Use pure CSS to create a pulsating loader effect source code

<div class="loader">
    <span></span>
    <span></span>
    <span></span>
    <span></span>
    <span></span>
    <span></span>
    <span></span>
    <span></span>
    <span></span>
    <span></span>
</div>

body {
    margin: 0;
    height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(#eee 70%, pink);
}

.loader {
    width: 6em;
    height: 6em;
    padding: 3em;
    font-size: 10px;
    background-color: pink;
    border-radius: 50%;
    border: 0.8em solid hotpink;
}

.loader {
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.loader > span {
    width: 0.5em;
    height: 50%;
    background-color: deeppink;
}

.loader > span {
    transform: scaleY(0.05) translateX(-0.5em);
    animation: span-animate 1.5s infinite ease-in-out;
}
@keyframes span-animate {
    0%, 100% {
        transform: scaleY(0.05) translateX(-0.5em);
    }
    15% {
        transform: scaleY(1.2) translateX(1em);
    }
    90%, 100% {
        background-color: hotpink;
    }
}

.loader > span {
    animation-delay: calc(var(--n) * 0.05s);
}

.loader > span:nth-child(1) { --n: 1; }
.loader > span:nth-child(2) { --n: 2; }
.loader > span:nth-child(3) { --n: 3; }
.loader > span:nth-child(4) { --n: 4; }
.loader > span:nth-child(5) { --n: 5; }
.loader > span:nth-child(6) { --n: 6; }
.loader > span:nth-child(7) { --n: 7; }
.loader > span:nth-child(8) { --n: 8; }
.loader > span:nth-child(9) { --n: 9; }
.loader > span:nth-child(10) { --n: 10; }

.loader {
    animation: loader-animate 1.5s infinite ease-in-out;
}
@keyframes loader-animate {
    45%, 55% {
        transform: scale(1.05);
    }
}