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Interplanetary Postal Service
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About the game
You work for the Interplanetary Postal Service, and the mail has to get through. Your job is the last stretch of the delivery: take a small lander down to a colony and put it on the landing pad without crashing, with five ships to spend across eight levels.
What makes it different from the lunar lander you may know is the air. Instead of faking wind with a few numbers, the game solves the equations of fluid flow on a grid, and the result is what you see on screen: the exhaust of your thruster, the wind of the level and the puffs from explosions are coloured fluids that swirl, push each other and push you. Gusts that look harmless can tip the ship over, so the hardest part is learning to read the air.
Sebastian Macke wrote the simulation in C, compiled it to a tiny WebAssembly module and made the game for js13kGames 2018, where the whole game, zipped, had to fit in 13 kilobytes. His write-up on GitHub explains how the fluid, the collisions and the maps work.
Playing it here
Click Play and click inside the game, so it picks up the keyboard, then press any key to start. A short countdown runs before each level; then the lander is yours. You play with the keyboard only. The game runs on every modern desktop browser, but the fluid simulation needs some processing power, so a very old computer or a phone may be too slow.
Controls
| Key | Action |
|---|---|
| Up arrow / W | fire the thruster that pushes the lander up |
| Down arrow / S | push it down |
| Left / Right arrow (or A / D) | push it sideways |
| Space | sound on / off |
A few things worth knowing
Watch the fuel. The bar on the left shows what is left in the tank, and every thruster burns fuel. Short bursts save it, and the fuel you have left when you land counts towards your score.
Land slowly. The landing pad is the white bar on the ground. Touch down too fast and the lander explodes; the gauge on the right shows your vertical speed. A good landing even earns you a spare ship.
Read the wind. The colours in the air show where the wind goes. Wait for a gust to pass instead of fighting it.
Credits and licence
Interplanetary Postal Service was created by Sebastian Macke and released under the GNU General Public License, version 3. As the licence requires, the complete source code of this build (the C and JavaScript sources, the maps and the build script) is hosted here, together with the game, and is linked from this page. The original project is on GitHub.