Workshop › Angry Birds-style Slingshot › Step 14 of 47

Aiming or flying

What we are doing

Pressing Space twice launches two birds. The game needs to know what it is doing: a state of 'aiming' or 'flying'. You can only launch while aiming.

```js
let state // 'aiming' or 'flying'

  state = 'aiming'

function launch() {
  if (state !== 'aiming') return
  ...
  bodies.push(bird)
  state = 'flying'
}
```

What it means

• state holds one of two words.
• if (state !== 'aiming') return leaves launch at once unless we are aiming. !== means "is not equal to".
• After the launch the state becomes 'flying', so a second Space does nothing.

Your turn

1. Under let aim write let state.
2. In reset, under aim = ..., write state = 'aiming'.
3. In launch, write the if as the first line and state = 'flying' under bodies.push(bird).

Skills: Game states

← Land on the ground An empty sling in flight →

All steps

1. The sling
2. Sky and ground
3. Draw it again and again
4. The aim: an angle and a pull
5. A bird in the sling
6. Pull the bird back
7. The rubber band
8. Aim with the arrow keys
9. Bodies
10. Launch!
11. Move by the velocity
12. Gravity
13. Land on the ground
14. Aiming or flying
15. An empty sling in flight
16. Gone off the screen
17. Wait for calm
18. The next bird
19. See the path before you shoot
20. From a point to an aim
21. Grab the sling
22. Drag and let go
23. Wood and stone
24. A level as data
25. Push overlapping boxes apart
26. Bounce by mass
27. Every pair meets
28. Friction
29. Smaller steps
30. Hit points
31. Hard hits hurt
32. Things break
33. Pigs
34. Score
35. Show the score
36. Cracks
37. Three birds
38. Count the birds
39. Won or lost
40. The end panel
41. Play again
42. Three levels of data
43. Start any level
44. On to the next level
45. The best score
46. The right words
47. Build it yourself: the yellow bird