:root {
  --montagne: #bba;
    overflow: hidden;
}

#soleil {
  background-image: radial-gradient(white, yellow 10%,  transparent 50%);
  height: 60px;
  width: 60px;
  position: relative;
  left: 400px;
  animation-name: soleil;
  animation-duration: 15s;
  animation-iteration-count: infinite;
  animation-timing-function: linear;
  transform-origin: 0px 300px;
  /*z-index: 1;*/
}


main {
  overflow: hidden;
  width: 1000px;
}

#ciel {
  background: cornflowerblue;
  height: 200px;
  animation-name: ciel;
  animation-duration: 15s;
  animation-iteration-count: infinite;
  animation-timing-function: linear;
  }

#terre {
  background: var(--montagne);
  height: 50px;
  display: flex;
}

.montagne{
  height: 200px;
  width: 200px;
  background: var(--montagne);
}

.montagne:first-child {
  transform:  skewX(10deg) scale(1.4, 1) rotate(45deg) translate(-50px, -130px);
  background-image: radial-gradient(circle at top left,white, transparent 30%);
}

.montagne:nth-child(2) {
   transform:  rotate(45deg) translate(0, -100px);
   background-image: radial-gradient(circle at top left,white, var(--montagne) 20%);
}

.montagne:nth-child(3) {
  background-image: radial-gradient(circle at top left,#fff 5%, var(--montagne) 30%);
  transform:  scale(1.7, 1.2) rotate(45deg) translate(-10px, -100px);
}

.montagne:nth-child(4) {
   transform:  skewX(20deg)  rotate(45deg) translate(0, -100px);
   background-image: radial-gradient(circle at top left,white, var(--montagne) 20%);
}

.montagne:nth-child(5) {
  transform:  skewX(-10deg) scale(1.7, 1) rotate(45deg) translate(-40px, -50px);
  background-image: radial-gradient(circle at top left,#fff , var(--montagne) 20%);
    }

@keyframes soleil{
  0% {
    transform: rotate(-90deg);
  }
  100% {
    transform: rotate(90deg);
  }
}

@keyframes ciel {
  0% {
    background-color: black;
  }
  20% {
    background-color: #648;
  }
  40% {
    background-color: cornflowerblue;
  }
  60% {
    background-color: cornflowerblue;
  }
  80% {
    background-color: #648;
  }
  100% {
    background-color: black;
  }
}