Front-end daily combat: # 99 video demonstrates how to create a roller coaster loader with pure CSS

Results preview

Press the right "click the Preview" button to preview the current page, click on the link to full-screen preview.

https://codepen.io/comehope/pen/KBxYZg/

Interactive video

This video is interactive, you can pause the code video, editing video.

Please use chrome, safari, edge open view.

https://scrimba.com/p/pEgDAM/cagbkSL

Source code download

Daily front-end combat series full source code can be downloaded from github:

https://github.com/comehope/front-end-daily-challenges

Code Reading

Defined dom, elements contained in the container 3, representing three dots:

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

Centered:

body {
    margin: 0;
    height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(to right, silver, teal);
}

Ferris wheel diameter is defined, the other is the length of this basic measure are:

.loader {
    --diameter: 10em;
}

Defined size of the container, the width is 2 times:

.loader {
    --width: calc(var(--diameter) * 2);
    width: var(--width);
    height: var(--diameter);
}

Sharing attributes define pseudo-element:

.loader {
    position: relative;
}

.loader::before,
.loader::after {
    content: '';
    position: absolute;
    bottom: 0;
}

Orbitally bottom, while a line indicating the definition of a variable thickness:

.loader {
    --stroke-width: calc(var(--diameter) / 40);
    color: white;
}

.loader::before {
    width: inherit;
    height: var(--stroke-width);
    background-color: currentColor;
}

Draw central circular orbit:

.loader::after {
    box-sizing: border-box;
    width: var(--diameter);
    height: var(--diameter);
    border: var(--stroke-width) solid;
    border-radius: 50%;
    left: 25%;
}

Draw a dot, while the dot denotes defines a variable diameter:

.loader {
    --dot-diameter: calc(var(--diameter) / 10);
}

.loader span {
    position: absolute;
    width: var(--dot-diameter);
    height: var(--dot-diameter);
    background-color: currentColor;
    border-radius: 50%;
    bottom: var(--stroke-width);
    left: calc((var(--width) - var(--dot-diameter)) / 2);
}

For the dots increasing along a circular orbit of rotation animation:

.loader span {
    animation:
        rotating 2s linear infinite;
    --vertical-center: calc((var(--diameter) / 2 - var(--stroke-width) - var(--dot-diameter)) * -1);
    transform-origin: 50% var(--vertical-center);
}

@keyframes rotating {
    0%, 10% {
        transform: rotate(0deg);
    }

    60%, 100% {
        transform: rotate(-1turn);
    }
}

Dot increase for the animation moves:

.loader span {
    animation:
        run 2s linear infinite,
        rotating 2s linear infinite;
}

@keyframes run {
    0% {
        left: calc(var(--dot-diameter) * -1);
    }

    10%, 60% {
        left: calc((var(--width) - var(--dot-diameter)) / 2);
    }

    70%, 100% {
        left: calc(var(--width));
    }
}

Also provided is a two dot delay animation that looks like three dots next three compartments:

.loader span:nth-child(1) {
    animation-delay: 0.075s;
}

.loader span:nth-child(2) {
    animation-delay: 0.15s;
}

Finally, hidden content outside the container:

.loader {
    overflow: hidden;
}

We're done!