90 lines
4.1 KiB
Markdown
90 lines
4.1 KiB
Markdown
---
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id: 587d78a9367417b2b2512ae9
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title: Use a Bezier Curve to Move a Graphic
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challengeType: 0
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videoUrl: 'https://scrimba.com/c/c6bnRCK'
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---
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## Description
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<section id='description'>
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A previous challenge discussed the <code>ease-out</code> keyword that describes an animation change that speeds up first and then slows down at the end of the animation. On the right, the difference between the <code>ease-out</code> keyword (for the blue element) and <code>linear</code> keyword (for the red element) is demonstrated. Similar animation progressions to the <code>ease-out</code> keyword can be achieved by using a custom cubic Bezier curve function.
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In general, changing the <code>p1</code> and <code>p2</code> anchor points drives the creation of different Bezier curves, which controls how the animation progresses through time. Here's an example of a Bezier curve using values to mimic the ease-out style:
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<code>animation-timing-function: cubic-bezier(0, 0, 0.58, 1);</code>
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Remember that all <code>cubic-bezier</code> functions start with <code>p0</code> at (0, 0) and end with <code>p3</code> at (1, 1). In this example, the curve moves faster through the Y-axis (starts at 0, goes to <code>p1</code> y value of 0, then goes to <code>p2</code> y value of 1) than it moves through the X-axis (0 to start, then 0 for <code>p1</code>, up to 0.58 for <code>p2</code>). As a result, the change in the animated element progresses faster than the time of the animation for that segment. Towards the end of the curve, the relationship between the change in x and y values reverses - the y value moves from 1 to 1 (no change), and the x values move from 0.58 to 1, making the animation changes progress slower compared to the animation duration.
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</section>
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## Instructions
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<section id='instructions'>
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To see the effect of this Bezier curve in action, change the <code>animation-timing-function</code> of the element with id of <code>red</code> to a <code>cubic-bezier</code> function with x1, y1, x2, y2 values set respectively to 0, 0, 0.58, 1. This will make both elements progress through the animation similarly.
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: The value of the <code>animation-timing-function</code> property of the element with the id <code>red</code> should be a <code>cubic-bezier</code> function with x1, y1, x2, y2 values set respectively to 0, 0, 0.58, 1 .
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testString: assert($('#red').css('animation-timing-function') == 'cubic-bezier(0, 0, 0.58, 1)', 'The value of the <code>animation-timing-function</code> property of the element with the id <code>red</code> should be a <code>cubic-bezier</code> function with x1, y1, x2, y2 values set respectively to 0, 0, 0.58, 1 .');
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- text: The element with the id <code>red</code> should no longer have the <code>animation-timing-function</code> property of linear.
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testString: assert($('#red').css('animation-timing-function') !== 'linear', 'The element with the id <code>red</code> should no longer have the <code>animation-timing-function</code> property of linear.');
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- text: The value of the <code>animation-timing-function</code> property for the element with the id <code>blue</code> should not change.
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testString: assert($('#blue').css('animation-timing-function') == 'ease-out', 'The value of the <code>animation-timing-function</code> property for the element with the id <code>blue</code> should not change.');
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='html-seed'>
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```html
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<style>
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.balls{
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border-radius: 50%;
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position: fixed;
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width: 50px;
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height: 50px;
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margin-top: 50px;
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animation-name: bounce;
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animation-duration: 2s;
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animation-iteration-count: infinite;
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}
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#red {
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background: red;
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left: 27%;
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animation-timing-function: linear;
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}
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#blue {
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background: blue;
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left: 56%;
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animation-timing-function: ease-out;
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}
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@keyframes bounce {
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0% {
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top: 0px;
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}
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100% {
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top: 249px;
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}
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}
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</style>
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<div class="balls" id= "red"></div>
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<div class="balls" id= "blue"></div>
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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// solution required
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```
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</section>
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