Workshop › Pool › Step 10 of 33

Roll

What we are doing

Every frame each ball moves by its velocity. step is one step of the physics; update runs it, and the loop calls update before draw.

```js
function step() {
  for (const b of balls) {
    b.x += b.vx
    b.y += b.vy
  }
}

function update() {
  step()
}

  update()
```

What it means

• step adds each ball's velocity to its position.
• loop now calls update() before draw().

Your turn

1. Above the key listener write step and update, each followed by an empty line.
2. In loop, call update() before draw(). Run and press Space.

Skills: Velocity and gravity, The game loop

← A shot is a velocity Friction →

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