SOURCE

<div class="login-bg">
    <div class="round">
    </div>
    <div class="icon-div">
        <div class="icon icon1"></div>
        <div class="icon icon2"></div>
        <div class="icon icon3"></div>
        <div class="icon icon4"></div>
    </div>
    <div class="icon-div-copy">
        <div class="icon icon1"></div>
        <div class="icon icon2"></div>
        <div class="icon icon3"></div>
        <div class="icon icon4"></div>
    </div>
</div>
<form class="form">
    <div class="title">后台登录系统</div>
    <div class="username">
        <input type="text" placeholder="请输入用户名">
    </div>
    <div class="pwd">
        <input type="text" placeholder="请输入密码">
    </div>
    <button class="btn" onclick="return false;">登录</button>
</form>

:root {
    --round-size: 24rem;
}

body {
    overflow: hidden;
    padding: 0px;
    margin: 0px;
}

/*背景 渐变部分*/
.login-bg {
    height: 100vh;
    width: 100vw;
    background: linear-gradient(180deg, #02aab0, #00cdac);
}

/*白色部分*/
.login-bg:before {
    content: "";
    position: absolute;
    right: -25%;
    top: -15%;
    height: 300%;
    width: 100%;
    background: #fff;
    transform: rotate(25deg);
}

/*圆圈*/
.round {
    position: absolute;
    top: 30%;
    left: 30%;
    width: var(--round-size);
    height: var(--round-size);
    border-radius: 50%;
    background: #00cdac;
    display: grid;
    justify-content: center;
    opacity: 0;
    animation-delay: .5s;
    animation-duration: .6s;
    animation-name: zoomIn1;
    animation-fill-mode: both;
}

/*小电脑*/
.round:before {
    content: "";
    --r-size: 6rem;
    width: calc(var(--round-size) - var(--r-size));
    height: calc(var(--round-size) - var(--r-size));
    /* border-radius:50%;
	background:#02aab0;
	*/
    background-image: url('http://gitee.com/shixixiyue/FineUICore_8.0_Login/raw/master/FineUICore.Examples/wwwroot/login/%E7%94%B5%E8%84%911.png');
    background-size: 100%;
    margin: auto;
    opacity: 0;
    animation-delay: .7s;
    animation-duration: .4s;
    animation-name: zoomIn2;
    animation-fill-mode: both;
}

/*圆圈动画*/
@keyframes zoomIn1 {
    from {
        opacity: 0;
        transform: scale3d(.3, .3, .3);
    }

    70% {
        transform: scale3d(1.2, 1.2, 1.2);
    }

    100% {
        transform: scale3d(1, 1, 1);
        opacity: 1;
    }
}

/*小电脑动画*/
@keyframes zoomIn2 {
    from {
        opacity: 0;
        transform: scale3d(.3, .3, .3);
    }

    100% {
        opacity: .8;
    }
}

/*小图标 图层*/
.icon-div,
.icon-div-copy {
    position: absolute;
    top: 30%;
    left: 30%;
    width: var(--round-size);
    height: var(--round-size);
}

/*图标*/
.icon {
    background-color: #fff;
    background-repeat: no-repeat;
    background-position: center;
    background-size: 80%;
    width: 5rem;
    height: 5rem;
    position: absolute;
    animation-duration: .4s;
    animation-name: fadeInUp;
    animation-fill-mode: both;
    border-radius: 50%;
    box-shadow: 0 2px 4px rgba(0, 0, 0, .12), 0 0 6px rgba(0, 0, 0, .04);
}

/* 图标延迟进入 */
.icon1 {
    background-image: url('http://gitee.com/shixixiyue/FineUICore_8.0_Login/raw/master/FineUICore.Examples/wwwroot/login/%E5%9B%BE%E6%A0%87/1.png');
    top: 41%;
    left: -15%;
    animation-delay: 1.2s;
}

.icon2 {
    background-image: url('http://gitee.com/shixixiyue/FineUICore_8.0_Login/raw/master/FineUICore.Examples/wwwroot/login/%E5%9B%BE%E6%A0%87/2.png');
    top: -3%;
    left: 3%;
    animation-delay: 1.4s;
}

.icon3 {
    background-image: url('http://gitee.com/shixixiyue/FineUICore_8.0_Login/raw/master/FineUICore.Examples/wwwroot/login/%E5%9B%BE%E6%A0%87/3.png');
    top: -1%;
    left: 42%;
    animation-delay: 1.5s;
}

.icon4 {
    background-image: url('http://gitee.com/shixixiyue/FineUICore_8.0_Login/raw/master/FineUICore.Examples/wwwroot/login/%E5%9B%BE%E6%A0%87/4.png');
    top: 15%;
    left: 84%;
    animation-delay: 1.7s;
}

/*图标进入*/
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translate3d(0, 30%, 0);
    }

    99% {
        opacity: 1;
    }

    /*进入后隐藏 由copy 继续动画*/
    100% {
        opacity: 0;
    }
}

/*copy图层*/
.icon-div-copy .icon {
    opacity: 0;
    animation: updown 1.5s infinite ease-in-out;
    animation-direction: alternate;
}

/*延迟进入*/
.icon-div-copy .icon1 {
    animation-delay: 1.5s;
}

.icon-div-copy .icon2 {
    animation-delay: 1.7s;
}

.icon-div-copy .icon3 {
    animation-delay: 1.8s;
}

.icon-div-copy .icon4 {
    animation-delay: 2.09s;
}

/*copy图标来回动*/
@keyframes updown {
    from {
        opacity: 1;
        transform: translate3d(0, 0%, 0);
    }

    1% {
        opacity: 1;
        transform: translate3d(0, 0%, 0);
    }

    100% {
        opacity: 1;
        transform: translate3d(0, -10%, 0);
    }
}

/*表单*/
.form {
    position: absolute;
    right: 10%;
    top: 28%;
    animation-duration: .8s;
    animation-delay: .5s;
    animation-name: fadeInRight;
    animation-fill-mode: both;
    animation-timing-function: ease-in;
    width: 30rem;
    height: 30rem;
    font-family: '微软雅黑';
}

.form>* {
    margin-bottom: 3rem;
}

/*标题*/
.form .title {
    color: #02aab0;
    font-size: 4rem;
    font-weight: 600;
    letter-spacing: 6px;
    line-height: 4rem;
}

/*输入框*/
.form .f-field-body.f-widget-content {
    background-color: #fff;
    border-color: #02aab0;
}

.form input {
    color: #333 !important;
    font-size: 1.5rem;
    line-height: 3rem;
    text-indent: 6px;
    width: 98%;
}

/*登录按钮*/
.form .btn {
    width: 100%;
    height: 4rem;
    border: none;
    background: linear-gradient(90deg, #02aab0, #00cdac);
    line-height: 3rem;
    font-size: 1.5rem;
    margin: 0;
    text-indent: 1rem;
    letter-spacing: 1rem;
    color: #fff;
    cursor: pointer;
}

/*表单进入动画*/
@keyframes fadeInRight {
    from {
        opacity: 0;
        transform: translate3d(30%, 0, 0);
    }

    to {
        opacity: 1;
        transform: none;
    }
}