.pack_box, .redpack_box {
    width: 100%;
    height: 100%
}

* {
    box-sizing: border-box
}

.pack_box {
    background: rgba(0, 0, 0, .7);
    top: 0;
    position: fixed;
    z-index: 1000
}

.redpack_box {
    overflow: hidden
}

.redpack_box li {
    position: absolute;
    animation: all 3s linear;
    top: -100px
}

.redpack_box li a {
    display: block
}