freeCodeCamp/curriculum/challenges/english/01-responsive-web-design/applied-visual-design/create-movement-using-css-animation.english.md

id, title, challengeType, videoUrl

id	title	challengeType	videoUrl
587d78a7367417b2b2512ae1	Create Movement Using CSS Animation	0	https://scrimba.com/c/c7amZfW

Description

When elements have a specified position, such as fixed or relative, the CSS offset properties right, left, top, and bottom can be used in animation rules to create movement. As shown in the example below, you can push the item downwards then upwards by setting the top property of the 50% keyframe to 50px, but having it set to 0px for the first (0%) and the last (100%) keyframe.

@keyframes rainbow {
  0% {
    background-color: blue;
    top: 0px;
  }
  50% {
    background-color: green;
    top: 50px;
  }
  100% {
    background-color: yellow;
    top: 0px;
  }
}

Instructions

Add a horizontal motion to the div animation. Using the left offset property, add to the @keyframes rule so rainbow starts at 0 pixels at 0%, moves to 25 pixels at 50%, and ends at -25 pixels at 100%. Don't replace the top property in the editor - the animation should have both vertical and horizontal motion.

Tests

tests:
  - text: The <code>@keyframes</code> rule for <code>0%</code> should use the <code>left</code> offset of 0px.
    testString: assert(code.match(/0%\s*?{\s*?background-color:\s*?blue;\s*?top:\s*?0(px)?;\s*?left:\s*?0(px)?;\s*?}/gi), 'The <code>@keyframes</code> rule for <code>0%</code> should use the <code>left</code> offset of 0px.');
  - text: The <code>@keyframes</code> rule for <code>50%</code> should use the <code>left</code> offset of 25px.
    testString: assert(code.match(/50%\s*?{\s*?background-color:\s*?green;\s*?top:\s*?50px;\s*?left:\s*?25px;\s*?}/gi), 'The <code>@keyframes</code> rule for <code>50%</code> should use the <code>left</code> offset of 25px.');
  - text: The <code>@keyframes</code> rule for <code>100%</code> should use the <code>left</code> offset of -25px.
    testString: assert(code.match(/100%\s*?{\s*?background-color:\s*?yellow;\s*?top:\s*?0(px)?;\s*?left:\s*?-25px;\s*?}/gi), 'The <code>@keyframes</code> rule for <code>100%</code> should use the <code>left</code> offset of -25px.');

Challenge Seed

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

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

@keyframes rainbow {
  0% {
    background-color: blue;
    top: 0px;

  }
  50% {
    background-color: green;
    top: 50px;

  }
  100% {
    background-color: yellow;
    top: 0px;

  }
}
</style>

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

Solution

var code = "@keyframes rainbow {0% {background-color: blue; top: 0px; left: 0px;} 50% {background-color: green; top: 50px; left: 25px;} 100% {background-color: yellow; top: 0px; left:-25px;}}"