Workshop › Asteroids › Step 15 of 41

A lifetime for bullets

What we are doing

Bullets wrap, so they never leave the screen and cannot just be removed there. Instead each one's life counts down, and at 0 it is dropped: filter keeps only the bullets that still have life.

```js
  bullet.life -= 1

bullets = bullets.filter((bullet) => bullet.life > 0)
```

What it means

• Each frame every bullet loses 1 life.
• filter builds a new list with only the bullets whose life is above 0, and we put it in bullets.

Your turn

1. In the bullet loop, under the two moving lines, write bullet.life -= 1.
2. Under the loop's closing } write the filter line.

Skills: Arrays and objects

← Bullets fly Making a rock →

All steps

1. Black space
2. Where the ship is
3. Which way it points
4. A triangle ship
5. Which keys are down?
6. Turning
7. The game loop
8. Thrust and drift
9. A little friction
10. A speed limit
11. Around the screen
12. Making a bullet
13. Fire!
14. Bullets fly
15. A lifetime for bullets
16. Making a rock
17. Four big rocks
18. Drawing the rocks
19. Jagged rocks
20. Drifting rocks
21. When do two circles touch?
22. Breaking a rock
23. Bullets hit rocks
24. Points
25. Show the score
26. Losing a life
27. A rock hits the ship
28. Show the lives
29. What time is it?
30. A moment of safety
31. Blink while safe
32. Waves of rocks
33. The next wave
34. Faster every wave
35. One function to start
36. Playing or over
37. Game over
38. Best score
39. GAME OVER
40. Play again
41. Build it yourself: hyperspace