.hero-bg {
    position: relative;
    width: 100%;
    background: linear-gradient(180deg, rgba(115,199,234,1) 60%, rgba(255,255,255,1) 100%);
    overflow: hidden;
}

    .hero-bg .air {
        position: absolute;
        bottom: 0;
        left: 0;
        width: 100%;
        height: 100px;
        background: url(images/wave.png);
        background-size: 1000px 100px
    }


        .hero-bg .air.air1 {
            animation: wave 30s linear infinite;
            z-index: 3;
            opacity: 1;
            animation-delay: 0s;
            bottom: 0;
        }

        .hero-bg .air.air2 {
            animation: wave2 15s linear infinite;
            z-index: 2;
            opacity: 0.5;
            animation-delay: -5s;
            bottom: 10px;
        }

        .hero-bg .air.air3 {
            animation: wave 30s linear infinite;
            z-index: 1;
            opacity: 0.2;
            animation-delay: -2s;
            bottom: 15px;
        }

        .hero-bg .air.air4 {
            animation: wave2 5s linear infinite;
            z-index: 0;
            opacity: 0.7;
            animation-delay: -5s;
            bottom: 20px;
        }

@keyframes wave {
    0% {
        background-position-x: 0px;
    }

    100% {
        background-position-x: 1000px;
    }
}

@keyframes wave2 {
    0% {
        background-position-x: 0px;
    }

    100% {
        background-position-x: -1000px;
    }
}