CSS3动画：5种预载动画效果实例

#preloader-5{
position: relative;
}
#preloader-5 span{
position:absolute;
width:50px;
height: 50px;
border:5px solid #fff;
border-radius: 999px;
opacity: 0;
animation: radar 2s infinite linear;
}
#preloader-5 span:nth-child(1){
animation-delay: 0s;
}
#preloader-5 span:nth-child(2){

animation-delay: 0.66s;
}
#preloader-5 span:nth-child(3){
animation-delay: 1.33s;
}

@keyframes radar{
0%{transform: scale(0);opacity: 0;}
25%{transform: scale(0);opacity: 0.5;}
50%{transform: scale(1);opacity: 1.0;}
75%{transform: scale(1.5);opacity: 0.5;}
100%{transform: scale(2);opacity: 0;}
}