*
{
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
.scene
{
  position: relative;
  height: 100vh;
  background: linear-gradient(#a6d8ff, #fff, #fff);
  overflow: hidden;
}
.dark .scene
{
  background: #222833;
}
.sun
{
  position: absolute;
  top: 100px;
  left: 55%;
  transform: translateX(-50%);
  width: 100px;
  height: 100px;
  background: #fff;
  border-radius: 50%;
  box-shadow: 0 0 50px #fff;
  cursor: pointer;
  transition: 0.2s;
}
.dark .sun
{
  left: 45%;
  box-shadow: 0 0 0 #fff;
}

.dark .sun::before
{
  content: '';
  position: absolute;
  top: -20px;
  left: 20px;
  width: 100%;
  height: 100%;
  background: #222833;
  border-radius: 50%;
}
.bg
{
  position: absolute;
  bottom: 0;
  width: 100%;
  height: 280px;
  background: url(bg.png);
  animation: animateBg 25s linear infinite;
  background-size: 1500px;
  background-repeat: repeat-x;
}
@keyframes animateBg
{
  0%
  {
    background-position-x: 0px;
  }
  100%
  {
    background-position-x: -1500px;
  }
}
.car1
{
  position: absolute;
  left: -200px;
  bottom: 20px;
  max-width: 200px;
  z-index: 10;
  animation: car1 18s linear infinite;
  cursor: progress;
}
@keyframes car1
{
  0%
  {
    transform: translateX(0px);
  }
  90%,100%
  {
    transform: translateX(calc(100vw + 200px));
  }
}
.car2
{
  position: absolute;
  right: -200px;
  bottom: 50px;
  max-width: 200px;
  z-index: 9;
  animation: car2 12s linear infinite;
}
@keyframes car2
{
  0%
  {
    transform: translateX(0px) rotateY(180deg);
  }
  90%,100%
  {
    transform: translateX(calc(-100vw - 200px)) rotateY(180deg);
  }
}