Workshop › Pool › Step 30 of 33

Draw the ghost ball

What we are doing

While aiming, the aim line now ends at the ghost ball, and an outlined circle shows where the cue ball will touch.

```js
const g = ghost()
const length = g ? g.hit : 400

ctx.lineTo(cue.x + Math.cos(aim) * length, cue.y + Math.sin(aim) * length)
ctx.stroke()
if (g) {
  ctx.beginPath()
  ctx.arc(g.x, g.y, R, 0, Math.PI * 2)
  ctx.stroke()
}
```

What it means

• length is the distance to the ghost ball, or 400 when nothing is in the way.
• stroke instead of fill draws only the outline of the circle.

Your turn

1. In draw, at the top of if (state === 'aiming') {, write the g and length lines.
2. In the lineTo line, replace both 400s with length.
3. Under ctx.stroke(), write the if (g) block.

Skills: Drawing on a canvas

← Predict the hit Where the hit ball goes →

All steps

1. The room
2. The table
3. The cue ball
4. Draw the balls
5. The rack
6. Numbers on the balls
7. An aim line
8. Turn the aim
9. A shot is a velocity
10. Roll
11. Friction
12. Cushions
13. Aiming and rolling
14. Hide the aim while rolling
15. Count the shots
16. Balls that touch
17. Swap the push
18. Six pockets
19. In the pocket
20. Scratch
21. Balls left
22. Clear the table
23. Choose the power
24. A power bar
25. A slingshot
26. Press to aim
27. Pull back and let go
28. Smaller steps
29. Predict the hit
30. Draw the ghost ball
31. Where the hit ball goes
32. Your best
33. Build it yourself: two players