---
id: 587d78a9367417b2b2512aea
title: Make Motion More Natural Using a Bezier Curve
challengeType: 0
videoUrl: 'https://scrimba.com/c/c7akWUv'
---
## Description
This challenge animates an element to replicate the movement of a ball being juggled. Prior challenges covered the linear
and ease-out
cubic Bezier curves, however neither depicts the juggling movement accurately. You need to customize a Bezier curve for this.
The animation-timing-function
automatically loops at every keyframe when the animation-iteration-count
is set to infinite. Since there is a keyframe rule set in the middle of the animation duration (at 50%
), it results in two identical animation progressions at the upward and downward movement of the ball.
The following cubic Bezier curve simulates a juggling movement:
cubic-bezier(0.3, 0.4, 0.5, 1.6);
Notice that the value of y2 is larger than 1. Although the cubic Bezier curve is mapped on an 1 by 1 coordinate system, and it can only accept x values from 0 to 1, the y value can be set to numbers larger than one. This results in a bouncing movement that is ideal for simulating the juggling ball.
## Instructions
Change value of the animation-timing-function
of the element with the id of green
to a cubic-bezier
function with x1, y1, x2, y2 values set respectively to 0.311, 0.441, 0.444, 1.649.
## Tests
```yml
tests:
- text: The value of the animation-timing-function
property for the element with the id green
should be a cubic-bezier
function with x1, y1, x2, y2 values as specified.
testString: assert($('#green').css('animation-timing-function') == 'cubic-bezier(0.311, 0.441, 0.444, 1.649)', 'The value of the animation-timing-function
property for the element with the id green
should be a cubic-bezier
function with x1, y1, x2, y2 values as specified.');
```
## Challenge Seed
## Solution
```js
// solution required
```