centering div fixed position -no solution worked - html

Question

I just want to make a preloader that's positioned in the middle of the page.
Requirements:
position: fixed;
centered on the X-axis
It's just a div with class 'preloader' in body. Body is this div's direct parent, no other wrapper in between.
.preloader {
position: fixed;
display: inline-block;
z-index: 99;
top: 45%;
left: 50%;
width: 60px;
height: 60px;
-ms-transform: translateX(100px); /*100px just to test if it moved at all, initially had -50%, see list below*/
-webkit-transform: translateX(100px);
transform: translateX(100px);
//=====rest is just animation and aesthetics======
border: 3px solid #8A2EE6;
border-radius: 50%;
border-bottom: 3px solid black;
box-shadow: 0px 0px 20px 1px rgba(153, 102, 255, 0.5) inset, 0px 0px 20px 1px rgba(153, 102, 255, 0.5);
animation-name: rotatePreloader;
animation-duration: 0.65s;
animation-direction: normal;
animation-iteration-count: infinite;
animation-timing-function: linear;
transition: opacity 1s;
}
I've done:
display: block;
display: inline-block;
translateX(-50%);
translateX(30px);
translate(-50%, 0);
translate(30px, 0);
translate(-50%, -50%);
rearranging the transforms.. lol
took off -o & -mos
margin: 0 auto (worked with position: relative when I didn't need it to be fixed)
https://jsfiddle.net/goa3v2ke/#

Answer 1

You need to do like this, where you set top/left to 50% and then move them back with translate using the same value, int this case -50%.
Sample 1 now center it both horizontal and vertical, and by change the top/left values, you can move it in the direction you want, sample 2 has 33% as top value.
Update based on question edit
The small X/Y-axis offset is caused by the rotate being executed before the translate, so change your #keyframes rule to this, showed in sample 3 and an update of your fiddle
#keyframes rotatePreloader {
0% {
transform: translate(-50%, -50%) rotate(0deg);
}
100% {
transform: translate(-50%, -50%) rotate(360deg);
}
}
Sample 1
.preloader {
position: fixed;
display: inline-block;
z-index: 99;
top: 50%;
left: 50%;
width: 60px;
height: 60px;
transform: translate(-50%,-50%);
/*=====rest is just animation and aesthetics======*/
border: 3px solid #8A2EE6;
border-radius: 50%;
border-bottom: 3px solid black;
box-shadow: 0px 0px 20px 1px rgba(153, 102, 255, 0.5) inset, 0px 0px 20px 1px rgba(153, 102, 255, 0.5);
animation-name: rotatePreloader;
animation-duration: 0.65s;
animation-direction: normal;
animation-iteration-count: infinite;
animation-timing-function: linear;
transition: opacity 1s;
}
<div class="preloader"></div>
Sample 2
.preloader {
position: fixed;
display: inline-block;
z-index: 99;
top: 33%;
left: 50%;
width: 60px;
height: 60px;
transform: translate(-50%,-50%);
/*=====rest is just animation and aesthetics======*/
border: 3px solid #8A2EE6;
border-radius: 50%;
border-bottom: 3px solid black;
box-shadow: 0px 0px 20px 1px rgba(153, 102, 255, 0.5) inset, 0px 0px 20px 1px rgba(153, 102, 255, 0.5);
animation-name: rotatePreloader;
animation-duration: 0.65s;
animation-direction: normal;
animation-iteration-count: infinite;
animation-timing-function: linear;
transition: opacity 1s;
}
<div class="preloader"></div>
Sample 3
.leftPreloaderBG {
position: fixed;
background-color: black;
width: 50%;
height: 100%;
z-index: 98;
top: 0px;
left: 0px;
transition: width 1s;
}
.leftPreloaderBG.loaded {
width: 0;
}
.rightPreloaderBG {
position: fixed;
background-color: black;
width: 50%;
height: 100%;
z-index: 98;
top: 0px;
right: 0px;
transition: width 1s;
}
.rightPreloaderBG.loaded {
width: 0;
}
#keyframes rotatePreloader {
0% {
transform: translate(-50%, -50%) rotate(0deg);
}
100% {
transform: translate(-50%, -50%) rotate(360deg);
}
}
.preloader {
position: fixed;
display: inline-block;
z-index: 99;
top: 33%;
left: 50%;
width: 60px;
height: 60px;
transform: translate(-50%, -50%);
/*=====rest is just animation and aesthetics======*/
border: 3px solid #8A2EE6;
border-radius: 50%;
border-bottom: 3px solid black;
box-shadow: 0px 0px 20px 1px rgba(153, 102, 255, 0.5) inset, 0px 0px 20px 1px rgba(153, 102, 255, 0.5);
animation-name: rotatePreloader;
animation-duration: 0.65s;
animation-direction: normal;
animation-iteration-count: infinite;
animation-timing-function: linear;
transition: opacity 1s;
}
.preloader.loaded {
opacity: 0;
}
* {
box-sizing: border-box;
margin: 0;
padding: 0;
}
body {
margin: 0;
padding: 0;
width: 100%;
color: white;
font-size: 1em;
background-color: gray;
background-position: center;
background-repeat: repeat;
}
<body>
<div class="preloader"></div>
<div class="leftPreloaderBG"></div>
<div class="rightPreloaderBG"></div>
</body>

Answer 2

It is because you override the transform translate value in the keyframe animation. Try it like this:
.leftPreloaderBG {
position: fixed;
background-color: black;
width: 50%;
height: 100%;
z-index: 98;
top: 0px;
left: 0px;
transition: width 1s;
}
.leftPreloaderBG.loaded {
width: 0;
}
.rightPreloaderBG {
position: fixed;
background-color: black;
width: 50%;
height: 100%;
z-index: 98;
top: 0px;
right: 0px;
transition: width 1s;
}
.rightPreloaderBG.loaded {
width: 0;
}
#keyframes rotatePreloader {
0% {
transform: translate(-50%, -50%) rotate(0deg);
}
100% {
transform: translate(-50%, -50%) rotate(360deg);
}
}
.preloader {
position: fixed;
display: inline-block;
z-index: 99;
top: 33%;
left: 50%;
width: 60px;
height: 60px;
transform: translate(-50%, -50%);
/*=====rest is just animation and aesthetics======*/
border: 3px solid #8A2EE6;
border-radius: 50%;
border-bottom: 3px solid black;
box-shadow: 0px 0px 20px 1px rgba(153, 102, 255, 0.5) inset, 0px 0px 20px 1px rgba(153, 102, 255, 0.5);
animation-name: rotatePreloader;
animation-duration: 0.65s;
animation-direction: normal;
animation-iteration-count: infinite;
animation-timing-function: linear;
transition: opacity 1s;
}
.preloader.loaded {
opacity: 0;
}
* {
box-sizing: border-box;
margin: 0;
padding: 0;
}
body {
margin: 0;
padding: 0;
width: 100%;
color: white;
font-size: 1em;
background-color: gray;
background-position: center;
background-repeat: repeat;
}
<body>
<div class="preloader"></div>
<div class="leftPreloaderBG"></div>
<div class="rightPreloaderBG"></div>
</body>