<main>
    <div class="atom">
        <div class="electron"></div>
        <div class="electron-alpha"></div>
        <div class="electron-omega"></div>
    </div>
</main>

<footer>
    <a href="https://twitter.com/alterebro" target="_blank" title="Jorge Moreno. Front End Web Developer and UI Designer">@alterebro</a>
</footer>

:root {
    --atom-size: 180px;
    --atom-color-hex: #00d8ff;
    --atom-color-rgb: 0, 216, 255;
    --nucleus-size: calc(var(--atom-size) / 5);
    --electron-color-hex: #99f8ff;
    --electron-size : calc(var(--atom-size) / 25);
    --electron-orbit-size : calc(var(--atom-size) / 2.5);
    --electron-speed : 1.2s;
    --electron-speed-alpha : 1s;
    --electron-speed-omega : .8s;
}

html, body {
    margin: 0;
    padding: 0;
    width: 100%;
    height: 100%;
    overflow: hidden;
    background: #1f1f1f;
}
body {
    display: grid;
    place-items: center;
    box-sizing: border-box;
}
*, *:before, *::after { box-sizing: border-box; }


/* Atom */
.atom {
    position: relative;
    width: var(--atom-size);
    height: var(--atom-size);
    animation: 8s atom infinite cubic-bezier(1, .25, 0, .75);
}
@keyframes atom {
    0% {    transform: rotate(0deg) scale(1); }
    12.5% { transform: rotate(-45deg) scale(.9); }
    25% {   transform: rotate(-90deg) scale(1); }
    37.5% { transform: rotate(-135deg) scale(.9); }
    50% {   transform: rotate(-180deg) scale(1); }
    62.5% { transform: rotate(-225deg) scale(.9); }
    75% {   transform: rotate(-270deg) scale(1); }
    87.5% { transform: rotate(-315deg) scale(.9); }
    100% {  transform: rotate(-360deg) scale(1); }
}

/* Nucleus */
.atom::before {
    content: '';
    display: block;
    position: absolute;
    top: 50%;
    left: 50%;
    width: var(--nucleus-size);
    height: var(--nucleus-size);
    margin-top: calc(var(--nucleus-size) / -2);
    margin-left: calc(var(--nucleus-size) / -2);
    background: var(--electron-color-hex); /* var(--atom-color-hex); */
    border-radius: 100%;
    box-shadow: 0 0 3px 0 var(--atom-color-hex);
    animation: 2s nucleus infinite cubic-bezier(.65, 0, .35, 1);
}
@keyframes nucleus {
    0% { transform: scale(1); }
    25% { transform: scale(.9); }
    50% { transform: scale(1); }
    75% { transform: scale(.85); }
    100% { transform: scale(1); }
}

/* Electron Orbit */
.atom > [class^="electron"] {
    border-top: solid rgba(var(--atom-color-rgb), .5) 1px;
    border-right: solid rgba(var(--atom-color-rgb), .35) 2px;
    border-bottom: solid rgba(var(--atom-color-rgb), .2) 4px;
    border-left: solid rgba(var(--atom-color-rgb), 0) 2px;
    border-radius: 100%;
    width: 100%;
    height: var(--electron-orbit-size);
    position: absolute;
    top: 50%;
    margin-top: calc(var(--electron-orbit-size) / -2);
    animation: var(--electron-speed) electron-orbit infinite linear;
}
.atom > .electron-alpha {
    transform: rotate(60deg);
    animation: var(--electron-speed-alpha) electron-orbit infinite linear;
}
.atom > .electron-omega {
    transform: rotate(-60deg);
    animation: var(--electron-speed-omega) electron-orbit infinite linear;
}
@keyframes electron-orbit {
    0% {
        border-top: solid rgba(var(--atom-color-rgb), .5) 1px;
        border-right: solid rgba(var(--atom-color-rgb), .35) 2px;
        border-bottom: solid rgba(var(--atom-color-rgb), .2) 4px;
        border-left: solid rgba(var(--atom-color-rgb), 0) 2px;
    }
    25% {
        border-top: solid rgba(var(--atom-color-rgb), .35) 1px;
        border-right: solid rgba(var(--atom-color-rgb), .2) 2px;
        border-bottom: solid rgba(var(--atom-color-rgb), 0) 4px;
        border-left: solid rgba(var(--atom-color-rgb), .5) 2px;
    }
    50% {
        border-top: solid rgba(var(--atom-color-rgb), .2) 1px;
        border-right: solid rgba(var(--atom-color-rgb), 0) 2px;
        border-bottom: solid rgba(var(--atom-color-rgb), .5) 4px;
        border-left: solid rgba(var(--atom-color-rgb), .35) 2px;
    }
    75% {
        border-top: solid rgba(var(--atom-color-rgb), 0) 1px;
        border-right: solid rgba(var(--atom-color-rgb), .5) 2px;
        border-bottom: solid rgba(var(--atom-color-rgb), .35) 4px;
        border-left: solid rgba(var(--atom-color-rgb), .2) 2px;
    }
    100% {
        border-top: solid rgba(var(--atom-color-rgb), .5) 1px;
        border-right: solid rgba(var(--atom-color-rgb), .35) 2px;
        border-bottom: solid rgba(var(--atom-color-rgb), .2) 4px;
        border-left: solid rgba(var(--atom-color-rgb), 0) 2px;
    }
}

/* Electron Unit */
.atom [class^="electron"]::after {
    content: '';
    display: block;
    width: var(--electron-size);
    height: var(--electron-size);
    background: var(--electron-color-hex);
    border-radius: 50%;
    margin-top: calc(var(--electron-size) / -2);
    position: absolute;
    top: 50%;
    left: calc(var(--electron-size) / -1);
    transform: scale(1);
    animation: calc(var(--electron-speed) * 2) electron infinite ease-in-out;
}
.atom .electron-alpha::after { animation: calc(var(--electron-speed-alpha) * 2) electron infinite ease-in-out; }
.atom .electron-omega::after { animation: calc(var(--electron-speed-omega) * 2) electron infinite ease-in-out; }
@keyframes electron {
    0% {
        left: calc(var(--electron-size) / -1);
        transform: scale(1);
    }
    12.5% {
        top: 100%;
        transform: scale(1.5);
    }
    25% {
        left: 100%;
        transform: scale(1);
    }
    37.5% {
        top: 0%;
        transform: scale(.25);
    }
    50% {
        left: calc(var(--electron-size) / -1);
        transform: scale(1);
    }
    62.5% {
        top: 100%;
        transform: scale(1.5);
    }
    75% {
        left: 100%;
        transform: scale(1);
    }
    87.5% {
        top: 0%;
        transform: scale(.25);
    }
    100% {
        left: calc(var(--electron-size) / -1);
        transform: scale(1);
    }
}

/* Shadow */
main { position: relative; }
main::after {
    content: '';
    display: block;
    position: absolute;
    top: 115%;
    left: 0;
    width: var(--atom-size);
    height: var(--nucleus-size);
    background-image: radial-gradient(closest-side, rgba(0, 0, 0, .5), rgba(0, 0, 0, 0));
    border-radius: 100%;
    transform: scale(1, .8);
    animation: 8s shadow infinite cubic-bezier(1, .25, 0, .75);
}
@keyframes shadow {
    0% {    transform: scale(1, .8) translateY(0); }
    12.5% { transform: scale(.7, .7) translateY(-20px); }
    25% {   transform: scale(1, .8) translateY(0); }
    37.5% { transform: scale(.7, .7) translateY(-20px); }
    50% {   transform: scale(1, .8) translateY(0); }
    62.5% { transform: scale(.7, .7) translateY(-20px); }
    75% {   transform: scale(1, .8) translateY(0); }
    87.5% { transform: scale(.7, .7) translateY(-20px); }
    100% {  transform: scale(1, .8) translateY(0); }
}

/* Credits */
footer {
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100%;
    height: 4rem;
    display: grid;
    place-items: center;
}
a {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Droid Sans", "Helvetica Neue", Arial, sans-serif;;
    font-size: smaller;
    font-weight: lighter;
    text-decoration: none;
    padding: .6rem .8rem;
    border-radius: .3rem;
    color: rgba(255, 255, 255, .25);
    background: rgba(0, 0, 0, 0);
    transition: all .35s ease-in-out;
}
a:hover {
    color: rgba(255, 255, 255, 1);
    background: rgba(0, 0, 0, .5);
}

// https://twitter.com/alterebro