css-gradient-floating/gradient.css

@import url("https://fonts.googleapis.com/css2?family=Commissioner:wght@100;200;300;400;500;600;700;800;900&display=swap");

* {
  font-family: "Commissioner", sans-serif;
}

@keyframes red {
  from {
    left: -250%;
    top: -300%;
  }

  25% {
    left: -240%;
    top: -130%;
  }

  50% {
    left: -100%;
    top: -120%;
  }

  75% {
    left: -160%;
    top: -230%;
  }

  to {
    left: -250%;
    top: -300%;
  }
}

@keyframes blue {
  from {
    left: -280%;
    top: -80%;
  }

  25% {
    left: -180%;
    top: -100%;
  }

  50% {
    left: -120%;
    top: -250%;
  }

  75% {
    left: -250%;
    top: -300%;
  }

  to {
    left: -280%;
    top: -80%;
  }
}

@keyframes green {
  from {
    left: -180%;
    top: -100%;
  }

  25% {
    left: -120%;
    top: -250%;
  }

  50% {
    left: -250%;
    top: -300%;
  }

  75% {
    left: -280%;
    top: -80%;
  }

  to {
    left: -180%;
    top: -100%;
  }
}

@keyframes background {
  from {
    background-color: #ff5c5c;
  }

  25% {
    background-color: #9395ff;
  }

  50% {
    background-color: #fff393;
  }

  75% {
    background-color: #534eff;
  }

  to {
    background-color: #ff5c5c;
  }
}

body {
  height: 100vh;
  margin: unset;
  background: #222;
}

main {
  height: 100%;
  display: flex;
  flex-direction: column;
}

#authentication {
  width: 40vw;
  margin: auto auto;
}

#authentication > h1 {
  margin: unset;
  color: #fff;
}

#authentication > h1.header {
  width: 100%;
  height: 80px;
  padding-bottom: 0.3ex;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 1.8em;
}

#authentication > h1.header.gradient {
  z-index: -2000;
  position: relative;
  overflow: hidden;
  animation-duration: 65s;
  animation-name: background;
  animation-iteration-count: infinite;
  background-repeat: no-repeat;
  animation-timing-function: ease-in-out;
}

#authentication > h1.header.gradient > div {
  z-index: -1000;
  width: 500%;
  height: 500%;
  position: absolute;
  animation-duration: 25s;
  background-repeat: no-repeat;
  animation-timing-function: ease-in-out;
  animation-iteration-count: infinite;
}

#authentication > h1.header.gradient > div.red {
  animation-name: red;
  background-image: radial-gradient(
    circle,
    rgba(255, 25, 25, 1) 0%,
    rgba(0, 0, 0, 0) 35%
  );
}

#authentication > h1.header.gradient > div.blue {
  animation-name: blue;
  background-image: radial-gradient(
    circle,
    rgba(25, 25, 255, 0.6) 0%,
    rgba(0, 0, 0, 0) 35%
  );
}

#authentication > h1.header.gradient > div.green {
  animation-name: green;
  background-image: radial-gradient(
    circle,
    rgba(25, 255, 25, 1) 0%,
    rgba(0, 0, 0, 0) 35%
  );
}

#authentication > div.content {
  height: 300px;
  background: #1c1b1b;
}

@media (max-height: 400px) {
  #authentication {
    width: 80vw;
    margin: 25vh auto;
  }
}