly a small cargo drone across a city at dusk. In every level an orange parcel waits on the street or on a roof, and a green pad marks where it has to go. Fly over the parcel and let the hook on the rope touch the box: the hook catches it. Then carry the parcel round the buildings, cranes and moving obstacles and lower it onto the pad. It must touch the pad no faster than the landing limit of the level, between 1.4 and 2.0 m/s, and then stand still for half a second. A touchdown that is too hard costs damage and does not count: lift the parcel a little and set it down again.
The drone itself is easy to fly. The hard part is the load. The parcel hangs on a rope, so it swings like a pendulum whenever you speed up, brake or meet a gust of wind. Bring it in slowly and the swing stays small; rush, and the box swings into walls or overshoots the pad.
Each of the 20 levels adds something: a crane jib to fly under, a window cleaners' gondola, a heavier parcel, a longer rope, gusty wind, a patrol drone, a crane hoist that goes up and down, a low cloud base and a tiny pad on top of a tower. Finishing a level unlocks the next one. A level gives up to three stars: for finishing within the target time, for landing with enough battery left and for taking 10% damage or less.
Controls
- Keyboard: ↑ or W climbs, ↓ or S sinks, ← → or A D tilt the drone sideways. Let go and the drone brakes and hovers on its own. P or Esc pauses, R restarts, F switches full screen.
- Mouse: hold the left button where you want the drone to be. It flies toward the pointer and slows down as it gets close, so a point just below the drone gives a slow descent.
- Touch: four large buttons under the city tilt the drone and make it sink or climb, and they work together. You can also hold a finger on the city where the drone should fly. The page does not scroll while you play.
- The game pauses when you switch tabs, and after a delivery key presses are ignored for 0.7 seconds.
How it works
A pendulum under a moving drone
The rope cannot stretch but can go slack. When it is tight, the parcel is a pendulum hanging from the drone, and for small swings its period depends only on the rope length L and gravity g:
T = 2π · √(L / g)
A 3 m rope swings back and forth in about 3.5 seconds, the 6 m rope of the “Long line” level in about 4.9 seconds. When the drone speeds up, the parcel lags behind; when it stops, the parcel keeps going and swings forward. To calm a swing, move the drone a little in the direction the parcel is moving, as crane operators do. Air drag slowly damps the swing as well.
The flight controller
The drone holds a speed. A key asks for up to 5 m/s sideways, 3 m/s up or 2.2 m/s down; the controller tilts the drone by up to 34° and sets the thrust to reach that speed, and it hovers when you let go. It also feels the pull of the rope and adds thrust for the weight of the parcel, but stopping the swing is up to you.
Battery and wind
A rotor needs more power the more it lifts. In the momentum theory of a hovering rotor the ideal power is P = T1.5 / √(2ρA), with thrust T, air density ρ and rotor disc area A. The game uses the same rule: lifting a parcel half as heavy as the drone takes 1.5 times the thrust of the bare drone and 1.51.5 ≈ 1.8 times its power. The battery is sized for each job, and climbing and fighting the wind cost extra. Wind pushes on the drone and even more on the parcel, which is why gusts make the load swing. The arrow in the top left corner shows the wind and says Gust while a gust is blowing.
Tips
- Hover above the parcel and sink slowly until the hook catches it, then climb before you fly sideways.
- Start and stop gently. Short taps on a key give small, smooth moves.
- Stop above the pad, wait for the swing to settle, then tap ↓. The vertical speed of the parcel is shown next to it near the pad.
- Pass moving obstacles right after they go by; each follows the dashed line drawn along its path.
- In wind, keep the drone a little upwind of where the parcel should land.
Frequently asked questions
Why did my parcel not count when it touched the pad?
It came down faster than the landing limit, or too little of the box was on the pad. Lift it a little, let it stop swinging and set it down again.
Can the rope get caught on buildings?
No. Only the drone, the hook and the parcel collide with things; the rope passes through.
What happens when the battery runs out?
The motors stop and the drone falls, so the level is lost. A warning appears at 20%.
Sources
- Ling SJ, Sanny J, Moebs W (2016). 15.4 Pendulums. University Physics Volume 1, OpenStax. The period of a simple pendulum, T = 2π√(L / g), for small swings.
- Wikipedia contributors (accessed 25 October 2026). Momentum theory. Wikipedia. Encyclopedia article. The ideal power a hovering rotor needs for a given thrust, P = √(T³ / (2ρA)), the same rule as T1.5 / √(2ρA).