freeCodeCamp/curriculum/challenges/english/01-responsive-web-design/applied-visual-design/learn-how-the-css-keyframes-and-animation-properties-work.english.md

id	title	challengeType	videoUrl
587d78a7367417b2b2512adf	Learn How the CSS @keyframes and animation Properties Work	0	https://scrimba.com/c/cakprhv

Description

To animate an element, you need to know about the animation properties and the @keyframes rule. The animation properties control how the animation should behave and the @keyframes rule controls what happens during that animation. There are eight animation properties in total. This challenge will keep it simple and cover the two most important ones first: animation-name sets the name of the animation, which is later used by @keyframes to tell CSS which rules go with which animations. animation-duration sets the length of time for the animation. @keyframes is how to specify exactly what happens within the animation over the duration. This is done by giving CSS properties for specific "frames" during the animation, with percentages ranging from 0% to 100%. If you compare this to a movie, the CSS properties for 0% is how the element displays in the opening scene. The CSS properties for 100% is how the element appears at the end, right before the credits roll. Then CSS applies the magic to transition the element over the given duration to act out the scene. Here's an example to illustrate the usage of @keyframes and the animation properties:

#anim {
  animation-name: colorful;
  animation-duration: 3s;
}

@keyframes colorful {
  0% {
    background-color: blue;
  }
  100% {
    background-color: yellow;
  }
}

For the element with the anim id, the code snippet above sets the animation-name to colorful and sets the animation-duration to 3 seconds. Then the @keyframes rule links to the animation properties with the name colorful. It sets the color to blue at the beginning of the animation (0%) which will transition to yellow by the end of the animation (100%). You aren't limited to only beginning-end transitions, you can set properties for the element for any percentage between 0% and 100%.

Instructions

Create an animation for the element with the id rect, by setting the animation-name to rainbow and the animation-duration to 4 seconds. Next, declare a @keyframes rule, and set the background-color at the beginning of the animation (0%) to blue, the middle of the animation (50%) to green, and the end of the animation (100%) to yellow.

Tests

tests:
  - text: The element with id of <code>rect</code> should have an <code>animation-name</code> property with a value of rainbow.
    testString: assert($('#rect').css('animation-name') == 'rainbow');
  - text: The element with id of <code>rect</code> should have an <code>animation-duration</code> property with a value of 4s.
    testString: assert($('#rect').css('animation-duration') == '4s');
  - text: The <code>@keyframes</code> rule should use the <code>animation-name</code> of rainbow.
    testString: assert(code.match(/@keyframes\s+?rainbow\s*?{/g));
  - text: The <code>@keyframes</code> rule for rainbow should use a <code>background-color</code> of blue at 0%.
    testString: assert(code.match(/0%\s*?{\s*?background-color:\s*?blue;\s*?}/gi));
  - text: The <code>@keyframes</code> rule for rainbow should use a <code>background-color</code> of green at 50%.
    testString: assert(code.match(/50%\s*?{\s*?background-color:\s*?green;\s*?}/gi));
  - text: The <code>@keyframes</code> rule for rainbow should use a <code>background-color</code> of yellow at 100%.
    testString: assert(code.match(/100%\s*?{\s*?background-color:\s*?yellow;\s*?}/gi));

Challenge Seed

<style>
  div {
    height: 40px;
    width: 70%;
    background: black;
    margin: 50px auto;
    border-radius: 5px;
  }

  #rect {


  }




</style>
<div id="rect"></div>

Solution

<style>
  div {
    height: 40px;
    width: 70%;
    background: black;
    margin: 50px auto;
    border-radius: 5px;
  }

  #rect {
    animation-name: rainbow;
    animation-duration: 4s;
  }

  @keyframes rainbow {
    0% {
      background-color: blue;
    }
    50% {
      background-color: green;
    }
    100% {
      background-color: yellow;
    }
  }
</style>
<div id="rect"></div>