body {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  margin: 0;
}
.container {
  width: 500px;
  height: 500px;
  background-color: black;
  position: relative;
  overflow: hidden;
  rotate: 45deg;
}
.child,
.child-2 {
  position: absolute;
  background: radial-gradient(circle at 45%, brown, green);
  bottom: 0;
  left: 0;
  right: 0;
  top: 0;
}
@keyframes spin {
  from {
    transform: rotate(0deg);
  }
  to {
    transform: rotate(360deg);
  }
}
.child-1 {
  animation: spin 5s linear infinite;
}

.child-2 {
  inset: 10px;
  background-color: transparent;
  z-index: 10000;
  display: flex;

  flex-wrap: wrap;
  gap: 10px;
}
.child-2 > div {
  width: calc(50% - 10px);
  height: 40%;
  background-color: purple;
  justify-content: center;
  align-items: center;
}
.child-2 > div > div {
  rotate: -45deg;
  font-size: 25px;
}