.vehicle div{
    box-sizing: border-box;
    position: relative;
    margin: 0;
    height: 200vw;
    width: 50%;
    z-index: 10;
    left: 50%;
}

.vehicle{
    box-sizing: border-box;
    position: absolute;
    margin: 0;
    width: 100%;
    left: 0;
    overflow-x: clip;
    height: 100%;
}

#rocket{ 
    position: fixed;
    width: 7vw;
    top: 10vw;
    z-index: 1;
    font-size: 0;
}

#sky{
    height: 250vw;
}

#balloon{ 
    position: sticky;
    width: 10vw;
    top: 20vw;
    left: 50%;
    -webkit-transform: translate(-50%, -50%);
    transform: translate(-50%, -50%);
    z-index: 10;
}

#underwater{
    height: 290vw;
    top: 20vw;
}

#submarine{ 
    position: -moz-sticky;
    position: -o-sticky;
    position: -ms-sticky;
    position: -webkit-sticky;
    position: -webkit-sticky;
    position: sticky;
    width: 15vw;
    top: 20vw;
    left: 50%;
    -webkit-transform: translate(-50%, -50%);
    transform: translate(-50%, -50%);
    z-index: 10;
}