How do I make a CSS Rotating Animation? - css

Question

I'm trying to make a css rotation animation that has different speeds at different degree points.
Here is the animation I'm trying to make:
Here is a Pen of what I currently have and below is the code:
img {
width: 125px;
}
body {
text-align: center;
}
#loading {
-webkit-animation: slow 1.5s linear 1.5s, fast 1s linear 1s, slow2 1s linear 1s;
-webkit-animation-iteration-count: infinite;
}
#-webkit-keyframes slow {
from {
-webkit-transform: rotate(0deg)
}
to {
-webkit-transform: rotate(90deg)
}
}
#-webkit-keyframes fast {
from {
-webkit-transform: rotate(91deg)
}
to {
-webkit-transform: rotate(270deg)
}
}
#-webkit-keyframes slow2 {
from {
-webkit-transform: rotate(271deg)
}
to {
-webkit-transform: rotate(359deg)
}
}
<img id="loading" src="https://i.imgur.com/VpLRlbZ.png">

Answer 1

So, in the example you provided, the effect is only done by modifying the animation-timing-function css property.
Then you'll have only one animation
div {
width:100px;
height:100px;
background:red;
animation:rotate 3s infinite;
animation-timing-function: cubic-bezier(1,0,.5,1);
}
#-webkit-keyframes rotate {
from { -webkit-transform: rotate(0deg) }
to { -webkit-transform: rotate(360deg) }
}
<div></div>
You can find more informations here : https://callmenick.com/dev/level-up-animations-cubic-bezier/
But the point is, use only one animation and modify speed at different angles value modifying this animation-timing-function.
EDIT Added a closer cubic bezier timing function thanks to #SirExotic comment.

Answer 2

You can just divide the animation keyframes into several ones, and adjust the percentages of each to set the relative speeds:
The natural percentage for 90deg would be 25% . Any value higher than that will make this part slower
img {
width: 125px;
}
body {
text-align: center;
}
#loading {
animation: rotate 4s linear infinite;
}
#keyframes rotate {
0% {
transform: rotate(0deg)
}
40% {
transform: rotate(90deg)
}
60% {
transform: rotate(270deg)
}
100% {
transform: rotate(360deg)
}
}
<img id="loading" src="https://i.imgur.com/VpLRlbZ.png">