Workshop › Tower Defense › Step 41 of 42

Splash damage

What we are doing

The cannon's shot now hurts every enemy within its splash distance of the target. Arrows have a splash of 0, so they still hit only their target.

```js
const center = pointAt(bullet.target.d)
for (const e of enemies) {
  const p = pointAt(e.d)
  const close = e === bullet.target || Math.hypot(p.x - center.x, p.y - center.y) <= kind.splash
  if (close) e.hp -= kind.damage
}
```

What it means

• center is where the target is on the map.
• Math.hypot(dx, dy) is the straight-line distance between two points (Pythagoras).
• An enemy is hit if it is the target itself or close enough to it.

Your turn

In hit, replace the bullet.target.hp -= kind.damage line with the new lines.

Skills: Collision detection

← Tower buttons Build it yourself: sell a tower →

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