:roots {
  --color-background: #000;
  --color-first: #fff;
}

html {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  font-size: 62.5%;
}

*, *::before, *::after {
  box-sizing: inherit;
}

body {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
}

.space {
  width: 100%;
  height: 100%;
  background-color: transparent;
  position: relative;
  background-color: #000;
}

.earth {
  position: absolute;
  background-image: url('https://upload.wikimedia.org/wikipedia/commons/e/ed/Earth-EpicDay260-20150917.gif');
  background-size: contain;
  background-repeat: no-repeat;
  background-position: center;
  width: 150px;
  height: 150px;
  border-radius: 50%;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

.moon {
  position: absolute;
  background-image: url("https://images.pexels.com/photos/596134/pexels-photo-596134.jpeg");
  background-size: contain;
  background-repeat: no-repeat;
  background-position: center;
  width: 80px;
  height: 80px;
  border-radius: 50%;
  top: 0;
  left: 50%;
  transform: translateX(-50%);
}

.orbit {
  position: absolute;
  width: 250px;
  height: 250px;
  border: 1px solid transparent;
  border-radius: 50%;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
  animation: orbit 5s linear infinite;
}
  
@keyframes orbit {
  0% {
    transform: rotate(0deg) translate(-50%, -50%);
  }
  100% {
    transform: rotate(360deg) translate(-50%, -50%);
  }
}