Workshop › Lunar Lander › Step 17 of 31

Fuel

What we are doing

Fuel makes every burn a decision. The tank holds 400; each frame of engine uses 1, and an empty tank stops the engine.

```js
lander = { x: 60, y: 40, vx: 1, vy: 0, angle: 0, fuel: 400 }

return state === 'flying' && keys.ArrowUp && lander.fuel > 0

  lander.fuel -= 1
```

What it means

• The lander gets fuel: 400.
• burning() also needs fuel left, so an empty tank means no push and no flame.
• Every frame of burning uses 1.

Your turn

1. In reset, add fuel: 400 to the lander.
2. In burning, add && lander.fuel > 0.
3. In update, inside the if (burning()) block, write lander.fuel -= 1 at the end.

Skills: Game states

← A flickering flame Touch controls →

All steps

1. Random hills
2. Draw the hills
3. A landing pad
4. The height at any x
5. The lander
6. Draw it around its own middle
7. Two feet
8. The game loop
9. Moon gravity
10. Around the sides
11. Flying or not
12. Touching the ground
13. Remember held keys
14. Tilt
15. The engine
16. A flickering flame
17. Fuel
18. Touch controls
19. Landing or crashing
20. Fly again
21. Landed or crashed?
22. Readouts
23. Levels
24. Score
25. Next level or new game
26. A narrower pad
27. A high score
28. Burst into pieces
29. Pieces fall and fade
30. Draw the wreck
31. Build it yourself: wind