img {
    user-select: none;       /* 标准语法 */
    -webkit-user-select: none; /* Safari/Chrome */
    -moz-user-select: none;    /* Firefox */
    -ms-user-select: none;     /* IE/Edge */
    -webkit-user-drag: none; /* Safari/Chrome */
    user-drag: none;
}

/******************************************** flex公用布局 ********************************************/

.flex {
    display: flex;
    flex-direction: row;
}

.flex-item {
    flex: 1;
}

.row {
    flex-direction: row;
}

.flex-column {
    flex-direction: column;
}

.flex-vc {
    -webkit-box-align: center;
    -webkit-align-items: center;
    -moz-align-items: center;
    -ms-align-items: center;
    -o-align-items: center;
    align-items: center;
}

.flex-vt {
    -webkit-align-items: flex-start;
    -moz-align-items: flex-start;
    -ms-align-items: flex-start;
    -o-align-items: flex-start;
    align-items: flex-start;
}

.flex-vb {
    -webkit-align-items: flex-end;
    -moz-align-items: flex-end;
    -ms-align-items: flex-end;
    -o-align-items: flex-end;
    align-items: flex-end;
}

.flex-hc {
    -webkit-box-pack: center;
    -webkit-justify-content: center;
    -moz-justify-content: center;
    -ms-justify-content: center;
    -o-justify-content: center;
    justify-content: center;
}

.flex-hr {
    -webkit-justify-content: flex-end;
    -moz-justify-content: flex-end;
    -ms-justify-content: flex-end;
    -o-justify-content: flex-end;
    justify-content: flex-end;
}

.flex-hl {
    -webkit-justify-content: flex-start;
    -moz-justify-content: flex-start;
    -ms-justify-content: flex-start;
    -o-justify-content: flex-start;
    justify-content: flex-start;
}

.flex-ec {
    -webkit-justify-content: space-between;
    -moz-justify-content: space-between;
    -ms-justify-content: space-between;
    -o-justify-content: space-between;
    justify-content: space-between;
}