.screen {
    padding:            20px;
    box-sizing:         border-box;
    min-height:         105vh;
    padding-top:        500px;
    transition:         opacity 2s;
    text-align:         center;
}

#wrapper > div:last-child {
    min-height:         100vh;
}

#screen2 {
    background:         #eee;
}

.header {
    position:           fixed;
    width:              100%;
    z-index:            5;
}
 
#wrapper {
    position: fixed;
    top: 0;
    left: 0;
    bottom: 0;
    right: 0;
    overflow: auto;
}

#screen2 span {
    margin-left: 10px;
    border: 2px solid blue;
    padding: 10px 14px;
    border-radius: 40px;
    transition:         margin-left 4s;
}