/**
<div class="bubbles-container">
    <div class="bubbles">
        <span class="animate-bubble" style="style="--i:(random value between 1 and 15);"></span>
        <span class="animate-bubble" style="style="--i:(random value between 1 and 15);"></span>
        <span class="animate-bubble" style="style="--i:(random value between 1 and 15);"></span>
        <span class="animate-bubble" style="style="--i:(random value between 1 and 15);"></span>
        <span class="animate-bubble" style="style="--i:(random value between 1 and 15);"></span>
    </div>
</div>
**/

.bubbles-container {
    background: hsl(216, 57.1%, 11%);
    min-height: 100%;
    overflow: hidden;
    position: relative;
    width: 100%;
}

.bubbles {
    position: relative;
    display: flex;
}

.bubbles span {
    border-radius: 50%;
    height: 30px;
    margin: 0 4px;
    position: relative;
    width: 30px;
    /*animation: bubble 15s linear infinite;*/
    /*animation-name: bubbleup;
    animation-timing-function: linear;
    animation-iteration-count: infinite;
    animation-duration: calc(300s / calc(var(--i) * 5));*/
}

.bubbles span:nth-child(odd) {
    background: hsl(191, 66.8%, 58.6%);
    box-shadow: 0 0 0 10px hsla(191, 66.8%, 58.6%, 0.3), 0 0 50px hsl(191, 66.8%, 58.6%), 0 0 100px hsl(191, 66.8%, 58.6%);
}

.bubbles span:nth-child(even) {
    background: hsl(339, 100%, 58.8%);
    box-shadow: 0 0 0 10px hsla(339, 100%, 58.8%, 0.3), 0 0 50px hsl(339, 100%, 58.8%), 0 0 100px hsl(339, 100%, 58.8%);
}

.animate-bubble {
    animation-name: bubbleup;
    animation-duration: calc(300s / calc(var(--i) * 5));
    animation-timing-function: linear;
    animation-iteration-count: infinite;
}

@keyframes bubbleup {
    0% { transform: translateY(100px) scale(0); }
    100% { transform: translateY(-100px) scale(1); }
}