body { background-color: white;}
#hoop {
    position: absolute;
    bottom: 0;
    left: 50%;
    width: 160px;
    height: 90px;
    margin-left: -80px;
    background-image: url(http://images.clipartpanda.com/hoop-clipart-basketball-hoop.png);
    background-color: transparent;
    background-size: cover;
}
#basketball {
    position: absolute;
    top: 0;
    left: 0;
    width: 100px;
    height: 100px;
    background-color: yellow;
    transition: transform 0.5s;
    background-color: transparent;
    background-image: url(https://upload.wikimedia.org/wikipedia/commons/thumb/7/72/Basketball_Clipart.svg/150px-Basketball_Clipart.svg.png);
    background-size: cover;
}
.poof {
    transform: scale(0,0);
}
h1, p { text-align: center; color: #900; }
.hide { display: none; }
.show { display: block; }