CSS3 spinner, preloader - css

Question

I would like to build a animated spinner with CSS3.
It should behave like this :
After the last state it should start again like in the first state.
I managed to create circles using the technique explained here : stackoverflow question
Now, how can I animate the spinner between the described states? I do not know how to animate the clip-rect property. I also guess that it would behave better with a clip-poly instead (a triangle maybe) but I can't animate that either.

Answer 1

CSS3 spinner
This CSS preloader uses keyframe animations and transform-rotate CSS3 properties to make the circle and the filling color.
This spinner is responsive.
.sp1 {
margin: 50px auto;
position: relative;
width: 30%;
padding-bottom: 30%;
overflow: hidden;
background-color: #557733;
border-radius: 50%;
z-index: 1;
}
.sp:before,
.sp:after {
content: '';
position: absolute;
height: 100%;
width: 50%;
background-color: #99FF33;
}
.sp1:after {
width: 80%;
height: 80%;
margin: 10%;
border-radius: 50%;
background-color: #fff;
z-index: 6;
}
.sp1:before {
background-color: inherit;
z-index: 5;
}
.sp2:before {
z-index: 4;
-webkit-animation: spin1 3s linear infinite;
animation: spin1 3s linear infinite;
-webkit-transform-origin: 100% 50%;
transform-origin: 100% 50%;
}
.sp2:after {
opacity: 0;
right: 0;
z-index: 6;
-webkit-animation: spin2 3s linear infinite;
animation: spin2 3s linear infinite;
-webkit-transform-origin: 0 50%;
transform-origin: 0 50%;
}
#-webkit-keyframes spin1 {
0% { -webkit-transform: rotate(0deg); }
50%, 100% { -webkit-transform: rotate(180deg); }
}
#keyframes spin1 {
0% { transform: rotate(0deg); }
50%, 100% { transform: rotate(180deg); }
}
#-webkit-keyframes spin2 {
0% { -webkit-transform: rotate(0deg); opacity: 0; }
49.99% { opacity: 0; }
50% { -webkit-transform: rotate(0deg); opacity: 1; }
100% { -webkit-transform: rotate(180deg); opacity: 1;
}
}
#keyframes spin2 {
0% { transform: rotate(0deg); opacity: 0; }
49.99% { opacity: 0; }
50% { transform: rotate(0deg); opacity: 1; }
100% { transform: rotate(180deg); opacity: 1; }
}
<div class="sp sp1">
<div class="sp sp2"></div>
</div>
Fiddle demo