Workshop › Tower Defense › Step 27 of 42

Build, then defend

What we are doing

Tower defense has a rhythm: build, then defend, then build again. state is 'building' or 'wave'. While building no enemies come; startWave sends the next wave of 6 + 2 × wave enemies.

```js
let wave

let state // 'building', 'wave' or 'over'

  wave = 0
  toSpawn = 0
  spawnIn = 0
  state = 'building'

function startWave() {
  wave += 1
  toSpawn = 6 + wave * 2
  spawnIn = 0
  state = 'wave'
}

  if (state === 'wave' && toSpawn > 0) {
```

What it means

• The game now starts building, with no enemies to come.
• startWave counts the wave up, sets how many will come, and switches to 'wave'.
• Enemies only spawn during a wave.

Your turn

1. Above let toSpawn write let wave; under let spawnIn write let state.
2. In reset, write wave = 0 above toSpawn, change toSpawn = 30 to 0, and write state = 'building' under spawnIn = 0.
3. Under pointAt write startWave.
4. In update, add state === 'wave' && to the spawning if.

Skills: Game states

← Health bars Space starts a wave →

All steps

1. Measure the map
2. A map of tiles
3. Draw it every frame
4. The road as corners
5. Fill in the road
6. Draw the road
7. Walking by distance
8. Enemies on the road
9. Walk
10. Off the end of the road
11. Here they come
12. Towers
13. From a click to a tile
14. Click to build
15. Where can you build?
16. Show the gold
17. Show before you click
18. Show the range
19. Pick a target
20. Fire!
21. A hit hurts
22. Homing bullets
23. Fizzle out
24. Gold for every kill
25. Lives
26. Health bars
27. Build, then defend
28. Space starts a wave
29. The wave is over
30. Stronger every wave
31. Closer together
32. Out of lives
33. No building after the end
34. The most waves survived
35. The game over screen
36. Play again
37. The bottom bar
38. Click to start
39. A second tower: the cannon
40. Tower buttons
41. Splash damage
42. Build it yourself: sell a tower