Workshop › Angry Birds-style Slingshot › Step 17 of 47

Wait for calm

What we are doing

When is a shot over? When nothing has moved for a while. calm counts the frames in a row in which no body is moving; any movement sets it back to 0.

```js
let calm // frames everything has been still

  calm = 0

function update() {
  step()
  if (state !== 'flying') return
  // Wait until everything has stopped for a second before the next bird.
  const moving = bodies.some((b) => Math.abs(b.vx) > 0.1 || Math.abs(b.vy) > 0.3)
  calm = moving ? 0 : calm + 1
}
```

What it means

calm starts at 0 in reset and again at each launch.
bodies.some(f) is true if f is true for at least one body. Math.abs drops the sign, so a speed of -3 counts as 3.
moving ? 0 : calm + 1 picks the first value when moving is true, otherwise the second.

Your turn

Under let state write let calm.
Write calm = 0 in reset (under state = 'aiming') and in launch (under state = 'flying').
In update, under step(), write the four new lines.

Skills: Game states

← Gone off the screen The next bird →

All steps