body {
	display: flex;            /*弹性布局*/
    text-align: center;       /*文本水平居中*/
	justify-content: center;  /* 水平居中 */
	background-color: #e7e7e7; /*面板颜色为浅灰色*/
    font: normal 100% Helvetica, Arial, sans-serif;margin: 0;padding: 0;}   
 h1 {font-size: 1.6em;}   
 .container {
	 width: 100%;
     max-width: 1200px;
	 margin: 0 auto;
	 padding: 20px;} 	 
 .column {
	 width: 100%;
	 float: left;
	 padding: 10px;} 	  
 @media screen and 
        (max-width: 720px) {
 .container {width: 90% !important;
           padding: 10px !important;}
    .column {width: 100%;}}
.window-header::before,
.window-header::after {
    content: '';
    position: absolute;
    top: -2px;
    left: -2px;
    right: -2px;
    bottom: -2px;
    z-index: -1;
    border: 1px solid transparent;
    transition: all 0.2s ease-in-out;}
.window-header::before {
    border-top-color: #ffffff;
    border-left-color: #ffffff;}
.window-header::after {
    border-right-color: #a0a0a0;
    border-bottom-color: #a0a0a0;}	
.button {
    background-color: #e0e0e0;
    border: 2px solid #a0a0a0;
    padding: 7px 18px; 
    font-size: 14px;
    cursor: pointer;
    position: relative;
    margin: 5px;}
.button::before,
.button::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    border: 1px solid transparent;
    transition: all 0.2s ease-in-out;}
.button::before {
    border-top-color: #ffffff;
    border-left-color: #ffffff;}
.button::after {
    border-right-color: #a0a0a0;
    border-bottom-color: #a0a0a0;}
.button:hover {
    background-color: #b0b0b0;}
.button:active {
    background-color: #808080;
    transform: translate(1px, 1px);}
.button.clicked {
    background-color: #00ffff;}