style.css

@import url('https://fonts.googleapis.com/css2?family=Anybody:ital,wght@0,100..900;1,100..900&display=swap');
@import url('https://fonts.googleapis.com/css2?family=Afacad:ital,wght@0,400..700;1,400..700&family=Anybody:ital,wght@0,100..900;1,100..900&display=swap');
* {margin: 0; padding: 0;}

body {
  background: black;
  color: white;
  text-align: center;
}

#background {
  position: fixed;
  width: 100%;
  height: 100%;
  background: radial-gradient(#FFFFFF, #C6A0F6);
}

#page {
  background: linear-gradient(45deg, #D9B2B2, #96A9EB);
  display: inline-block;
  width: 90vw;
  border-radius: 10px;
  
  position: fixed;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);

  box-shadow: 0px 0px 10px 10px #000000AA;
}

.header {
  font-family: "Anybody", sans-serif;
}

.content {
  font-family: "Afacad", sans-serif;
}

.box {
  display: block;
  margin: 5px;
  
  background: #000000AA;
  border-radius: 10px;
  padding: 1.3rem;

  font-size: 2rem;
  font-weight: 900;
}

.row {
  display: flex;
  flex-direction: row;
}

.hidden {
  position: relative;
}

.hidden::before, .hidden::after {
  content: "";
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
  background: #203050;
  border-radius: 5px;
  transition: opacity ease-in 0.3s;
}

.hidden::before {
  z-index: -1;
  background: purple;
}

.hidden:hover::after {
  opacity: 0;
}

.fill {
  flex: 1;
}