The code is based on CSS3 's clip, transform, and animation, so you need to know exactly what these attributes are for the purpose of understanding the CSS principle.
Create a css file and named it as style.css and paste the following code.
CSS CODE:
.wrapper {
width: 100px; /* Set the size of the progress bar */
height: 100px;
position: absolute; /* Enable clipping */
clip: rect(0px, 100px, 100px, 50px); /* Hide half of the progress bar */
}
/* Set the sizes of the elements that make up the progress bar */
.circle {
width: 80px;
height: 80px;
border: 10px solid green;
border-radius: 50px;
position: absolute;
clip: rect(0px, 50px, 100px, 0px);
}
/* Using the data attributes for the animation selectors. */
/* Base settings for all animated elements */
div[data-anim~=base] {
-webkit-animation-iteration-count: 1; /* Only run once */
-webkit-animation-fill-mode: forwards; /* Hold the last keyframe */
-webkit-animation-timing-function: linear; /* Linear animation */
}
.wrapper[data-anim~=wrapper] {
-webkit-animation-duration: 0.01s; /* Complete keyframes asap */
-webkit-animation-delay: 3s; /* Wait half of the animation */
-webkit-animation-name: close-wrapper; /* Keyframes name */
}
.circle[data-anim~=left] {
-webkit-animation-duration: 6s; /* Full animation time */
-webkit-animation-name: left-spin;
}
.circle[data-anim~=right] {
-webkit-animation-duration: 3s; /* Half animation time */
-webkit-animation-name: right-spin;
}
/* Rotate the right side of the progress bar from 0 to 180 degrees */
@-webkit-keyframes right-spin {
from {
-webkit-transform: rotate(0deg);
}
to {
-webkit-transform: rotate(180deg);
}
}
/* Rotate the left side of the progress bar from 0 to 360 degrees */
@-webkit-keyframes left-spin {
from {
-webkit-transform: rotate(0deg);
}
to {
-webkit-transform: rotate(360deg);
}
}
/* Set the wrapper clip to auto, effectively removing the clip */
@-webkit-keyframes close-wrapper {
to {
clip: rect(auto, auto, auto, auto);
}
HTML CODE:
Refer the style.css to the page.
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Pure CSS for circular animation</title>
<link href="~/css/style.css" rel="stylesheet" />
</head>
<body>
<div class="wrapper" data-anim="base wrapper">
<div class="circle" data-anim="base left"></div>
<div class="circle" data-anim="base right"></div>
</div>
</body>
</html>
Operation:
First of all: define three animations, the first is the outermost layer, let him only show half, then run 3s, while the right side runs 3s, from 0 to 180 degrees.
Then: After 180 degrees, release the display half of the outer layer and let him automatically display the other. Then stop the animation on the right and stop there.
Finally: the left side is on the original basis (3s running the same as the right side, also rotated 180 degrees) and then continues to rotate 180 degrees.