*,
*::after,
*::before {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  font-family: sans-serif, system-ui, -apple-system, BlinkMacSystemFont,
    'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans',
    'Helvetica Neue';
}

a {
  -webkit-tap-highlight-color: transparent;
}

body {
  height: 100vh;
  width: 100%;
  overflow: hidden;
  background-color: #000;
}

.rectangle {
  position: fixed;
  inset: 0;
  width: 100%;
  height: 100%;
  background-color: #111;
  position: relative;
  background-size: cover;
  background-position: center;
  filter: saturate(400%);
  transition: filter 0.5s ease;

  &:hover {
    filter: saturate(800%);
  }

  &::before,
  &::after {
    content: '';
    position: absolute;
    background: linear-gradient(var(--linear-1), springgreen, violet, cyan),
      linear-gradient(var(--linear-2), springgreen, violet, cyan);
    background-blend-mode: screen;
    inset: -5px;
    z-index: -1;
    animation: rotarColor 10s ease alternate infinite both;
  }

  &::after {
    filter: blur(30px);
  }
}

@keyframes rotarColor {
  0% {
    --linear-1: 45deg;
    --linear-2: 135deg;
  }
  100% {
    --linear-1: 405deg;
    --linear-2: 495deg;
  }
}

@property --linear-1 {
  syntax: '<angle>';
  inherits: true;
  initial-value: 45deg;
}

@property --linear-2 {
  syntax: '<angle>';
  inherits: true;
  initial-value: 135deg;
}