body {
    width: 100%;
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    overflow: hidden;
}

.fondo h1 {
    font-size: 26px;
}

.burbuja{
    background-color: #191919;
    opacity: .3;
    transform: rotate(180deg);
    position: absolute;
    bottom: -150;
    animation: burbujas 3s linear infinite ;
    border-radius: 50%;
}
.burbuja:nth-child(1){
    width: 80px;
    height: 80px;
    left: 5%;
    animation-duration: 8s;
    animation-delay: 3s;
}
.burbuja:nth-child(2){
    width: 100px;
    height: 100px;
    left: 35%;
    animation-duration: 12s;
    animation-delay: 5s;
}
.burbuja:nth-child(3){
    width: 20px;
    height: 20px;
    left: 15%;
    animation-duration: 10s;
    animation-delay: 7s;
}
.burbuja:nth-child(4){
    width: 50px;
    height: 50px;
    left: 90%;
    animation-duration: 9s;
    animation-delay: 3s;
}
.burbuja:nth-child(5){
    width: 70px;
    height: 70px;
    left: 65%;
    animation-duration: 15s;
    animation-delay: 1s;
}
.burbuja:nth-child(6){
    width: 20px;
    height: 20px;
    left: 50%;
    animation-duration: 8s;
    animation-delay: 5s;
}
.burbuja:nth-child(7){
    width: 20px;
    height: 20px;
    left: 50%;
    animation-duration: 10s;
    animation-delay: 5s;
}
.burbuja:nth-child(8){
    width: 100;
    height: 100px;
    left: 52%;
    animation-duration: 14s;
    animation-delay: 5s;
}
.burbuja:nth-child(9){
    width: 65px;
    height: 65px;
    left: 51%;
    animation-duration: 7s;
    animation-delay: 2s;
}
.burbuja:nth-child(10){
    width: 40px;
    height: 40px;
    left: 35%;
    animation-duration: 9s;
    animation-delay: 4s;
}

@keyframes burbujas{
    0%{
        bottom: 0;
        opacity: 0;
    }
    30%{
        transform: translateX(30px);
    }
    50%{
        opacity: .4;
    }
    100%{
        bottom: 100vh;
        opacity: 0;
    }
}

@keyframes movimiento{
    0%{
        transform: translateY(0);
    }
    50%{
        transform: translateY(30px);
    }
    100%{
        transform: translateY(0);
    }
}