<div class="pl">
  <div class="pl__dot"></div>
  <div class="pl__dot"></div>
  <div class="pl__dot"></div>
  <div class="pl__dot"></div>
  <div class="pl__dot"></div>
  <div class="pl__dot"></div>
  <div class="pl__dot"></div>
  <div class="pl__dot"></div>
  <div class="pl__dot"></div>
  <div class="pl__dot"></div>
  <div class="pl__dot"></div>
  <div class="pl__dot"></div>
  <div class="pl__text">Loading…</div>
</div>

*
  border: 0
  box-sizing: border-box
  margin: 0
  padding: 0

$hue: 223

\:root
  --bg: #{hsl($hue,10%,30%)}
  --fg: #{hsl($hue,10%,90%)}
  --fg-t: #{hsla($hue,10%,90%,0.5)}
  --primary1: #{hsl($hue,90%,55%)}
  --primary2: #{hsl($hue,90%,65%)}
  --trans-dur: 0.3s
  font-size: calc(16px + (20 - 16) * (100vw - 320px) / (1280 - 320))

body
  background:
    color: var(--bg)
    image: linear-gradient(135deg,hsla(0,0%,0%,0),hsla(0,0%,0%,0.2))
  color: var(--fg)
  font: 1em/1.5 "Varela Round", Helvetica, sans-serif
  height: 100vh
  min-height: 360px
  display: grid
  place-items: center
  transition: background-color var(--trans-dur), color var(--trans-dur)

.pl
  box-shadow: 2em 0 2em hsla(0,0%,0%,0.2) inset, -2em 0 2em hsla(0,0%,100%,0.1) inset
  display: flex
  justify-content: center
  align-items: center
  position: relative
  letter-spacing: 0.1em
  text-transform: uppercase
  transform: rotateX(30deg) rotateZ(45deg)
  width: 15em
  height: 15em
  &,
  &__dot
    border-radius: 50%
  &__dot
    $dur: 2s
    animation-name: shadow
    box-shadow: 0.1em 0.1em 0 0.1em hsl(0,0%,0%), 0.3em 0 0.3em hsla(0,0%,0%,0.5)
    top: calc(50% - 0.75em)
    left: calc(50% - 0.75em)
    width: 1.5em
    height: 1.5em
    &,
    &:before,
    &:after
      animation-duration: $dur
      animation-iteration-count: infinite
      position: absolute
    &:before,
    &:after
      content: ""
      display: block
      left: 0
      width: inherit
      transition: background-color var(--trans-dur)
    &:before
      animation-name: pushInOut1
      background-color: var(--bg)
      border-radius: inherit
      box-shadow: 0.05em 0 0.1em hsla(0,0%,100%,0.2) inset
      height: inherit
      z-index: 1
    &:after
      animation-name: pushInOut2
      background-color: var(--primary1)
      border-radius: 0.75em
      box-shadow: 0.1em 0.3em 0.2em hsla(0,0%,100%,0.4) inset, 0 (-0.4em) 0.2em #{hsl($hue,10%,20%)} inset, 0 (-1em) 0.25em hsla(0,0%,0%,0.3) inset
      bottom: 0
      clip-path: polygon(0 75%, 100% 75%, 100% 100%, 0 100%)
      height: 3em
      transform: rotate(-45deg)
      transform-origin: 50% 2.25em

    $dots: 12
    $zIndices: (5,4,3,2,1,1,2,3,4,5,6,6)

    @for $i from 1 through $dots
      &:nth-child(#{$i})
        $angle: 360deg / $dots * ($i - 1)
        transform: rotate(-$angle) translateX(5em) rotate($angle)
        z-index: nth($zIndices,$i)

        &,
        &:before,
        &:after
          animation-delay: $dur * (-($i - 1) / $dots)

  &__text
    font-size: 0.75em
    max-width: 5rem
    position: relative
    text-shadow: 0 0 0.1em var(--fg-t)
    transform: rotateZ(-45deg)

/* Animations */
@keyframes shadow
  from
    animation-timing-function: ease-in
    box-shadow: 0.1em 0.1em 0 0.1em hsl(0,0%,0%), 0.3em 0 0.3em hsla(0,0%,0%,0.3)
  25%
    animation-timing-function: ease-out
    box-shadow: 0.1em 0.1em 0 0.1em hsl(0,0%,0%), 0.8em 0 0.8em hsla(0,0%,0%,0.5)
  50%,
  to
    box-shadow: 0.1em 0.1em 0 0.1em hsl(0,0%,0%), 0.3em 0 0.3em hsla(0,0%,0%,0.3)

@keyframes pushInOut1
  from
    animation-timing-function: ease-in
    background-color: var(--bg)
    transform: translate(0,0)
  25%
    animation-timing-function: ease-out
    background-color: var(--primary2)
    transform: translate(-71%,-71%)
  50%,
  to
    background-color: var(--bg)
    transform: translate(0,0)

@keyframes pushInOut2
  from
    animation-timing-function: ease-in
    background-color: var(--bg)
    clip-path: polygon(0 75%, 100% 75%, 100% 100%, 0 100%)
  25%
    animation-timing-function: ease-out
    background-color: var(--primary1)
    clip-path: polygon(0 25%, 100% 25%, 100% 100%, 0 100%)
  50%,
  to
    background-color: var(--bg)
    clip-path: polygon(0 75%, 100% 75%, 100% 100%, 0 100%)