* {
  box-sizing: border-box;
  padding: 0;
  margin: 0;
}
body {
  min-height: 100vh;
  background: #403c3c;
  /* center in the viewport */
  display: grid;
  justify-content: center;
  align-content: center;
}
/* on the svg element set up a default value for the --stroke-dash and --stroke-dash-negative attributes
46 roughly being the length of the longest path.air
*/
body > svg {
  width: 600px;
  height: auto;
  --stroke-dash: 46;
  --stroke-dash-negative: -46;
}
/* animate the car to move slightly forwards and backwards */
g#car {
  transform: translateX(-3px);
  animation: translate 2s ease-in-out infinite;
}
/* animate the shadow to skew  toward the left */
path#shadow {
  animation: skew 2s ease-in-out infinite;
}
/* animate the wheels to spin  clockwise*/
g.wheels use {
  animation: rotate 2s linear infinite;
}
/* animate the dashes of air to briefly show them and then hide them from view */
path.air {
  /* starting from the values described by the --stroke-dash property
  ! the property is updated for each path in the script
  */
  stroke-dasharray: var(--stroke-dash);
  stroke-dashoffset: var(--stroke-dash);
  /* ! the delay of the animation is also set up in the script  */
  animation: offset 2s linear infinite;
  /* opacity to hide the obnoxious dots otherwise shown on firefox and edge */
  opacity: 0;
}

/* keyframe animations
! be sure to have the animations overlap as to show a realistic behavior
- as the car moves right the wheels spin faster, the shadow skews left, the dashes of air appear in sequence
- as the car moves left the wheels spin slower while the shadow returns to its resting place
*/
@keyframes translate {
  50% {
    transform: translateX(3px);
  }
  100% {
    transform: translateX(-3px);
  }
}
@keyframes skew {
  50% {
    transform: skewX(-20deg);
  }
}
@keyframes rotate {
  50% {
    transform: rotate(4turn);
  }
  100% {
    transform: rotate(6turn);
  }
}

/* beside animating the stroke-dashoffset property rapidly change the opacity to show the dashes and hide them when they are removed by changing the offset property
otherwise the dashes would still be partially visible on firefox and edge (at least)
*/
@keyframes offset {
  1% {
    opacity: 1;
  }
  15% {
    stroke-dashoffset: 0;
    opacity: 1;
  }
  24% {
    opacity: 1;
  }
  25% {
    opacity: 0;
    /* ! on chrome and firefox the calc() function allows to compute the negative value, but Edge seems to prefer having another variable instead */
    /* stroke-dashoffset: calc(var(--stroke-dash) * -1px); */
    stroke-dashoffset: var(--stroke-dash-negative);
  }
  100% {
    stroke-dashoffset: var(--stroke-dash-negative);
  }
}