#Header {
    display: flex;
    font-weight:600;
    font-size: xx-large;	/* should be same as an h1 header */
    margin:20px 0 10px 0;
    padding:0 0 2.0ex 20px;
    border-style:solid;
    border-color:black;
    border-width:1px 0;
    background-color:#eee;
    text-align: center;

    /* Here is the ugly brilliant hack that protects IE5/Win from its own
stupidity.  Thanks to Tantek Celik for the hack and to Eric Costello
for publicizing it.  IE5/Win incorrectly parses the "\"}"" value,
prematurely closing the style declaration. The incorrect IE5/Win value
is above, while the correct value is below. See
http://glish.com/css/hacks.asp for details. */

    voice-family: "\"}\"";
    voice-family:inherit;
    height:1ex;	/* UNTESTED!  Was 14px */
}


@keyframes go-left-right {        /* 指定一个名字："go-left-right" */
    from { left: 0px; }             /* 从 left: 0px 开始 */
    to { left: calc(100% - 50px); } /* 移动至 left: 100%-50px */
}

.progress {
    animation: go-left-right 3s infinite alternate;

    position: relative;
    border: 2px solid green;
    width: 50px;
    height: 20px;
    background: lime;
}