body {  
                background-color: steelblue;  
                color: #fff;  
                font-family: 'Muli', 
                sans-serif;  
                display: flex;  
                flex-direction: column;  
                align-items: center;  
                /*justify-content: center;  h上下居中显示*/
                height: 100vh;  
                overflow: hidden;  
                margin: 0;
                
            }
            .log-main {
                background-color: rgba(0, 200, 100, 0.5);  /*RGBA的意思是（Red-Green-Blue-Alpha）它是在RGB上扩展包括了“alpha”通道，运行对颜色值设置透明度。在RGBA中，四个数字以逗号分隔开，*/
                padding: 20px 40px;  
                border-radius: 50px;
                margin-top: 5vh;
                
            }
            .log-main h1 {
                text-align: center;  
                margin-bottom: 30px;
                font-family: "Times New Roman", cursive,serif;
                
                
            }
            .log-main a {
                text-decoration: none;  /*设置文本的装饰线none：移除文本装饰线underline：添加下划线overline：添加上划线line-through：添加删除线inherit：从父元素继承文本装饰*/
                color: red;/*lightblue;*/
                font-weight: bold;/*boldernormal	默认值。定义标准的字符。bold：定义粗体字符。bolde：定义更粗的字符。lighter：定义更细的字符。100 200 300 400 500 600 700 800 900	定义由细到粗的字符。400 等同于 normal，而 700 等同于 bold。inherit	规定应该从父元素继承字体的粗细。*/
            }
            .log-main .text {
                text-align: right;
                padding-right: 20px ;
                margin-top: 30px;
            }
            .log-btn {  
                cursor: pointer;  
                display: inline-block;  
                width: 100%; 
                background: lightblue;  
                padding: 15px;  
                font-family: inherit;  
                font-size: 16px;  
                border: 0;  
                border-radius: 5px;
                
            }
            .log-btn a:hover {
                background:red; 
                font-size: 20px; 
                color: green;
            }
            .log-btn:focus {  outline: 0;}
            .log-btn:active {  
                transform: scale(0.96);/* 0-隐藏  1-默认 小于0缩放 大于1放大*/
                color: blue;
                background: #999;
            }
            
            .form-control {  
                position: relative;  /*设置元素定位的一种position: relative; left: 10px;这段文字将向右移动10像素但其原本的位置仍然占据在文档流中，不会影响其他元素的布局。*/
                margin: 20px 0 30px;  
                width: 300px;
                
            }
            .form-control input {  background-color: transparent; /*透明的*/ border: 0;  border-bottom: 2px #fff solid;  display: block;  width: 100%;  padding: 15px 0;  font-size: 18px;  color: #fff;}
            .form-control input:focus, .form-control input:valid {  outline: 0;  border-bottom-color: red;}
            .form-control label {  position: absolute;  top: 15px;  left: 0;  pointer-events: none;}
            .form-control label span {  display: inline-block;  font-size: 18px;  min-width: 5px;  transition: 0.3s cubic-bezier(0.68, -0.55, 0.265, 1.55);}
            .form-control input:focus + label span,.form-control input:valid + label span {  color: lightblue;  transform: translateY(-30px);}
            .form-log-yzm{
                width: 50%;
                text-align: center;
            }