* {
    margin: 0;
    padding: 0;
}

html, body {
    height: 100%;
    width: 100%;
}

a {
    text-decoration: none;
    color: #606266;
}

.header {
    display: flex;
    justify-content: space-around;
    height: 50px;
    background: #1F212E;
    color: #FFFFFF;
    line-height: 50px;
    cursor: pointer;
}

.header a {
    color: #b4b4b4;
    margin-right: 10px;
    text-decoration: none;
}

.header a:hover {
    color: #FFFFFF;
}

.header .center .user {
    display: flex;
    align-items: center;
}

.header .center img {
    width: 30px;
    height: 30px;
    border-radius: 5px;
    margin-right: 6px;
}

.mt_20 {
    margin-top: 20px;
}

.mt_30 {
    margin-top: 30px;
}

.mt_40 {
    margin-top: 40px;
}

.mt_50 {
    margin-top: 50px;
}

.mt_60 {
    margin-top: 60px;
}

.mt_70 {
    margin-top: 70px;
}

.mt_80 {
    margin-top: 80px;
}

.mt_90 {
    margin-top: 90px;
}

.flex_start {
    align-items: flex-start !important;
}