Workshop › Asteroids › Step 32 of 41

Waves of rocks

What we are doing

The rocks come in waves: wave 1 has 4, and every wave one more (3 + wave). spawnWave builds a wave at the left or top edge, away from the ship. It replaces the start-up code for the rocks.

```js
let wave

function spawnWave() {
  asteroids = []
  for (let i = 0; i < 3 + wave; i++) {
    // Start at the edges, away from the ship in the middle.
    const edge = Math.random() < 0.5
    const x = edge ? 0 : Math.random() * canvas.width
    const y = edge ? Math.random() * canvas.height : 0
    asteroids.push(makeAsteroid(x, y, 3))
  }
}

wave = 1
spawnWave()
```

What it means

edge is a coin toss: true puts the rock on the left edge at a random height, false on the top edge at a random x.
At the bottom, wave = 1 and spawnWave() replace the two old rock lines.

Your turn

Under let lives write let wave.
Above function shoot() { write spawnWave, followed by an empty line.
At the bottom, replace the asteroids = [] and for lines with wave = 1 and spawnWave().

Skills: Game states

← Blink while safe The next wave →

All steps