Workshop › Pinball › Step 37 of 42

Pull the spring

What we are doing

The longer you hold, the harder the launch. While the ball waits and the key is held, charge grows from 0 to 1 in about a second; letting go launches at a speed between 13 and 19.

```js
let charge // 0 to 1 while the launcher is held

  charge = 0

    if (pressed.launch) charge = Math.min(1, charge + 0.02)

  ball.vy = -(13 + 6 * charge)
  charge = 0
```

What it means

• newBall resets charge for each new ball.
• In the ready block, holding adds 0.02 a frame; Math.min(1, ...) stops it at 1 (50 frames, under a second).
• launch turns the charge into speed and empties the spring.

Your turn

1. Under let pressed write let charge.
2. In newBall, under the ball = ... line, write charge = 0.
3. In update's ready block, under the flippers line, write the charge line.
4. In launch, replace ball.vy = -16 with the two lines.

Skills: Velocity and gravity, Keyboard and mouse input

← Launch on letting go Show the spring →

All steps

1. Paint the table
2. Draw one wall
3. A list of walls
4. The game loop
5. A ball in the lane
6. Draw the ball
7. Move by the velocity
8. Launch with Space
9. Gravity
10. Does the ball touch a wall?
11. Push the ball out
12. Bounce off the wall
13. Small steps and a speed limit
14. Ready or playing
15. The next ball
16. Three bumpers
17. The ball meets a bumper
18. A bumper kicks
19. A score and a fresh start
20. Points for every hit
21. Remember which bumper was hit
22. Light it up
23. Lit for a moment, points once
24. Two flippers
25. Where is the tip?
26. Flippers stop the ball
27. Which keys are held?
28. Which way to turn
29. Flip!
30. A moving wall
31. The flipper throws
32. Three balls
33. Balls left and game over
34. Play again
35. Remember the best score
36. Launch on letting go
37. Pull the spring
38. Show the spring
39. Two thumbs
40. Pull with a finger
41. Tap to play again
42. Build it yourself: slingshots